Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Paul1453 on October 29, 2015, 01:57:39 pm
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What are your favorite old pieces of gear to buy for parts cheap?
I have gotten some from old movie projectors, record players, stereos, and radios. I'm looking to get some more power transformers, output transformers, pots, vintage tubes etc. from old gear for cheap. What do you guys like salvaging parts from? I haven't tried any old real to real recorders yet. Like I said if I can get gear that has a usable power and output transformer in them for cheap any tubes etc are just a bonus. What do you guys look for?
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Hey mate, Valve ORGANS are the best source of parts and easy to convert to guitar use.
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I definitely agree with that. Unfortunately it seems everyone on Ebay knows that too and bids the stuff up to prices near what I could get new stuff for. :sad2:
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That's true. You just have to constantly watch and jump on a good deal immediately. In January I bought a Hammond AO-63 (see Timbo's pic above) for $19.
Juke box amps are good too, but there are plenty of JB restorers out there to compete with. And don't forget old PA amps.
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Here (Italy) organ amps are difficult to be found (near impossible), Juke Box sometime are disposable but at prices that I consider high, evidently there is a large number of fans, with PA amps the things are better and sometime happens to find it at interesting prices
Franco
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Lately I have been running across a lot of tube console stereo's. Picked up a zenith with 4 EL34, 2 OT's and a fine PT for $25 working. I have been stopping at thrift stores out in the sticks. I got a nice Stromburg Carlson PA with 2 6l6 for $80 after a tad of negotiation. It was used in a Church and left in-place after they got a new system. Looks brand new.
The old hammond tone cabinets go cheap and usually have a nice Alnico 12 in the top and a lof of nice iron if you just want parts. Got one for free just to pick it up.
I go to hamfests sometimes. Tubes and caps usually.
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that's what I'm talking about ED! Searched Craigslist and got an old Magnavox record player for $20. Trying to find more deals like that and especially the gear that has the transformers we need for conversion. :icon_biggrin:
Are old reel to reel tape recorder/players another good source? Do they usually have a useable OT?
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I agree, old organs, tone cabinets, film projectors, reel to reels, hifis etc. Basically anything that's not tooo fine, still usefull and or too cost prohibitive to repair.
Just don't look in my area!!! :icon_biggrin:
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:l2: Took another shot in the dark. So far, all my other purchases along these lines have yielded at least 2-3x parts value of what I paid including shipping. It's like my spidey sense starts tingling when I see a good BIN deal. So I just bought this Japanese made R-R tape recorder for $26 including shipping. If it's got a useable OT I've almost got 2x my costs right there. I was looking through parts for R-R gear and noticed high watt power resistors and other various components that led me to believe it was worth a shot. If its got a useable tube PS, I'll put another mark in my Good Deal column. So, what do you all think, missed the mark or Bulls-eye?
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People also make those into simple tape echos.
Open it up and see, if It's got a little SE amp then have fun.
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IIRC, that one will not have a PT, and the OT will be basically worthless (tiny). It uses the 50 and 35 heater volt tubes in it. However, it might have a Mullard tube in it which will pay you back. Most of the usable R-R's will cost $40 to ship, if the seller does a nice job packing.
I bought one just like it a year or so ago. The thing to look for in the pictures is the watts that it uses. If they have a PT it's usually 85/90 watts. Usable tubes also. The OT's in those things pick up PT hum like you wouldn't believe, so they have to be 3 inches at least apart. IMO, the little SE OT that Doug sells is well worth the $28, I think you get better tone with his. JUST my opinion.
Some of the PT's in them have 12 volt windings. I'm in the process of building a little amp now using that, and the 12AB5 it came with. I knocked together a circuit and liked it; it has a more Marshally/AC/DC type sound to it. Hope this helps!
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http://www.ebay.com/itm/Early-WEBCOR-tape-recorder-model-210-1-with-microphone-/231729565114?hash=item35f4288dba:g:Ze0AAOSwjVVV5JVJ (http://www.ebay.com/itm/Early-WEBCOR-tape-recorder-model-210-1-with-microphone-/231729565114?hash=item35f4288dba:g:Ze0AAOSwjVVV5JVJ)
http://www.ebay.com/itm/Vintage-Webcor-Reel-To-Reel-Tape-Recorder-TP-2005-1-/111802799948?hash=item1a07f7574c:g:gEcAAOSw3ydVpA-8 (http://www.ebay.com/itm/Vintage-Webcor-Reel-To-Reel-Tape-Recorder-TP-2005-1-/111802799948?hash=item1a07f7574c:g:gEcAAOSw3ydVpA-8)
Those are the kind you want to watch for. The first one has a nice case that you can re use as well, and it gets lots of attention ;)
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IIRC, that one will not have a PT, and the OT will be basically worthless (tiny). It uses the 50 and 35 heater volt tubes in it. However, it might have a Mullard tube in it which will pay you back. Most of the usable R-R's will cost $40 to ship, if the seller does a nice job packing.
I bought one just like it a year or so ago. The thing to look for in the pictures is the watts that it uses. If they have a PT it's usually 85/90 watts. Usable tubes also. The OT's in those things pick up PT hum like you wouldn't believe, so they have to be 3 inches at least apart. IMO, the little SE OT that Doug sells is well worth the $28, I think you get better tone with his. JUST my opinion.
Some of the PT's in them have 12 volt windings. I'm in the process of building a little amp now using that, and the 12AB5 it came with. I knocked together a circuit and liked it; it has a more Marshally/AC/DC type sound to it. Hope this helps!
OK, where were you 2 hrs ago? :sad2: Just kidding. Yeah I got one of those little SE OTs and it's mounted on my breadboard now. When you add in the shipping $12, it's about $40 for a low watt SE OT nevermind about a 15W or so PP OT. I couldn't see a speaker or output jack in any of the crappy pictures. I was hoping Hi-Fidelity markings meant more than 50C5 or 35W5 output tubes and a reasonable OT. Well live and learn. Maybe I'll still recoup my total investment in misc. parts. I hope. I'm sure my wife will say "What did you buy some more junk again?" Then I'll say "But honey, the parts alone are worth more than I paid." Then I'll hear "That's what you always say. You're saving LOTS of money buying all this junk." :l2: Later tonight, I'll post some pictures of my recent transformer lot I got for $25.50 including shipping. It appears I got two unknown but good PTs, one blown PP OT, and two chokes one medium and one high watt.
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I had went on a buying spree last winter, which is why I know that R-R. You might very well get lucky and get a nice tube out of it! I just forget anymore. The OT's in a lot of them are lay down type, but the PT are standups. The cases (the bigger ones) are quite nice plywood of some kind. I've made a couple little 5 watt combos with 8" speakers and they sound great.
I have a stack of them in the milkhouse waiting on me. The Wife is very proud.
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Looked at my notes. If it's an ep-2400, you're good, should have a made in GB Mullard tube in it - 12ax7. But no PT I believe.
Notes say stay away from 2200 series, no usable tubes at all. Pass on any that say Air King. Statesman are also pretty small cabs, which makes me think no PT.
If you see an Ekotape, grab it. Nice iron.
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Thanks John!
That's the kind of info I was looking for and to share with the forum. I've also got a notes list for Bell and Howell projectors. Which models to take a closer look at and which to skip completely. :worthy1:
B&H 16mm Model #'s: 142,179,185,202,285,302,385,399,535,630,641-644,8302(220V)
not a complete listing, but these are worth checking out.
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Looked at my notes. If it's an ep-2400, you're good, should have a made in GB Mullard tube in it - 12ax7. But no PT I believe.
Notes say stay away from 2200 series, no usable tubes at all. Pass on any that say Air King. Statesman are also pretty small cabs, which makes me think no PT.
If you see an Ekotape, grab it. Nice iron.
Well you know what they say, "If at 1st you don't succeed, try try again." With John's astute advice I'm pretty sure I did much better this time. Bam, there it is Revere T-100. That's the thing with Ebay auctions sometimes good stuff get's no attention and I can swoop in at the last second and pick it up for opening bid or just above that, and other times they bid the price to Crazytown.
That pretty much drains my weekly hobby budget, unless I actually manage to sell some things from my ever expanding junk pile. :l2:
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Looked at my notes. If it's an ep-2400, you're good, should have a made in GB Mullard tube in it - 12ax7. But no PT I believe.
If it's got a good Mullard 12AX7 in it I'll count it as a Good Deal, regardless of anything else. :icon_biggrin:
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I don't chase the flea markets, pawn shops, thrift shops and garage sales like I use to. However now that folks know I'm into that sort of thing, a lot of stuff just comes to me. I just threw away a big box of NOS tubes the other day. I paid $10 for them about 10 years ago. Problem was all that's left after I removed all the amp friendly tubes were all old tube TV tubes--nobody restores old Tube TV's. Worthless! I did pull all the tubes out of that box, before I threw it away, that AES is buying. I sent those to them and got a check from them the other day--$45
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I purcased some reel to reel recorder and record player on the cheap, but I didn't consider it on the list of favorite old gear because they have small amp inside in the order of 2.5-5W, also sometime happens that PT is an autotransformer or is in one piece with the motor windings
Franco
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Ditto on the R-to-R, but there are a few other flea market items to watch for -- intercom/callboxes and projectors.
My interesting cheap stuff:
* Voice of Music 722 R-to-R -> removed all the extra Mullard 12au7's and the motor, was left with a nice 6L6-based champ amp...no re-wiring needed. Plug into one of the inputs and hit Record. Also has speaker-outs. Best $10 I ever spent.
* Sony R-R -> very clean and well-built unit; stereo = two SE amps using 6aq5 and 12ax7. Just need another PT for the second SE. $14
* German made R-R -> similar to the Sony. $20
* Wooden hotel intercom callbox -> has a 2x6v6 amp with PT and OT. Don't know why they had that much power in such a small box. $8
* Dukane projector/record player combo -> another 2x6V6 setup with transformers. All the makings of a 5e3 for $12
* Bogen J15 PA -> almost an Ampeg Jet 12, old church PA. $30
Oh, don't forget that old radios are nice cabinets to build "living room" small amps into.
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Zipslack,
Seems like R to R deals have been good to you! These were my 1st ventures into R to R territory. My Revere buy appears to have everything I need to make a Champ 5C, with some extra parts left over. :icon_biggrin:
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Looked at my notes. If it's an ep-2400, you're good, should have a made in GB Mullard tube in it - 12ax7. But no PT I believe.
Notes say stay away from 2200 series, no usable tubes at all. Pass on any that say Air King. Statesman are also pretty small cabs, which makes me think no PT.
If you see an Ekotape, grab it. Nice iron.
You are correct, 2200 series no usable tubes or PT per say. Maybe it can be slightly modified to make a small bedroom amp from the case, speaker, tubes and tiny OT it has in it. I'll let you know if I come up with anything that remotely passes as a guitar amp so you can maybe try it on yours if you want. I have a better feeling about the Revere. I was able to locate a schematic showing a 6SJ7 and 6V6 with a real PT and hopefully good OT, before bidding on it. I'm reasonable confident I can make a Champ 5C out of that one, with little to no added expense. Or maybe something even better with another $20 worth of additional parts.
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What are your favorite old pieces of gear to buy for parts cheap?
"Something that already looks like what you want to build."
Seriously. Individual resistors and caps are the cheap part of an amp build. Chassis, enclosure and speaker cost quite a bit more. The power and output transformers will be your most expensive parts, and they're typically sized to go with each other in the specific circuit f the item you're buying, with little wiggle-room to adapt them for other use. So your biggest cost also has the least opportunity to mold into something very-different.
For instance, I bought a Valve Jr at a pawn shop (cost $75 in like-new condition). Sounded okay stock, but sounded much better plugged into a 2x12 extension cab I had made, for use with any future builds (I've decided building heads to go with my common 2x12 is the way to go for me). There are plenty of "mods" on the internet for the Valve Jr, and maybe I'll tinker it at some point. But if I do, I'll only need to swap the p.c. board for something else and populate it (no added cost for speaker, enclosure, chassis, knobs, iron, etc).
At a minimum, I'd start with something was was audio gear in its former life. I'd also expect to keep the power supply and output section largely as-is. I've learned the hard way that buying non-audio tube gear to re-use in an audio amp only results in having a bunch of non-audio junk sitting around. When you're really skillful you can repurpose non-audio stuff, but by then you have all the tools, etc and you typically re-work something you already have or got for free.
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I will agree with HBP to a major extent, but sometimes you get what are now expensive parts out of weird industrial gear.
For example, knobs are $2+ each. Buy something with 10 usable knobs for $10 and you are ahead of the game. Junk industrial gear very often yields up brackets and odd-shaped pieces of sheet metal and lockwashers and screws and single-post terminals. Once upon a time, all those things cost 25 cents each. Now, every tube socket is $2+.
Junk scopes, you have to get very cheap. There will lots of usable parts in those but tremendous numbers of non-usable parts. Lots and lots of 12AU7 tubes. 6DJ8 (much like a 12AX7 but with no 12 volt fil option and a different basing diagram. A big power transformer with half a dozen 6.3 volt windings but very low ampacity from 4 different B+ windings. Good, maybe, for a bench supply, not so good for an amp.
But there are also plenty of industrial devices that have 12AX7s and 5751s in them, as well.
A trashed hp 400 series VTVM (any of a dozen models they made) will yield: A Princeton-grade power trans, usually at least 1x, sometimes 2 qty 12AX7/5751, some nice binding posts. Even if they are smashed, there's $10-15 worth of amp-related parts.
I have some SKL audio filters that have 4-5 Telefunken 12AT7s.
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I will agree with HBP to a major extent, but sometimes you get what are now expensive parts out of weird industrial gear. ... A trashed hp 400 series VTVM (any of a dozen models they made) will yield: A Princeton-grade power trans, usually at least 1x, sometimes 2 qty 12AX7/5751, some nice binding posts. Even if they are smashed, there's $10-15 worth of amp-related parts. ...
True, except the HP 400_ A.C. VTVM's use all pentode preamp tubes... 6CB6's in the 400D, 6AK5's in the 400C, various metal octal tubes in the earlier models though sometimes a 6V6 in the power supply.
The 412A D.C. VTVM is the one with the 12AX7/5751. However, I'm very sentimental about those, given the excellent build quality and circuit function. I might have to hurt someone who ripped one apart, unless it was already beyond repair... :laugh:
But some of HP's other products have extremely high-quality parts. The problem is the types/values are suited to that circuit, and may be nothing like the values you typically see in an amp. I'd almost say the donor test equipment is your cheap way to repair other test equipment, rather than a cheap way to build an amp. I do agree that often, very high quality tubes were used in that old test gear.
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It's not a tube amp but ain't it great...
(http://p2pamps.com/binson.jpg)
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I will agree with HBP to a major extent, but sometimes you get what are now expensive parts out of weird industrial gear.
For example, knobs are $2+ each. Buy something with 10 usable knobs for $10 and you are ahead of the game. Junk industrial gear very often yields up brackets and odd-shaped pieces of sheet metal and lockwashers and screws and single-post terminals. Once upon a time, all those things cost 25 cents each. Now, every tube socket is $2+.
I'd have to admit this is my major source for these little do-dads. I don't even count them as value, but they often keep me from running out to Lowe's and paying $2 for a dozen lock nuts. Another part I like is the switch/pot combos found in a lot of this old gear. Keeps me from having to find/make another hole for a switch to go in. Does it usually look good using these odd parts in the amp? No, but it keeps me on the path to making an amp. Who really cares how the insides look when it's done if the amp sounds and plays great? I'm not trying to sell these at boutique amp prices. If I did a good job putting these parts together into something that will stand the test of time, it's unlikely anyone else will ever see them.
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It's not a tube amp but ain't it great...
(http://p2pamps.com/binson.jpg)
I like it. I kind of missed it when you put vintage classic gear that would be a sin to cannibalize in this parts thread. :l2:
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Its a pretty rare tape echo that I would never dream of tearing apart. I could build a very nice amp for what this thing is worth...
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I looked real quick at 1st, still thinking about pots/knobs/do-dads. Thought that was a scale or something on top before taking a closer look. It still works I guess?
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On the other hand, here's a fine piece of junk for parts. Looks like the seller got it for $6 at HIS garage sale. $50 delivered.
http://www.ebay.com/itm/Vintage-Flow-Corporation-Random-Signal-Voltmeter-Model-12A1-Powers-On/391302031838?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3Dbe6d5f64ec084efab05b02e745849bd3%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D231738048397 (http://www.ebay.com/itm/Vintage-Flow-Corporation-Random-Signal-Voltmeter-Model-12A1-Powers-On/391302031838?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3Dbe6d5f64ec084efab05b02e745849bd3%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D231738048397)
(http://i172.photobucket.com/albums/w32/ttm4/junk_meter_zpsdeqww1zz.png) (http://s172.photobucket.com/user/ttm4/media/junk_meter_zpsdeqww1zz.png.html)
It would be $15 if you didn't have to ship it. At a hamfest this would be a sweet buy for $15.
HBP: It's like a rackmount 412 or 413 except specialty meter. There's a valid rackmount chassis there, good parts.
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Anything old and heavy most people consider worthless junk and are more than happy to have you just take it away. Heavy usually means transformers that may or may not work for us. I'm always up for hauling away old heavy gear for someone. Even if I just end up throwing it in my own trash at home after checking it out closely. :icon_biggrin:
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That's really an excellent piece of tube junk. You could have 2-3-6 12AX7s there and the schemo might be on the web. And kind of interesting the mode of construction. I would have a hard time resisting that for $15 at a garage sale (eg; no shipping)
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Nice echorec!!
It reminds of the echolettes I used to have and now kind of regret parting with.. but they had fixed tape speeds. That one is a pretty innovative design.
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I once got a Dynaco ST 70 along with a Dynaco Pre-amp and Tuner in a homemade console for $5. The thrift store didn't want it taking up space. One 7199 tube and some coupling caps later, I turned the amp for $300. I was really tempted to make it into a bass amp, but it was just too nice to butcher.
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That's really an excellent piece of tube junk. You could have 2-3-6 12AX7s there and the schemo might be on the web. And kind of interesting the mode of construction. I would have a hard time resisting that for $15 at a garage sale (eg; no shipping)
Any idea what that hockey puck looking thing with the wires sticking out is? $33 including shipping to my location is making my trigger finger itchy. :l2:
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I believe the thing is a flow meter, so it is possibly similar to a regulator except in reverse. Gas flows against a membrane, membrane pushes/rotates a rheostat, the deflection shows up in the front panel meter. <--[wild a** guess only]
There's $50 worth of parts there. Or $40. PT looks excellent, plus its fairly clean. Worst thing that happens is you spend $10 too much. Very worth it, IMHO. And you could escape with a small cluster of 12AX7s, too.
I am intrigued by the way it is built, it looks like in the chassis openings on the left you can see two turret boards.
Looks to me like a prebuilt AB673 or other board could be swapped in there, wired up to the sockets, and this could be a rackmount amp with not much effort. Kewl.
There is obviously a seriously regulated power supply on the right and a nice line of tubes on the left.
Plus there's a very adapatable rackmount enclosure there, if that's of any interest. You could build a princeton or even a P reverb if you were willing to swing the can across the back. Somebody should buy that.
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Found out what the hockey puck is. Couldn't find a schematic, but it obviously has a usable tube PT, and possibly a useable OT. I like the separation of the PS from the signal tubes area, with lots of room to modify that area to install audio output tubes and a OT if necessary in a quiet shielded environment. $32.64 delivered is likely cheaper than I can buy a PT for and if it's got a couple of 12AX7s it's definitely a good deal. I've got an old rack mount Ibanez multi-effects box. I'll need to get a rack now to mount these things in. Thanks for the heads up!
Only other info I could find. 2-250K freq. range??? Could possibly have a seriously high quality OT.
It's mine. :icon_biggrin:
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Well done. I don't think that is an OT, I think it is a choke; but that's a nice Triad choke. I love gear like this, all Allen-Bradley pots, good sockets. Fun.
You'll thank me if you get 4 - 93% 5751's in there.
And I really like the build quality, and, as you say the separate-area layout is nice. The chassis as a test bed looks terrific. Nice.
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We'll see how it all shakes out. I might owe you a couple of parts from my junk pile for just the shipping costs. :l2:
You're probably right about that being a choke. Looks like an extremely quiet PS would be necessary when measuring very small random signals.
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Make sure you give us the tube report!
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> Could possibly have a seriously high quality OT.
Doesn't have an OT. Just the meter.
Power supply appears to be 6L6 regulated.
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Thanks for the info PRR. I was wondering what that octal in the PS was. I'm thinking that after removing the hockey puck that will be an ideal spot for a high quality OT. This will hopefully be transformed into my never to be parted with rack mounted head unit.
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Power supply appears to be 6L6 regulated.
Maybe PRR or someone else could help me understand the use of well known audio tubes as regulators in the PS. I did a Google search but didn't find the kind of clear explanation I was looking for. My adjustable HV bench supply uses 2 big audio tubes, some of the Google examples showed using 6au6,6bm8,12ax7,6v6,6l6 and others in the PS. I have seen this in a few PS designs but not so much in the PS of the guitar amps we all love. Does it have something to do with the frequency range/response of audio tubes, or is it more to do with their voltage amplification? My understanding is that audio tubes are not designed to provide lots of current, so their use in a regulated PS has me a little puzzled. Are they in there to help regulate the voltage, the current or both? :help: I truly appreciate your responses. :worthy1:
On this purchase, a good 6L6 would add $10 to my parts value count. :icon_biggrin:
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Audio amplifiers do not (almost never) need regulated voltage; there's better things to do with money.
Measurement equipment often includes regulation for consistent calibration.
The most popular series-pass tubes in regulators were 2A3 (fat audio triode) and when that went out of style, triode-strapped 6L6.
All the big audio Power tubes will pass considerable current. 6L6 with 250V on screen will max-out over 200mA.
The real issue is usually Dissipation. If you really asked a 6L6 to pass 200mA at 250V drop it would throw 50 Watts of heat, which is too-much for a 19W tube. Realistically you ask for <150mA at <150V drop. When that is not enough, find the big 'scope which had four or six 6550 bottles for pass elements.
A full tube regulator has two parts. A high-gain error amplifier (6AU6 is popular) and a big dumb pass tube (2A3, 6L6). Oh, and a glow-tube voltage reference.
In this case (RMS lab meter), unless I am missing something, there's no "big current". The meter is a LOW level (1uV) amplifier, normally to a rectifier and 0.2mA meter. This particular one "solves" a minor problem when reading RMS of a random waveform by heating a resistor and sensing the temperature rise. So it may be two high-gain amplifiers (one quite slow so low-current) plus under a Watt in the sense resistor. Still hard to see even 40mA in there.
The one octal tube in there (nice clamp) *may* be a steel 6L6. It could instead be a metal rectifier or the rare metal 6V6; or something else altogether. But you'd expect a rectifier to be with the PT and choke (or even selenium in this period).
Another possibility: getting CLEAN DC was a problem in the old days. Projector sound lamps were sometimes driven with DC rectified from a high-frequency oscillator. The metal octal could be doing something like this.
The power supply for this meter must be VERY clean, because it measures very LOW level hiss, and any hiss hum buzz or crap from the power supply contaminates the readings and makes the results dubious.
Designers breathed a big sigh of relief when clean transistors came out a few years after this beast. You could do all this with 1/10th the power, slightly better sensitivity, and a much smaller box.
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Here http://www.vintage-radio.info/heathkit/ (http://www.vintage-radio.info/heathkit/) is a listing of Heathkit kit schematics. Look up a PS-3 or PS-4 supply.
These (and dozens of others) use a "6L6" as what's called the "pass element." The earlier PS-3 used 1619 tubes because there were billions of them available war surplus and silly cheap. 6L6 has never been cheap. The raw HV is wired to the plate, the + supply output is taken from the cathode. It's called the pass tube because every volt and amp the supply supplies passes through that tube. The output of the overall supply is fed to the grid of the pass element (most often through a gain stage) such that when the output rises, it slightly turns down the pass tube and the cathode voltage falls. This results in a regulated output.
If you Google "pentode voltage regulator" you'll find lots of info.
Probably, one of the tubes near the clamped-down 6L6 will be a gas regulator (OA2, OB2, 5651, these are voltage references.
Most likely, that 6L6, being a metal one, will not be of use to you.
There is questionable need to have a voltage regulator in an amp. I suppose on a max gourmet basis, you would have one. If you were making a super duper preamp, you might have a regulator, OTOH, preamp tubes use very little current and you have easily an 80 ma tranny, so that tranny would hardly know 3-4 preamp tubes were there. So why do you need regulation? If you were making a club amp....almost no club amp has a reg PS!
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When I pointed out that that config of tubes was almost certainly a nice voltage regulator, I did not mean to imply it would be of any use to you! (Although it *could* power a preamp section, but again, why bother?) I would bet it prolly produces reg +250 volts, not +350, so it will likely not be useful.
That metal tube could be a 12A6 also. Very non useful. And yes, nice clamp!
What is kind of nice about this particular piece of junk is that if you want to ditch the reg PS, you should be able to just disconnect it, leave it in place as built and not torn apart, and do something else for your PS. It's a roomy chassis/enclosure.
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Very good synopsis here: http://www.jacmusic.com/techcorner/SBENCH-PAGES/sbench/reg1.html (http://www.jacmusic.com/techcorner/SBENCH-PAGES/sbench/reg1.html)
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Probably, one of the tubes near the clamped-down 6L6 will be a gas regulator (OA2, OB2, 5651, these are voltage references.
Most likely, that 6L6, being a metal one, will not be of use to you.
I love the neon purple glow of the 0D3s in my bench supply! Too bad I can't see them anymore with it all buttoned up. It made me want to have some of those in a Hi-Fi amp or open type head where the tubes are all up front for everyone to see. :l2:
Metal 6L6's no good as an audio output tube? I looked at the tube data sheets and didn't notice any big differences from the 6L6GC, but they could have easily eluded my untrained eye.
I'll check out those resources you guys provided and try to get a deeper understanding. Thanks!
My Army network is not liking some of those links, I'll have to try again at home. :sad2:
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Original recipe (steel) 6L6 is 19W 360V. (The oldest sheets show 21W and 400V but this was walked-back quickly.)
Later glass 6L6 have the same or slightly higher ratings.
6L6GC is a very different tube, 30W and 500V.
Nearly all 1960+s guitar amps rely on higher 6L6GC ratings.
One steel 6L6 "can" be used in a Large Champ, around 320V supply 60mA 4K-5K load and 9W output @ 10% THD.
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Audio amplifiers do not (almost never) need regulated voltage; there's better things to do with money.
Like make more amps to sell with those audio tubes. :l2:
Measurement equipment often includes regulation for consistent calibration.
Probably why the Army Commo and test gear I was familiar with often had it.
The power supply for this meter must be VERY clean, because it measures very LOW level hiss, and any hiss hum buzz or crap from the power supply contaminates the readings and makes the results dubious.
I came to the same conclusion, and it also explains all the can caps in there. I think you guys are right that this likely only has a 250V B+. Even if it had a 380-400V super clean B+, are you guys suggesting that I wouldn't necessarily want to use it? I don't really see how it would be a problem unless it was limiting the current to less than what is needed for the guitar amp circuit I decide to build.
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Original recipe (steel) 6L6 is 19W 360V. (The oldest sheets show 21W and 400V but this was walked-back quickly.)
Later glass 6L6 have the same or slightly higher ratings.
6L6GC is a very different tube, 30W and 500V.
Nearly all 1960+s guitar amps rely on higher 6L6GC ratings.
One steel 6L6 "can" be used in a Large Champ, around 320V supply 60mA 4K-5K load and 9W output @ 10% THD.
I kind of wondered why I was able to get the metal 6L6s for less than $10 including shipping, and not the glass GCs for less than $20.
I heard one guy playing Satriani on a 6L6 Champ. Made me want to explore that, but found the 6L6 design calls for 10+W resistors which I don't have any of yet. :sad2:
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Power supply appears to be 6L6 regulated.
Maybe PRR or someone else could help me understand the use of well known audio tubes as regulators in the PS.
PRR and Eleventeen covered regulated supplies thoroughly.
Why the use of "well known audio" tubes? Really, they were just "well known tubes" and an instrumentation designer would see them as "power" (big tube) or "small signal" (preamp tube) pentodes or triodes. As PRR stated, power triodes were often used as pass elements in a regulated supply (I've seen a lot of 6AS7/6080 dual power triodes used this way).
The problem with a triode is if you try to limit the plate dissipation by reducing the voltage from plate-to-cathode when you need big current pulled through it, you also limit the amount of plate current the triode can manage. The 6L6 had different-shaped characteristic curves, which allow big current at low plate-to-cathode voltage (so lower waste heat for the 6L6 compared to the power triode) as long as the screen voltage is held constant.
It is coincidental to the instrumentation designer that an audio designer likes the same feature of the same 6L6 tube to get bigger peak and RMS power output when used for an audio amp. Likewise the 12AX7 or 6AU6 is liked by both instrumentation and audio designers for their gain, or for availability of two sections (in the case of the 12A_7). But each designer applies the features of the tubes differently.
Look at each tube as a "device" with its individual strengths and shortcomings, much like the same MOSFET could be an audio power output device or a regulator series pass element...
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You don't want to install metal 6L6 tubes in a hot Super Reverb with 465 volts on the plates.
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You don't want to install metal 6L6 tubes in a hot Super Reverb with 465 volts on the plates.
Glad I didn't try putting them in my Peavey Mace pawnshop amp deal that started me on this tube amp odyssey. :laugh:
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PRR and Eleventeen covered regulated supplies thoroughly.
I agree and am thankful for their efforts! Yours too. :worthy1:
It is coincidental to the instrumentation designer that an audio designer likes the same feature of the same 6L6 tube to get bigger peak and RMS power output when used for an audio amp. Likewise the 12AX7 or 6AU6 is liked by both instrumentation and audio designers for their gain, or for availability of two sections (in the case of the 12A_7). But each designer applies the features of the tubes differently.
Look at each tube as a "device" with its individual strengths and shortcomings, much like the same MOSFET could be an audio power output device or a regulator series pass element...
I am trying to learn to do that, especially with now mostly considered worthless TV triode and pentode tubes. I'm thinking that some of these could be used for PI or other ancillary duties, freeing up 12A_7 tubes for more important duties. It will take some time, but maybe someday I'll get there. :dontknow:
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... worthless TV triode and pentode tubes. I'm thinking that some of these could be used for PI or other ancillary duties ... It will take some time, but maybe someday I'll get there. :dontknow:
Take your time. And copy what others have done with those; there are a handful of folks who've sussed out the ones that are worthwhile in a guitar amp, built something and posted the detail on the web.
You'll get there, but there is a lot to learn along the way.
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Make sure you give us the tube report!
Queue the Haters! Tube Report! Here it goes:
PS Side- 1 6L6, 2 Relay tubes, 1 6U8A, and brace yourself 1 Amperex Bugleboy Made in Holland 12AX7 !!!
Signal Side- 2 Channel Master 6BQ5s and 3 Amperex Made in USA Gold pinned 6922 !!!
Everything else in there is top of the line high quality parts as you can expect purchasing obsolete Govt research type gear.
Take a look. Thanks again eleventeen!
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Excellent! You cannot tell me that isn't a piece of first class tube junk. Over and above the parts which are worth it, IMO, you should be able to slap an AB763 board where the current turret boards are and build up an amp in record time.
Too bad about 6922s. You should be able to get at least $10 each and possibly more on ebay selling them though.
You done good!
Looking at the footprint of that grey Triad tranny...it looks more like it is like a "modulation" transformer...push-pull output for the 6BQ5s to >>500 ohms<< Too bad, but we never expected that to be a usable output tranny.
But you got those 6BQ5's, that's for sure a bonus. You have 75% of an amp there, at least in terms of construction effort.
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Excellent! You cannot tell me that isn't a piece of first class tube junk. Over and above the parts which are worth it, IMO, you should be able to slap an AB763 board where the current turret boards are and build up an amp in record time.
Too bad about 6922s.
You done good!
Looking at the footprint of that grey Triad tranny.
But you got those 6BQ5's, that's for sure a bonus. You have 75% of an amp there, at least in terms of construction effort.
Absolutely 1st class tube junk! I have seen my share of old Govt gear, so that's what got my trigger finger twitching.
This weekend's radio conversion project looks to go back on hold since this arrived. He FedEx'ed it to me!
6922s are Mil Spec Gold pinned twin triodes. Data sheet shows torture test requirements for these. They'll go into my inventory for now, awaiting further research.
A quick look showed the Triad to be a quality choke. It's a Triad C-15A Filter Regulator. :icon_biggrin:
2 6BQ5s a 12AX7 and a 6U8A sound very close to the tubes needed to make something like a Marshall or Vox 12-18W PP circuit. I'll have no problems stripping my only PP OT out of last weekends project.
I couldn't find a schematic online for this thing yet, you wouldn't have an idea where I should look would you? Otherwise, I need to proceed very carefully and cautiously in stripping her down to try to preserve the value of any parts that might be of interest to another electronics geek. Who knows, maybe someone would be happy to pay $33 for that hockey puck or other specialty (out of production) parts this may contain. A schematic would be of great help here.
One side of the front rack mount plate was slightly bent. No problem, I'll just grab my pliers and bend it back in shape like I would with any current rack mounted gear faceplate. Ahh, no not quite. It will take a BFH to bend this 1/4"+ hardened steel plate back into position. High quality parts throughout this construction. The picture of what I called the bottom is actually the top and it has it's cover. Only the bottom cover seems to be missing. Should be easy and cheap enough to get one made when I complete this conversion.
Hockey puck = Patent # 3,026,363
THERMAL ELEMENT FOR MEASURING TRUE R.M.S. OF RANDOM SIGNALS
Posted .pdf of this Patent earlier. Part of what little I could find online about this gear before purchasing.
Hoping I can maybe use key words from this to track down a schematic.
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6DJ8/6922s were very common in old Tektronix 2-man scopes and various other test gear. Some audiophiles really like them. They are high quality tubes, let there be no doubt. They are a bit problematical when you mix them up with 12A_7s because they have a different basing diagram as far as the heater goes. They cannot be run from 12 volts, they don't have that "split filament" deal that 12 A_7 have. If you have an amp with ALL 12A_7 tubes, you can swap them around ad infinitum without much care and without smoke.
I have no idea what the hockey puck is; pressure transducer, maybe.
You probably will have a near impossible time getting a schemo.
You'll have fun with that thing. I am certain of that!
As for parts, everything but the hockey puck is pretty generic. I really like that mode of construction. You're gonna get three nice high-quality turret boards out of that. Good deal.
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Not every junk gear purchase is a winner. I was itching to try a R-R purchase at the beginning of this thread. The Webcor model 2200 is a lemon. As John pointed out, no PT, no usable tubes, and a wimpy 1W OT. I might be able to make lemonade from the case, speaker, OT, and various assorted do-dads. :dontknow: Might try a wall wart and one of these: http://www.ebay.com/itm/171791044874?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/171791044874?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT) to make a little 6AU6 amp. :think1: I've got lots of those tubes.
My BAM*** Revere T-100 R-R purchase won't arrive until next week. Schemo shows I should be Good to Go on that one. That's the thing, you have to be willing to take some shots if you want to make a score. :l2:
All my premium tubes came from taking a shot on things that could have turned out to be lemons. :l2:
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Yeah, here's another thing for parts. 4-5 6DJ8's, an amazing lack of useful parts. Bleh. Of course the most useful item in the universe is a hp 438 calibrator. It is a 6550-powered push pull amp into a 500 ohm output transformer with 3-4 12AX7s in there.
http://www.ebay.com/itm/Vintage-HP-Agilent-H63-340B-Noise-Figure-Meter-Gas-Tube-Test-Set-Unit-/221927716013?hash=item33abec34ad:g:7gsAAOSw3ydVss7G (http://www.ebay.com/itm/Vintage-HP-Agilent-H63-340B-Noise-Figure-Meter-Gas-Tube-Test-Set-Unit-/221927716013?hash=item33abec34ad:g:7gsAAOSw3ydVss7G)
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Lifetime supply of 12AU7 (probably 5814s or 5963's)
http://www.ebay.com/itm/HP-HEWLETT-PACKARD-524D-ELECTRONIC-COUNTER-TUBE-TYPE-VINTAGE-MILITARY-SURPLUS-/151877236138?&_trksid=p2056016.l4276 (http://www.ebay.com/itm/HP-HEWLETT-PACKARD-524D-ELECTRONIC-COUNTER-TUBE-TYPE-VINTAGE-MILITARY-SURPLUS-/151877236138?&_trksid=p2056016.l4276)
Excellent junk piece. Historical, actually. Was just about the first electronic counter.
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I limit my shots to less than $50 including shipping. It doesn't take too many usable parts to get that back. It also pretty much rules out anything that remotely looks like a guitar amp on Ebay. Maybe if your lucky and catch a BIN within 5-10 minutes of listing from a seller who doesn't know what he has. I'm out of bullets again. :sad2:
Here's some from my watch list. These are not recommendations, and do your own research before parting with any of your hard earned money.
http://www.ebay.com/itm/231598552879?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/231598552879?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
http://www.ebay.com/itm/161862157178?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/161862157178?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
http://www.ebay.com/itm/231742279657?_trksid=p2060353.m1438.l2661&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/231742279657?_trksid=p2060353.m1438.l2661&ssPageName=STRK%3AMEBIDX%3AIT)
Maybe some of you lurkers on this thread might want to step up to the plate and take a shot? Careful though, it can become addicting. :l2:
Please let us know if you do take a shot and how it works out for you. Or if you don't want to play, only want to watch, post what you think are potentially good deals to discuss and see if one of the active players wants to take a shot on the things you find. Probably a good way to train your eye before jumping in the game.
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> no idea what the hockey puck is
Clearly described in the patent.
Needle meters read "Average" of an AC wave.
Sometimes we want "RMS". "Heating Value".
For known wave-shapes, the correction is easily calculated. Most meter scales are marked to RMS, assuming a Sine wave. The correction for triangle or square is different, but easily calculated.
Pulse waves, you need to know the duty cycle.
"Random" (hiss) waves correction can be calculated; but sometimes your "random" is not truly random.
This machine takes the "dumb" approach. RMS is heating value. So it amplifies the signal (without damage) until it is strong enough to heat a resistor appreciably. The patent describes a clever construction which measures temperature *rise* (what we really want) inside a semi-sealed can, with fairly strong output signal (for a thermocouple).
Today we use RMS chips to compute the RMS with math. Problem is "Crest Factor". RMS weights the peaks higher, but the math needs a Square, so the peaks get VERY big, and clip before the squarer, don't get accounted correctly. Resistors don't clip peaks (though the amplifier chain will).
I still think the total market for this thing was about 16. Three labs who would actually use it. 13 labs who had too much money in the budget and never really used it.
This *may* be one of the ones that got used. Those Service Master tubes do not go with the rest. SM was TV amplifiers, antennas, rotators, and then general TV supplies. The tubes sold under their brand were almost certainly bulk-contract, and probably lowest-bid. That does not mean "bad"... low-price tubes from 1970 were often excellent things.
The 6922s are very fine tubes but not for guitar amps. Hi-Fi fans use them, and often get screwed because ALL sorts of junk has been re-labeled and sold as 6DJ8. If you eBay, emphasize that these tubes have been in hibernation for 40 years and are for-sure(?) what they say they are.
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Thanks for your input PRR! I appreciate you freely sharing your wealth of knowledge with us! :worthy1:
I could clearly see overfunded Govt research lab written all over that one. I could also see parts I was seeking in there. It turned out better than I was expecting, so I'm happy. I also gather that you're telling me that there are no electronic geeks that want to buy my hockey puck. That's OK it's almost hockey season. :l2:
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This one has a PT, not sure about OT, but most likely Philips Miniwatt tubes from Holland. Likely a 6BQ5, do your own research.
http://www.ebay.com/itm/Philips-EL-3551A-Portable-Magnetophone-Reel-to-Reel-Recorder-for-Restoration/131626499497?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D34225%26meid%3Dbcea8ae3493c425989f1197f0912d86b%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D141818462177 (http://www.ebay.com/itm/Philips-EL-3551A-Portable-Magnetophone-Reel-to-Reel-Recorder-for-Restoration/131626499497?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D34225%26meid%3Dbcea8ae3493c425989f1197f0912d86b%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D141818462177)
This one's like my BAM*** but slightly more than I would want to pay.
http://www.ebay.com/itm/Vintage-Revere-reel-to-reel-tape-recorder-Model-T-204-4-Reto-Decor-Prop-Black/321807738833?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D34225%26meid%3De2dbd991443641bb896e34c82283c3a7%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D121792074693 (http://www.ebay.com/itm/Vintage-Revere-reel-to-reel-tape-recorder-Model-T-204-4-Reto-Decor-Prop-Black/321807738833?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D34225%26meid%3De2dbd991443641bb896e34c82283c3a7%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D121792074693)
Could be a Lemon:
http://www.ebay.com/itm/Vintage-Sears-3-Reel-To-Reel-Tape-Recorder-Model-7230/161860890633?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D34225%26meid%3D2cfa55284e1d4bddbbe7983aab6b792f%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D111805740537 (http://www.ebay.com/itm/Vintage-Sears-3-Reel-To-Reel-Tape-Recorder-Model-7230/161860890633?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D34225%26meid%3D2cfa55284e1d4bddbbe7983aab6b792f%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D111805740537)
Projector:
http://www.ebay.com/itm/Vintage-Kodak-Pageant-AV-126-TR-16mm-Film-Sound-Projector-Nice-Condition/361422532572?_trksid=p2047675.c100010.m2109&_trkparms=aid%3D555012%26algo%3DPW.MBE%26ao%3D2%26asc%3D34225%26meid%3D179977b38d414ee5b14a31649ea3447f%26pid%3D100010%26rk%3D9%26rkt%3D24%26sd%3D181904829536 (http://www.ebay.com/itm/Vintage-Kodak-Pageant-AV-126-TR-16mm-Film-Sound-Projector-Nice-Condition/361422532572?_trksid=p2047675.c100010.m2109&_trkparms=aid%3D555012%26algo%3DPW.MBE%26ao%3D2%26asc%3D34225%26meid%3D179977b38d414ee5b14a31649ea3447f%26pid%3D100010%26rk%3D9%26rkt%3D24%26sd%3D181904829536)
Do your research find a target and take a shot. It's fun, if not always profitable. :l2:
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Those things are OK, but by the time you are paying $60 incoming freight...with luck you get a little PT, a 12AX7, a 6V6, and a SE output tranny. More likely: a 6AU6 or two and a 6AQ5. How many Champs should a person own? With bad luck: 50C5 and 35W4 transformerless hazard.
*Some* projectors have nice amps in them. I have seen push-pull 6973 amps in RCA projectors. Din't quote me, but I believe those Kodak pageants used dual 35L6 outputs.
That's why I prefer the industrial gear. The industrial stuff usually has some sort of valid, reusable sheet metal. Most cheapo tape recs are usually built on a very purpose-built stamped steel chassis which is an "L" shaped thing not especially useful for putting in anything but the cab the tape rec came in. Usually riveted parts (which you can drill out, of course, but it's extra work and provides little reusable screws, nuts, etc;) The knobs are generally setscrew type. As it happens, I just got a R-R tape rec for $5, totally ratted out. GOOD power tranny and 6V6 of (at this moment) untested quality. For $5, OK, whatever. Cup of coffee stuff. I would not want to pay real money to have it shipped.
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Perhaps a nod to rare equipment is worthwhile. There may be some around who would really enjoy spending countless hours restoring a rare item to allow it to live and operate for another 50 years. To some, that may be an insane burden, especially where the sum of the parts is substantial and money is tight and a quick windfall can be gained.
Not everyone knows what is rare, or historic, but a little googling effort and forum exploring can be morally rewarding.
I've parted out a Wurl organ, but I have also 'saved' an organ from being dumped for its 64 mc1 Mullard 12AX7s and two KT66's. I have yet to find another such working organ, and the restoration path experience and historical insight has far outweighed any feeling of wasted effort. I also came across an unknown 'instrument' amp with GEC KT88's and nice magnetics, but otherwise not very aesthetic countenance, that could easily have been heart transplanted in to a nondescript amp. After a number of years of sleuthing, it was the catalyst for many old muso's fabulous recollections and photos of time past.
Money is money, but after enjoying this fabulous hobby for a few years there may come a time when a philanthropic act outweighs a few dollars in the pocket.
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You guys have just mention some of the issues about why I started this thread. Rational people cannot operate in the Ebay used tube amp parts market. Someone could take a blown PT, OT, on a rusty chassis with a couple of questionable at best 6V6s a worthless 12AX7 and list that making sure to mention the tube numbers. Offer it in unknown condition, as is, with no refunds and idiots would still bid it up over $120 including shipping every day of the week. That is why I was asking what other gear you like and can still get at rational prices. I had to skirt the fringe markets of projectors, R-Rs etc. just to find anything of potential value that was not bid to crazytown. I like the obsolete Govt research lab gear, which you can often get at reasonable rational prices, but then it's very heavy and costs a fortune to ship.
This last purchase was actually the most I have paid for old gear off Ebay. (No not quite, I paid $40 for my adjustable HV bench PS, and I had to drive to Oak Ridge TN to pick it up). I try to find interesting items in the $20-$30 range including shipping to take a chance on. Obviously most of those cheap items are beyond the restoration phase. But parts are parts, and good parts for cheap are hard to come by. When you stumble into some good Mullards, or Bugleboys it's just icing on the cake.
Can you recognize this picture?
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I always buy locally for that sort of stuff, haunting the local craigslist, ham sales, thrift store etc. gear turns up and usually at great prices with no shipping, and even better you can see it before you buy it. The weight of that sort of gear makes it cost prohibitive to ship, Mind you I'm in Canada and much of the stuff on ebay is in the states so shipping is more costly for me
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Demolition and clean up phase complete. We got flat bare ground to build on now and a pile of old parts. With the meter face missing there is a big hole in the front now. I think I want my PS to have at least 1 or 2 0D3's in it sitting right up front in the meter hole. For that beautiful neon Purple glow coming out the front. You're a crazy man, Paul! That's OK, at least I don't pay crazytown prices for junk amps on Ebay. :l2:
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Bonanza day at the CA Historical Radio Society Junkfest!
Heathkit VTVM - $5 clean
Heathkit VTVM - $5 clean
RCA BIG meter Sr Voltohmyst - FREE
Heathkit audio osc missing PT - FREE
Heathkit Harmonic Distortion meter - $5. Has a Mullard 12AX7
Tektronix dual-beam power supply for 555 scope. Has 2-3 12AX7 FREE
stereo 6BQ5 amp, no tubes $5.
$10 - 5V4 + 8 qty 12AT7 + 12AY7 all JAN ($3 for the danged 12AY7, the others were 50 cents)
Pile of transformers, mostly small power FREE
They have a great collection of old "drug store"tube testers.
(http://i172.photobucket.com/albums/w32/ttm4/ttester_zpsnxvszokx.png) (http://s172.photobucket.com/user/ttm4/media/ttester_zpsnxvszokx.png.html)
Your choice when using the zombie carcass of an old meter is either to get 2-3 OC3's (prefer OA3 75 volt) ---the neon colored ones lit up and showing in the big hole, OR, to get the meter to indicate as you play through the amp. Nothing else is acceptable!
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Nice score. I'm kind of antisocial in person and don't really like to go out beating the bushes trying to find stuff. It can be OK once in a while, but it's kind of like being drug along shopping all day by the wife. Not much fun when you don't get anything.
I've already half-assed mounted a socket in the too big cap hole in the window and placed an 0D3 in it. I've sussed out the PT voltages, looks like it was designed for +250V B+. It was mega complicated with a SS bridge, a relay, a choke, adjustment pots and way too many cap cans. Bulldozed it to the ground and am starting from scratch. I was a repair tech not an engineer/designer so I'm in over my head but very much wanting to learn. Would you be willing to guide me? I'll go get my PT notes, and let you know what my Ideas are for this never to be sold amp. If you would I'd appreciate it, as Googling/Reading/trying to figure out the PSU software and how it all fits together with my circuit choices is quite time consuming and overwhelming. :worthy1:
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Well this was a radio-electronics junkfest, so I knew I'd get something or other.
As for building a new amp, the way it's done is to simply copy older Fender (or other) amps. There are 5+ ways to go with this pile of stuff.
If the PT isn't set up to deliver 350 volts, you're probably going to either need to replace the PT, or, go with those 6BQ5s as they can run well on much lower volts than say a Deluxe. That's your first limiting factor. No reason why a Fender running 6V6 tubes cannot be adapted to drive 6BQ5s.
The very simple way is to get an AB763 (or....5E3 Deluxe or Bandmaster board from Doug) and populate it. Replace any of the 7 pin sockets with 9 pins.
Or you could copy an old Fender ckt and build the thing on those nice turret boards that came in the meter.
IMO, step 1 is to power up the power transformer and see what your HVAC winding produces. And sort out the secondary winding wires. It's desirable to measure output volts from red to red-yellow, that way you are only measuring half the winding and you won't exceed to 600 volt max on many meters. That meter did not have a "5--" rectifier so you likely have no 5 volt winding on it anyway.
Double that number (of volts) and multiply by 1.4. With a solid state rectifier, that's how many DC volts you oughta get.
And do you want to use this chassis for experimentation or do you want build a "final" version of an amp in it?
What are the voltage ratings you see on the electrolytic cans? If you see no 450 volts, you are probably headed to 6BQ5 land barring a PT change.
Boo hoo. Really nice 5751 broken in the Tek scope power supply. :sad2: There are actually a number of cracked tubes in the thing. White on the tube - cracked envelope. Try to pull the tube out, the glass breaks. A few broken 6080's and 6AU6 too. Don't care much, but I have never seen that unless the chassis underwent big shock, and you'd expect to see a huge ding or dent. (What's the difference?) No such ding/dent. Ah well, free. 1 qty 12AX7 left.
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Got the PT voltages. There were some 450V caps, but maybe just overspec'ed to sell for Govt research. Best secondary VAC I got is 213, so looking at 300VDC B+ max, unless you know some tricks. 2 separate 6V secondaries.
Definitely gonna use the 6BQ5's, I've got two premium ones of those. What I envisioned/wanted to do was to have multiple amp circuits built in this box. Change amps with the turn of one of the rotary switches it came with. BQ's for 9 pin, 6V6 or 6L6 for 8 pin, and 6AQ5's for 7 pin. Three totally different sounding amps at the turn of a switch. Not sure I can use the 6L6 now. Wanted to do PP config with all three using the only PP OT I've got now. I think it is about 15W and that would probably be too loud for my family at that level. Maybe we can figure out how to use a single metal can 6L6 SE output using the same OT as the others. Would like to use the 6L6 over the 6V6, as the 6AQ5 is kind of a smaller better sounding clone of the 6V6. IMO
Not everything would get designed and built right away. Planned on getting a sweet sounding BQ PP circuit set 1st. Then evaluate real estate available and figure out how to use the same preamp setup with the 6L6, or 6AQ5s. Get that squared away and then look at adding the 3rd amp option. There is lots of room in there, and the goal is to learn many new things as I progress to the ultimate triple header amp. :think1:
Too ambitious? I like to set a big goal to work towards, as I can always scale it back if it proves to be unachievable in my lifetime. :l2:
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I was incorrect when I said "Double that number (of volts) and multiply by 1.4. With a solid state rectifier, that's how many DC volts you oughta get."
No, it's half that. 1.4 times half the HVAC winding. .707 times the full winding.
Ergo, a Super Reverb has a 360-0-360 tranny and produces a B+ of 1.4 times 360 = 504 less the drop across the tube rectifier (you won't have such a drop since you have no 5 v winding and thus won't be using a tube rectifer...with THIS PT) = 460 odd volts.
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0D3s can regulate up to 150V, and mine have a nice purple glow which is my favorite. So I'll need 2 of them instead of 3 or 4 0A3s. Still expecting to use a metal 6L6 in the PS as the pass tube, but I don't know exactly where to start with that. So I'm expecting to use ar least 3 octal tubes and the nice locking pot that was in the original circuit after the SS FW bridge rectifier. Any other tubes needed in the PS? I'm thinking I could adjust the final B+ between 250-280 or so with the pot for the different output tube circuits envisioned in my triple header if need be. 6AQ and BQ5s both do fine with +250 VDC, and I think the 6L6 output would like me pushing something closer to the limits of my PT near +280V for B+. Any ideas for an example of a PS something like that? :think1:
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.... Still expecting to use a metal 6L6 in the PS as the pass tube, but I don't know exactly where to start with that. ... Any other tubes needed in the PS? ...
If you wanted to keep the regulated power supply in that 12A1 voltmeter, then you should have left that area un-stripped, or at least acquired/drawn a schematic of it before stripping.
However, if you're correct about 300vdc being all you'll get from the PT once rectified, then you really don't want to regulate it down further to 250vdc. Once you add decoupling for the output tube screen node, phase inverter and preamp sections, your supply voltage will start getting pretty low given the amount of signal swing you might need to drive the output tubes.
I agree with Eleventeen & PRR: if you are thinking about a complete guitar amp, then pick a model with a similar B+ for the output section (likely an EL84 amp), and copy what it has.
Got the PT voltages. There were some 450V caps, but maybe just overspec'ed to sell for Govt research. Best secondary VAC I got is 213, so looking at 300VDC B+ max, unless you know some tricks.
450v caps were over-spec; commercial companies don't do that (and stay in business). In one of your photos, I saw 6x solid-state rectifiers. 4 looked like they were in a bridge rectifier configuration (probably to get the ~300vdc you noted). The other 2 are in series, but don't appear to be the correct orientation for a voltage doubler circuit. However, you had one can cap with a cardboard sleeve over it, which almost always indicates the case (negative) is at an elevated voltage, likely for a voltage doubler.
My guess is there was a bridge-rectified main (and regulated) supply, and perhaps 2 opposite polarity half-wave rectified supplies with at least one staked on top of the main supply. The 6L6 pass tube would have needed plate & screen voltages well above the voltage of the regulated output in order to operate.
0D3s can regulate up to 150V ... So I'll need 2 of them instead of 3 or 4 0A3s. ...
Don't look at it as "regulate up to ..." The 0D3 need 160v anode-to-cathode to fire up, and stays lit while dropping ~150v across the tube. So look at it as a "light-up resistor" in a voltage divider. You should always have a resistor in series with the 0D3 to limit current between 5mA (the minimum current at which it can stay lit) and 40mA (data sheet maximum operating current).
I know data sheets and old military books show glow discharge tubes like the 0D3 as regulators, but that's really to facilitate a simple discussion of how series and shunt regulators operate, without having a bunch of parts in a schematic diagram to confuse the novice reader. In practice, they were used as zener diodes are in regulators today: to create a defined voltage reference, against which another tube (comparator, probably the 12AX7 in your 12A1) compares an error signal (provided through the error amp, probably the 6U8 in your 12A1) while controlling the pass element (6L6 in your 12A1).
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I tend to find console radios. I was going to buy a Hammond OT a week ago and the price went up since the last time I bought them. Decided to look around for some more radios.
(http://i406.photobucket.com/albums/pp142/printer2_photo/Guitar%20Amp%2002/Thrift%20store%20radios%2001_zpsziv7oksa.jpg)
I wanted to do a 12W6 build so I picked up this console, came with the transformers and speakers on the left. P-P which surprised me, used 6AQ5's, the PT seems quite large for them. The next chasis beside it had two octal tubes so I just assumed it had a 6V6 and 5Y3 as another radio that I found years ago which was the same model of radio. To my surprise when I got home I realized they were 35L6's and there was no PT the earlier cabinet had. Guess the manufacturer did some cost cutting. The redeeming value to what was an otherwise disappointing buy is that the OT is P-P and will work for a mini plexi that I want to build. The last chassis on the left has a 6K6 in it, wanted the PT to make a little SE amp. Might use it for a P-P and feed the heaters off a switching power supply.
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I didn't have any luck finding a schematic online, unless I wanted to pay like another $30 after shipping for one. That wasn't going to happen. I could have spent some time powering it up and checking some things, without the schematic it would have been difficult to know if what I was seeing was right anyway. I tend to get anxious with new junk, and almost always end up saying to myself, "I wish I would have taken a bunch of pictures, or readings before tearing it apart." This one was fairly clean, but I also like cleaning her up as I go. That way I only get filthy dirty working on it the 1st time, after that it's much nicer to work on.
Copying well known and good sounding designs was always the plan. Except for the PS, and then always keeping in mind the compatibility of certain designs. The designs ability to be incorporated in with the others to result in the ultimate triple header amp is critical. I plan on starting with a PP BQ design with one or 2 12AX7s in the preamp. No reverb or tremolo circuits, KISS keep it simple stupid, rings in my ears. This 1st design is critical, as it is the foundation for any other circuit to be added later. It will define input and output sections, and the offboard effects loop configuration if implemented. Lots of things to consider.
I thought that starting with an all-purpose, around 250-300V, adjustable Power supply would be a good starting point. :help:
HBP, if you wanted to split this thread into two around this point that would work. Or, I could just start another thread for the ultimate triple play head build.
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... Copying well known and good sounding designs was always the plan. ...
I thought that starting with an all-purpose, around 250-300V, adjustable Power supply would be a good starting point. :help:
But you already have one of those, don't you?
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... Copying well known and good sounding designs was always the plan. ...
I thought that starting with an all-purpose, around 250-300V, adjustable Power supply would be a good starting point. :help:
But you already have one of those, don't you?
My Oregon Scientific bench supply is that and more. This piece of gear has a PT left in it, starting from there.
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The gas regulator tube thing is charmingly obsolete; if you're just looking for a visual goodie to light up, fine. They really can't regulate any significant current to speak of. The octals should not be handling above about 30 mils or they start to get life-shorteningly hot. They are/were almost always used (in tube power supplies) to regulate a little tube (typ 6AU6, 6GH6, 12AX7) whose output gates a bigger tube. (6AV5, 6L6, 5881, 6080, 6550, 2A3) For more precision, 5651 tubes were used which for some reason (possibly mfg tolerances, maybe the smaller cathode to plate distance) operated in a much tighter range than an everyday 0D3 or whatever.
One nice thing about industrial gear, as you've said, is that there is not the obsession to cut 2 cents out of mfg costs, like there was with cheapo record players and tape recs. Costs were furiously attacked and consumers must have been absolutely obsessed with prices. I have a 1964 Martin guitar price list. In that list, IIRC, an O-18 was $255, an OO-18 was $260, a OOO-18 was $265 and a D-18 was $270. The idea that one would buy an O-18 over a D-18 for a $10 or $15 price savings sounds completely absurd. (I have 2 brothers, one bought a new D-18 in 1961 and the other bot a new O-18 in 1961)
And I acknowledge, these things can certainly change over time. In the 70's and 80's Deluxe and Princeton Reverbs were simply disdained, hated. Every single music store, it seemed, had a sad and lonely $125 Deluxe Reverb for sale that sat there for years. You had to have a Twin, and if you only had a Bandmaster or Bassman you had to go to an amp guru, have him rip out the trannies, install 2 add'l 6L6 tubes and Twin iron and SS rectifier. Nowadays....if you wanted to trade for a BF or SF Deluxe, it would probably take you 2 qty Twin reverbs!
In your situation, here is probably what *I* would do: I would build a single channel 6G9 Tremolux, the early version that used 6BQ5s. http://el34world.com/charts/Schematics/files/fender/Fender_tremolux_6g9_d-fa.pdf (http://el34world.com/charts/Schematics/files/fender/Fender_tremolux_6g9_d-fa.pdf)
If you don't care about Trem, lose the trem oscillator tube. I would strip one of the turret boards you have and build it on that.
However, that design still wants close to 400 volts on the 6BQ5 plates and you either have that or you don't. >>This is certainly one of the biggest "ooops" of used tube junk: Except for TV sets, you will very often find that the power supply (meaning the power transformer) can't get over low 300 volts. If it can't, it can't, you can stare at it all day.
Some folks here like the VOX AC-30. I once had one of those and it was a fantastic amp, but the parts count in a VOX is huge.
Anyway, the Tremolux parts board is going to be virtually the same as some other build which drives 6L6 if that is your overall preference. So, if you build that and it doesn't do it for you, you can at least keep the built-up parts board and find an octal-tube amp you like better.
Before getting involved in a multi-every-which-way switchable amp, get a few simple builds under your belt. That, I would strongly advise.
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A visual goodie that hypnotizes people is a requirement. I can talk with my family and friends about this tube or that, they can listen to this design or that, and to them it's all the same. Nothing special. "Why don't you just get some new small and light stuff, instead?" :BangHead: The soothing purple glow shimmering in time with the music, now that's something they can remember and support.
I've made at least 5 different amps that worked as prototypes, so this is not completely new to me. Remember I want to approach this one step at a time, but I also know that without thinking about where I want to go to, there are many paths to take that simply end in "You can't get there from here!" Kind of like the roads in S. Korea.
The design you suggested needs a different PT. I don't really want to do that. With proper planning I think there might be some way to use what I've got, a PT with a +300V B+ max, to come up with something that could possibly power PP AQ/BQ circuits, (easy they both like +250V B+ well enough), and a lower voltage metal can 6L6 SE output circuit.
Even if I have to eventually put a 2nd OT in there, I'm OK with that. I'll even be OK with buying 2 new high quality OTs from Doug, if that is what it takes to make this dream come together into reality. That's really the point of scrounging around for cheap parts. When you need a special high quality part you've already saved enough on your other parts to just go ahead and buy that expensive part.
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PT looks beaffy enough, how about a lower voltage tube like a 6CW5? A low voltage large plate 6BQ5. Depends what you want out of the amp you could look for tubes that are designed to operate in the 170-200V range.
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PT looks beaffy enough, how about a lower voltage tube like a 6CW5? A low voltage large plate 6BQ5. Depends what you want out of the amp you could look for tubes that are designed to operate in the 170-200V range.
I've got 1 Philips MiniWatt and 1 Amperex Bugleboy both made in Holland 6BQ5s. These are both going in this amp for sure. I've got the new Amperex Bugleboy 12AX7 which came out of this, and it's going in this also. My supply of 12AX7s is very limited, only 2 more and one of those was removed from my working little Behringer AC108 amp. I have a decent amount of 12AT/AU/AVs, probably 5 of each, and like 2 of those the red tipped kind. No more premium Mullards or Bugleboys in this area. I've got 2 Mullard 6AU6s that I'm keeping for myself and would go in this if they are called for. My premium tubes are all going into this, once the bugs are worked out with less expensive stand ins.
The only tube which seems to need higher voltages is the 6L6. I've never used and don't have any EL34s. Ditto for any other big power tubes. I thought it would be interesting to have one of the three circuits use a single big output power tube for a different kind of sound. This would likely be the last circuit to add to the triple header. The other two AQ/BQ can easily be more similar in design, accepting of a lower B+, and still quite different in their resulting sound.
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PT looks beaffy enough, how about a lower voltage tube like a 6CW5? A low voltage large plate 6BQ5. Depends what you want out of the amp you could look for tubes that are designed to operate in the 170-200V range.
Working with the PS software now. T1 has the correct VAC out, not sure about it's R. L1 is the Triad choke with the right values. I can't seem to put in a pass tube, or any other tube for that matter past the rectifier spot. Just starting to experiment, but this has 283 B+ and 260 B+1. :help:
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Working with the PS software now. T1 has the correct VAC out, not sure about it's R.
Measure resistance of the secondary with the power off; write this down.
Measure the resistance of the primary. You mentioned the secondary voltage was 213vac, presumably with 120vac in. This is a 1:1.775 ratio, So multiply your primary resistance by 1.775. Add to secondary resistance, and that's the number to use in the Duncan calculator.
I can't seem to put in a pass tube, or any other tube for that matter past the rectifier spot.
That's right. It's not a full-up SPICE program, and only simulates a simple rectified power supply to tell you current (especially peak current) drawn through the rectifier, and output voltage at various supply nodes (assuming you know their individual current draw). The rest is a matter of your design ability with paper & pencil.
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Thank you HBP!
Got 1.9 r pri, 5.1 r sec. 1.9*1.775=3.3725 + 5.1 sec = 8.4725 r for T1
Changed the value in PSU, with a couple of other slight value changes downstream. Got a few more Vs out if it now. B+ = 290V and B+1 = 260V now. What to put for the Load? Estimate max current draw of all the tubes in my circuit and make the Load constant current at that level to be safe? The Triad choke is labeled for 250mA, this should be more than enough right?
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Working with the PS software now. T1 has the correct VAC out, not sure about it's R.
Measure resistance of the secondary with the power off; write this down.
Measure the resistance of the primary. You mentioned the secondary voltage was 213vac, presumably with 120vac in. This is a 1:1.775 ratio, So multiply your primary resistance by 1.775. Add to secondary resistance, and that's the number to use in the Duncan calculator.
I can't seem to put in a pass tube, or any other tube for that matter past the rectifier spot.
That's right. It's not a full-up SPICE program, and only simulates a simple rectified power supply to tell you current (especially peak current) drawn through the rectifier, and output voltage at various supply nodes (assuming you know their individual current draw). The rest is a matter of your design ability with paper & pencil.
Could you enlighten me why the the calculations on the secondary resistance?
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An interesting link to a unique 1953 concept that may be just the ticket to add 6L6s to the triple header. :think1:
https://www.ampbooks.com/mobile/amp-technology/6L6-phase-inverter/ (https://www.ampbooks.com/mobile/amp-technology/6L6-phase-inverter/)
With lower voltage than even the 6AQ5s/6BQ5s like, in a PP Class A configuration, and a reduction in the number of tubes needed for operation? Is it all too good to be true? More research is needed, and maybe even a prototype of this unique circuit idea will need to be setup and tested on my breadboard. Who knows? Could this be the key to adding 6L6 tubes to the ultimate triple header amp? :dontknow:
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Could you enlighten me why the the calculations on the secondary resistance?
The transformer resistance acts to limit the peak current charging the first filter cap. That quantity varies with different transformers.
People like to say, "A ____ rectifier can only handle a maximum of ___uF capacitance." That's bogus; really the rectifier can only handle a maximum peak and/or steady-state current pulled through it. Bigger uF's make that peak current bigger, but bigger R (either inherent in the transformer or added via external resistors) makes that peak current smaller.
By the way, I think I forgot to have Paul square the ratio of primary to secondary voltage (so multiply Pri Ω * 1.7752 to get Sec Ω); after all, it's the same reflected impedance concept as with output transformers.
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OK, I actually got 2 more R-R after the Lemon Webcor 2200. So for a total of $50.07 including shipping I got the Revere T-100 and a Silvertone 4070. Here's some pics. Yes junk gear often has mouse droppings etc. in it. Total I netted 2 PTs 2 OTs 2 6V6s 2 6X5s 2 6SJ7s 2 5879s 1 6K6 and 1 12AX7, and various other pots, caps, resistors and assorted do-dads. Not a Mullard or Bugleboy score, but I count this as a reasonable return on investment. :icon_biggrin:
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more pics. Rechecked prices on new transformers. Conservative price without shipping PT = $60 OT = $15. So now I'm feeling better about having to deal with mouse turds. On transformers alone I've gotten a 3-1 return, and possibly kept reusable parts from ending up in a landfill somewhere. If you're building little bedroom amps to sell to your friends for cheap, you might consider buying some junk gear. If you're looking to build larger gigging type amps, and resell the amps you build to someone who needs to check them out inside and out, but they are willing to pay near full retail price, then obviously Doug's Kits are the only way to go. :icon_biggrin:
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Could you enlighten me why the the calculations on the secondary resistance?
The transformer resistance acts to limit the peak current charging the first filter cap. That quantity varies with different transformers.
People like to say, "A ____ rectifier can only handle a maximum of ___uF capacitance." That's bogus; really the rectifier can only handle a maximum peak and/or steady-state current pulled through it. Bigger uF's make that peak current bigger, but bigger R (either inherent in the transformer or added via external resistors) makes that peak current smaller.
By the way, I think I forgot to have Paul square the ratio of primary to secondary voltage (so multiply Pri Ω * 1.7752 to get Sec Ω); after all, it's the same reflected impedance concept as with output transformers.
I understand the output resistance limiting the current in the secondary, thought that PSU would have produced a reasonable approximation wit it. Never really noticed it was off all that much.
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In your post with 5 pics; the PT on that thing is simply enormous for a little tape recorder. The mfr must have gotten a good deal on those.
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That was on the Revere T-100. Just kind of took them apart and cleaned them up a bit. Thought it might have 320V for B+ (schematic shows +395 coming out the rectifier). Spent a little more time on the Silvertone, as it wouldn't even power up, but looked in reasonable condition otherwise. DeoxIT came to the rescue again, sprayed it inside the power switch/ volume pot worked it in good and she powered right up. Major hum, but it appeared to react to the volume knob.(dated 1943 tubes) Didn't even try to power up the mouse infested T-100 yet, but I did like the PT when I saw it. She's heavy. Further inspection after work tonight.
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> thought that PSU would have produced a reasonable approximation
You have to enter transformer resistance. Actually there is a default which is in a ballpark for not-small not-large tube-volt PTs, but you should consider how it fits your situation.
PSU has two ways to figure PT resistance. You can put in resistance on both sides. OR you can switch to "Regulation" and enter your PT's VA and estimated regulation. For monster amps this will be 10% to 5%. For dinky preamps it may be as high as 20%. (Double down/up transformer chains may be over 40%.) PSU will work-out the resistance for that regulation and V and A.
The default will, for many cases, throw "rectifier peak current exceeded..." messages. Especially when using grossly over-large cap values. Sometimes when actual DCR values are put in, it passes. Either way, it is the handiest way to check this otherwise mysterious cause of short-term rectifier failures.
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> thought that PSU would have produced a reasonable approximation
You have to enter transformer resistance. Actually there is a default which is in a ballpark for not-small not-large tube-volt PTs, but you should consider how it fits your situation.
PSU has two ways to figure PT resistance. You can put in resistance on both sides. OR you can switch to "Regulation" and enter your PT's VA and estimated regulation. For monster amps this will be 10% to 5%. For dinky preamps it may be as high as 20%. (Double down/up transformer chains may be over 40%.) PSU will work-out the resistance for that regulation and V and A.
The default will, for many cases, throw "rectifier peak current exceeded..." messages. Especially when using grossly over-large cap values. Sometimes when actual DCR values are put in, it passes. Either way, it is the handiest way to check this otherwise mysterious cause of short-term rectifier failures.
Just saying that I measure a transformers open voltage and secondary resistance and plug those numbers in. Never had to bother with the primary resistance and the turns ratio. I'll give them a try on my next amp.
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Just saying that I measure a transformers open voltage and secondary resistance and plug those numbers in. Never had to bother with the primary resistance and the turns ratio.
To be clear, you don't have to do more than what you've been doing.
The net result will be that entered transformer resistance is lower than the effective value for the actual part, resulting rectifier peak current will be higher than in real life, and calculated maximum safe capacitance will be lower than it could be. All that simply adds up to a conservative design, which is never a bad thing.
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Junk gear parts research and testing day. PTs and Chokes.
Attached is a pic of my 2 unknown PTs and Chokes with my notes so far.
I mapped out my unknown PTs with resistance measurements. To be safe I 1st apply 6.6VAC from my bench supply to what I believe should be the primary.
Recorded my resulting VAC measurements, and did some calculations. Now some questions maybe you can help me with?
On the PT I called Big Boy I'm expecting when I apply 120VAC to the Green and Black primary inputs:
I should get @ 390VAC between pins 1-6 and 1-10 and pin 1 is my CT
I should get @ 12VAC between pins 7--8
Pins 5-9 might be a 5VAC supply
Pins 2-3-4 might be the 6VAC CT supply
On the PT I called Little Boy I'm expecting when I apply 120VAC to the Green and Black primary inputs:
I should get @ 315VAC between pins 6-11 and 6-8 and pin 6 is my CT
I'm not sure what else to expect out of this one
Pins 1-2-3 might be a 6VAC CT supply?
Pins 4-5-Yellow wire might be a 2nd 6VAC CT supply?
Pins 7-10 ???
Pins 9-12 might be another 6VAC supply no CT???
Little Boy is a little odd in that it has Red-Green-Black primary inputs?
I would like to get some feedback from you guys before I hook up 120VAC to the primary inputs. :worthy1:
The bigger choke has 210 ohms resistance, any way to tell it's H?
The little choke has 5100 ohms resistance, any way to tell it's H?
Thanks for the help guys! :worthy1:
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> Never had to bother with the primary resistance and the turns ratio.
Double the measured secondary resistance. Pretty close.
This is commercially correct for a single-secondary sane-voltage transformer. Both windings add resistance (allow for ratio). It would be silly (and inefficient) to have low-low R in one side with high R in the other. Usually both windings take equal space (best use of window area) which with ratio-leverage gives about equal contribution to total effective resistance. So measure sec and double it.
With more than two secondaries, it gets tricky. If it were a 1,000VA transformer with a little 10VA winding for a plate supply, then the primary must be so low-R that it can be ignored. But we don't find such transformers in our amps. Typically the heater winding is somewhat smaller than the plate winding, so "double" maybe should be a factor of 1.5X or 1.7X. No great precision is needed. You will allow ample safety margins. Wall-voltage variations are greater than transformer effects.
Very high voltage windings are all paper, and may have more resistance than you expect from simple economic balance. OTOH, high voltage LOW current windings (preamps) "naturally" call for wire too thin to wind at high speed, economics suggest an over-size wire, and resistance may be low (which means the primary may have more effect, and "double" might really be 2.5X or even 3X).
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While investigating the T-100 2 prong cord it began to crumble to dust in my hand. Checking the mouse infested bottom, I decided it was safest for me and the components to just gut her and clean all the turds out of her. So the transformers came off, all components underneath got cut out, and into a hot soapy disinfectant bath she went to soak overnight. She got a scrubbing this morning, dumped the water, and gave her another hot soapy soak. After cooling she got another scrubbing, rinsing, and a towel dry. Took some pics to post and got her hanging in front of a fan for the next day or two to completely dry before I mess with her again. I'm thinking her chassis and case will still be used to make into a little Champ.
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Someone has offered me a Hammond BV. It will be a hassle to move it. Any idea what I can get out of it?
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Not sure what a BV is? Have you googled it? Lot's of people here rave over Hammond organs for conversions. It should have some good Iron and maybe even some Mullard 12AX7's. For free? I'd definitely go through the hassle to get it myself, but that's just the way I am. :l2:
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Someone has offered me a Hammond BV. It will be a hassle to move it. Any idea what I can get out of it?
I just did a quick search and it looks like that's a true 'tone wheel' Hammond with draw bars.
If so, PLEASE DON'T part it out. They are unique instruments that will never be made again.
Many players still love those. Sell it to someone who will take care of it. :icon_biggrin:
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V for Vibrato and the B is a tube organ. As Willabe pointed out this model appears to be a classic. If it can be fixed, or is in working condition now, the right buyer will pay quite a bit for it.
Waaaaay more than someone would pay for any kind of guitar amp you could make out of it. Your location would make finding the right buyer difficult. :sad2:
To the right buyer it could possibly go for $10,000 or more! :icon_biggrin:
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...... this model appears to be a classic. If it can be fixed, or is in working condition now, the right buyer will pay quite a bit for it.
Yep! :icon_biggrin:
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The offer just came today so I didn't know if anyone had some experience with them off hand. I definitely respect the idea of keeping this thing in tact. I live in Juneau so it is not likely at all that I will find someone willing to pay shipping. I doubt the thing is functional. I will need to get some more info from the guy before I make up my mind. I'm wondering if the thing is destined to rot as furniture on this island or potentially be repurposed.
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Might be someone around there that plays? A church might like it.
Be cheaper for them to pick it up from you or your friend then to have 1 shipped up there.
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> A church might like it.
It came OUT of a church. (98% likely.)
Most churches can hardly replace their light-bulbs. Maintaining (not even restoring) a tonewheel machine is far beyond their comfort zone. It was tough even when Hammond had on-call techs.
Today a Roland keyboard is a much more practical hymn machine. Gives zero trouble for a decade. When it does, a new one does not need a major fund-drive. (Play one service on a CasioTone, pass the plate, done.)
I dunno what the rock/blues scene is in Juneau but again I suspect that unless a player LOVES his tonewheels, a Roland etc is a much more practical machine. In Chicago or Nashville you may find a tonewheel guru who would add it to his repair spares and possibly love it for years to come. But unless they split the big city and move to Alaska, shipping is maybe more than they can spare.
The core tonewheel guts are worth more per pound than the case amplifier and speakers. It is not so silly to ship the guts south. Then the dog can sleep in the case and the amplifier can be re-purposed.
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It came OUT of a church. (98% likely.) Most churches can hardly replace their light-bulbs. Maintaining (not even restoring) a tonewheel machine is far beyond their comfort zone. It was tough even when Hammond had on-call techs.
Not if it was your church or mine! :icon_biggrin:
But.... I guess that's part of what it's come down to now. BUT if you've ever been in a room with a Hammond 'tonewheel machine' run through a real Leslie with a real band, man ain't that the STUFF!!!!!
That set up can coooo like a dove and whisper softness, cry like a baby and scream like an eagle, and every thing in between!
(Play one service on a CasioTone, pass the plate, done.)
:laugh: Yeah I'd throw cash money in the plate too!
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The bigger choke has 210 ohms resistance, any way to tell it's H?
The little choke has 5100 ohms resistance, any way to tell it's H?
I use this technique:
http://dalmura.com.au/projects/Choke%20measurement.pdf (http://dalmura.com.au/projects/Choke%20measurement.pdf)
I would also rate the Hammond BV as rare, and imho should not be parted out. It actually doesn't have much valve gear in it, so best to try and find someone really keen on electro-mechanical restoration, as it is likely to be an onerous job.
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Some more info on the organ. It was purchased from a Church quite a while ago... was never fired up and has been sitting in storage for several years. He stated that the finish was not in ideal condition either. I think I will take a look and maybe reach out for any local interest.
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So with the simple measurement scheme shown on page 1.
It would not be a good idea for me to try to just use my adjustable HV bench PS by tying my 6 VAC supply together with my adjustable 0-300 VDC supply and sending that through the resistors and unknown choke? 1st idea, and quickly considered not advisable. :think1:
Better to use like a small 12 VAC transformer from some broken radio or something?
Make a little FW bridge rectifier board from cheap IN4001 diodes and use that with the little 9 or 12 VAC PT to connect to this testing circuit?
I'm still reading and trying to comprehend the full paper.
I see it shows using 12, 20, 32, and 52 VAC, but the resulting L calculated appears relatively close with each.
So for a general in the ballpark estimate of the unknown chokes H value, I could get by using just a little 9 or 12 VAC PT exclusively?
Thank you for this info, trobbins! :worthy1:
The bigger choke has 210 ohms resistance, any way to tell it's H?
The little choke has 5100 ohms resistance, any way to tell it's H?
I use this technique:
http://dalmura.com.au/projects/Choke%20measurement.pdf (http://dalmura.com.au/projects/Choke%20measurement.pdf)
I would also rate the Hammond BV as rare, and imho should not be parted out. It actually doesn't have much valve gear in it, so best to try and find someone really keen on electro-mechanical restoration, as it is likely to be an onerous job.
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Coupling AC and DC supplies needs some thought as to the consequences, so the test circuit in that reference uses just a simple secondary winding and bridge rectifier setup to give a combined AC+DC test current. The main concern is that the secondary winding can supply the test current - if you want to test a choke to 100's of mA then the winding needs to cover that.
If you had a variac mains supply then you can take many measurements to construct a performance curve of the unknown choke. Otherwise you may need to cobble together a few secondary windings to give say 3-4 test AC voltages. As you don't know the inductance of the choke, then best to start at a low AC supply voltage and then increase, noting the fall off in inductance. Estimating the DC power loss, from resistance and the test DC current, you can also guess whether you are pushing the choke in to high dissipation levels.
Over the years I have tested 10's of unknown chokes, so I have some transformers in a case with banana plugs for taps just for this purpose - but I probably have a little more equipment hanging around than you. One possibility is to get a batch of old 12VAC quartz downlight transformers - they can be used for many applications, even as output transformers if they have split primaries.
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Thanks for that choke article. Interesting.
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The Silvertone R-R is now a bedroom Champ!
Troubleshooting terrible hum started at the rectifier. Should have +280 V coming out pin 8, got +200.
OK, swap in a different 6X5 still +200.
Only the cap can before the 1st resistor to be dropping that V. Change out the cap can.
It had a 40-40-40uf 300V can, I only had a 40-40uf 450V can.
OK so I just leave out the last 40uf cap to see if she's gonna work. Work???
She sounds great with only slight barely noticeable hum.
She's not very loud, but when I add my 12" 8 ohm speaker to the output jack she does much better on volume.
Put in a distortion pedal and add some gain and she's a Rockin!
Less than $25 in parts total, and my time to fix her.
Not a bad deal. Pretty sure I can get $75 for her locally the way she is now.
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Nice! :icon_biggrin:
You might want to add the 40uF cap back in? Just get a single 40uF and strap it in somehow.
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Nice! :icon_biggrin:
You might want to add the 40uF cap back in? Just get a single 40uF and strap it in somehow.
No new ones in my current inventory, might need to check my junk pile for something usable.
I'm thinking of taking it to Jeff, a local music store owner who does consignment deals for me.
He'll write me a ticket for $75 and when he sells it for whatever he gets, I come pick up my cash.
The way it sounds just as it is, I think he can turn it for $100 in a week or 2 max.
It is an all tube 6V6 12AX7 amp. Cheap enough for Mom and Dad to get their Kid a tube amp, and not too loud.
My junk pile is getting a little big, time to lighten the load and restock up on ammo. :l2:
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I got set up to safely put 120VAC into my unknown PTs.
Some results were as expected, others not so much:
Big Boy has:
380-0-380 CT on pins 6-1-10
5VAC on pins 5-9
Very good so far, now the unexpected results
2.5VAC on pins 2-4 pin 3 is CT with 1.2 VAC on each side
2.2VAC on pins 7-8 Yellow wire is CT with 1.1 VAC on each side
Little Boy has:
300-0-300 CT on pins 8-6-11
5VAC on pins 1-5 pin 2 is CT
OK so far, now the unexpected results
2.4VAC on pins 4-5 Yellow wire is CT with 1.2 VAC on each side
1.3VAC on pins 7-10
4.6VAC on pins 9-12
No 6.3VAC on either, but maybe there is a way to make that without adding a 2nd filament PT?
That is if these different voltage windings can be somehow paired up and still meet the heavy current demands of the 6.3 supply.
Any suggestions, or just get some filament PTs to go with the Boys?
I've saved more than enough to do that on these. I got this lot of 5 unknown transformers for $25.50 including shipping.
So I got the Boys with their oddball voltages, the 2 unknown chokes that appear good, and a blown PP OT.
I saw that thread with someone fixing their blown OT. I'll have to check and see if I can attempt that too.
I appreciate your suggestions on how I can use these PTs. :worthy1:
Thank you!
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Nice! :icon_biggrin:
You might want to add the 40uF cap back in? Just get a single 40uF and strap it in somehow.
I found an 8 uf 250V cap in my junk parts pile and put it in.
Maybe it has less hum now, it didn't have much to begin with after putting in that new cap can.
Before that it was a complete HHHUUUMMM amplifier.
The tiny 4" speaker it contains doesn't do well with low bass frequencies.
When you connect an external, in my case 12" speaker, both play and it seems to send the bass to the external speaker.
This thing actually sounds pretty good for recently being an old piece of junk! :icon_biggrin:
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Hi, my name is Paul and I'm a junk tube gear addict. :dontknow:
What can I do when I see gear like this? I have to buy it.
This should have Philips MiniWatts from Holland in it.
A 12AX7 or 6BQ5 Miniwatt goes for just about what I paid.
Maybe the PT is fried and all the tubes dead?
I still have to take the shot.
Hi, my name is Paul and I'm a junk tube gear addict. :l2:
A signal generator is used troubleshoot and calibrate guitar amps, right?
I'll have to see if I can fix that 1st before just harvesting its high-quality parts.
Since he had that and the old Intercom ending at the same time, what the heck I guess I'll take that too.
The transformers look to be worth $15 and maybe I saved him a few $ in shipping.
My name is Paul and I'm a junk tube gear addict. :help:
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Lost it today and bought a bunch of stuff
Paid $75 Can (about $5 US)
I was intending to go buy a AO-43 and an AO-29 the fellow had listed with tubes both for $125, The high end of what I would spend. Turned out the guy(nice guy, older , not dishonest, just disorganized ) only had the AO-29 and couldn't find or had already sold the AO-43
So I bought some other junk off him to make the trip worthwhile:
-Got the AO-29 with tubes
-A mystery guitar power amp that allegedly used a unusual power tube..some 7 number ...looks like a boat anchor(anybody recognize it???)clearly used to have a cage over the tubes
-a gibbs or accutronics reverb tank in a bag(handy)
- some weird unit which is at least useful for the jacks etc
-a hammond pushpull OT
and a huge bin of old organ and hifi junk including some okay tools pots, wire, jacks, pilot lights
- 3 decent vintage 6V6Gt (now tested0 and a 12ax7 (also good)
oh and a big storage bin :icon_biggrin:
I figure I got my moneys worth and it was an interesting jaunt
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Glad to know I wasn't the only one bingeing today. :l2:
Looks like we spent about the same, but I think you did better.
Lots of heavy metal in your pile, and a boatload of do-dads to go with it.
Very nice! :icon_biggrin:
Since the Holidays are coming up, I hope my music store guy can move a few bedroom amps for me. :dontknow:
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went to visit an old friend today. picked up a NOS thordarson 22r36 PT - 1200VCT @ 200mA couldn't resist for 20 bux. i have NO idea what i'm going to do with it. maybe class AB with x-mitter tube?
also picked up a webster electic SP-3 for 5 bux.
the original 7189 is gassed out so he sold me a NOS IEC for 10 bux. when i got it home i opened it up and noticed that the OT primary lead to main filter cap was burned in two. still measures ~190R but i have reservations. also, one of the cement power resistors crumbled. it has 3 12AU7, 1 6DJ8, 1 7189, and 1 6CA4. rear panel states 5W output. PT measures good.
like this one... (http://www.ebay.com/itm/Webster-Electric-Type-SP-3-Amplifier-/291617396331?) i'm thinking tweed princeton
--pete
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1200VCT @ 200mA , brings to mind choke input allow a wide variety of heft power tubes.
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This one looks in rough shape but for $23 and whatever time and parts it needs to be fixed, it could be a little bedroom amp easily. Ends in 6 hours, and I'm out of ammo again.
http://www.ebay.com/itm/371485587181?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/371485587181?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
Do your own research before spending your money. Careful, this junk gear can be addicting. :l2:
OK, nobody wanted to take the shot I guess.
Even in it's rough shape it should have had a useable PT, OT, and some still good tubes.
The Silvertone R-R I got just needed a new cap can and it was a Champ 600 with a tube PS. It sounds really good with an external speaker connected now.
If I wasn't out of ammo, for $23 including shipping, I would have taken that shot. :l2:
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1200VCT @ 200mA , brings to mind choke input allow a wide variety of heft power tubes.
it does that and a lot of added weight. :icon_biggrin: 5Hy @ 500mA is not inexpensive or light weight. very likely i'll flip it on fleabay.
--pete
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You take your shots and live with the results.
Someone already got to the Miniwatts I was hoping were still in here. :sad2:
I'll have to try to find the full schematic for this online, and see if I'm better off sticking some tubes in it to fix for resale or just harvesting the parts.
It does have a PT (labelled 250mA) and maybe an OT that could be used.
Gutted and re-engineered it could fit a 6" speaker in for another unique little bedroom amp.
I need to find a schematic before I get too crazy with this.
It's a Norelco EL3951 if you have an idea where to find a schemo. I'm going searching now.
It might be worth more to someone else if I fix it then a bedroom amp would be. :dontknow:
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You take your shots and live with the results.
Someone already got to the Miniwatts I was hoping were still in here. :sad2:
I'll have to try to find the full schematic for this online, and see if I'm better off sticking some tubes in it to fix for resale or just harvesting the parts.
It does have a PT (labelled 250mA) and maybe an OT that could be used.
Gutted and re-engineered it could fit a 6" speaker in for another unique little bedroom amp.
I need to find a schematic before I get too crazy with this.
It's a Norelco EL3951 if you have an idea where to find a schemo. I'm going searching now.
It might be worth more to someone else if I fix it then a bedroom amp would be. :dontknow:
Here is a link to info on your unit.
http://www.radiomuseum.org/r/philips_el3581_50r.html?language_id=2 (http://www.radiomuseum.org/r/philips_el3581_50r.html?language_id=2)
You will need to join the radio museum to get the schematic, but this will let you see it.
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Thank you Ed!
The Philips support person got me a link for a Hi-Fi web site that had a schemo in German for that model you listed.
The 3951 doesn't seem to be out there anywhere, yet.
That model seems close enough in that it has only two tubes, 1 9 pin and 1 7 pin.
The schemo did not identify the tubes though. 9 pin shows heater pins 4,5 and 9, I'm thinking that means 12AX7.
Appears the 7 pin is the output tube and I'm thinking that means 6AQ5.
I sure wish those MiniWatts had been in there. With just those two premium tubes I would have considered this a good deal!
Now I'll have to really work to try to make it into one.
All part of the adventure though. :laugh:
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That model seems close enough in that it has only two tubes, 1 9 pin and 1 7 pin.
The schemo did not identify the tubes though. 9 pin shows heater pins 4,5 and 9, I'm thinking that means 12AX7.
Appears the 7 pin is the output tube and I'm thinking that means 6AQ5.
ECC83/12AX7 and EL95 (http://www.mif.pg.gda.pl/homepages/frank/sheets/030/e/EL95.pdf). See below from the RadioMuseum website Ed linked.
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Thank you HBP!
My Army network isn't allowing me to go to that site.
It's odd which sites it will and won't allow. At least this one works. :icon_biggrin:
So I guessed the 12AX7 correctly, but an EL95/6DL5 wasn't on my radar.
I'll have to check my tube supply. I don't know that I have that one.
Thanks for the help guys! :worthy1:
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Reading some threads on another site about low output problem with EL95 PP setup.
Seemed to indicate he did a direct swap with 6AQ5s and got full output power.
I haven't checked the tube data sheets for these tubes yet, but do any of you know if you can just swap a 6AQ5 in for an EL95/6DL5? :dontknow:
I've got lots of 6AQ5s. :icon_biggrin:
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I've added a poll to give me a better idea of people's interest in this topic.
With my obvious response already tallied. :l2:
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I have never seen such a minimalist tape player with speaker and record.
It is, as-expected, largely a Champ with far too much added switching (much omitted here).
There's certainly no 250mA in the B+. You may have found the relay supply.
That is a 6P2T relay; you can't hardly buy one today. Before you bulldoze, find out what the coil voltage is.
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No plans to bulldoze, yet.
That EL95/6DL5 does not seem to be very common. I don't have any of those in stock.
Lots of 6AQ5s, a 6CU5 and a 6EH5 which look similar, but not a 6DL5 in sight.
This thing looks pretty clean inside, and I see others like it being offered at $100+ on Ebay.
I can put a 12AX7 in, was hoping it was a 6AQ5 to put back in, test and verify it's working and put in back out there with a starting bid that nets me a small profit.
I don't know if that's feasible now. You say there is a hard to come by relay in there?
Here's a pic of the PT. I'm guessing the 250mA is total for the PT?
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Checked the data sheets. Pinouts are exactly the same.
Differences noted:
AQ uses more than 2x heater current 450mA vs 200mA.
With just two tubes in this, heater current should not be an issue?
Max Plate dissipation DL = 6W, AQ = 10W
Plate current DL = 24mA, AQ = 45mA
Load Resistance DL = 10K, AQ = 5K
Max output power DL = 3W, AQ = 4.5W
Please tell me if my analysis of this data is wrong.
I guess that as long as the PS can supply the extra heater and plate current, a direct swap is OK?
The Load resistance through the OT needs to be 1/2 as much for the AQ.
So connecting a 4 ohm speaker to an 8 ohm output jack would work for the AQ swap?
Anything else I should be concerned about?
Any reason I should not just stick a 6AQ5 in with a 12AX7 and test this thing?
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Thanks Ed!
That is a better schemo than I got through Philips. It labels the tubes and gives some voltage readings.
Any feedback on me subbing in a 6AQ5 for the 6DL5? :dontknow:
I don't think it would destroy anything, but I could be wrong if it exceeds the heater current available from the PT.
It is about 250mA more current required than if I had a 6DL5 to put in there.
I got the rest of my weekend junk gear purchases delivered today.
Cleaning them up, and will likely post a pic or two after work tonight. :icon_biggrin:
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Thanks Ed!
That is a better schemo than I got through Philips. It labels the tubes and gives some voltage readings.
Any feedback on me subbing in a 6AQ5 for the 6DL5? :dontknow:
I don't think it would destroy anything, but I could be wrong if it exceeds the heater current available from the PT.
It is about 250mA more current required than if I had a 6DL5 to put in there.
I got the rest of my weekend junk gear purchases delivered today.
Cleaning them up, and will likely post a pic or two after work tonight. :icon_biggrin:
I would simply plan for the tube you prefer within reason. Most Transformers will exceed expectations. If it heats up too much a heater tranny to me is cheap enough to let me build what I want.
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These are the major parts resulting from my $50 purchase last weekend.
Based only on these quality parts alone, not the other pots, caps, power resistors, etc. , I consider this to have been a good deal. :icon_biggrin:
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That large tranny has a lot of 6.3 supply. it is a 115v at 290-0-290 which is a nice unit to have. You can build anything from 15 watts to 40. Looks perfect for a Vibroverb.
Do you know what the Philco Trannys came out of or did you find the specs on them? You have collected some parts, but have you built anything yet?
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That large tranny has a lot of 6.3 supply. it is a 115v at 290-0-290 which is a nice unit to have. You can build anything from 15 watts to 40. Looks perfect for a Vibroverb.
Do you know what the Philco Trannys came out of or did you find the specs on them? You have collected some parts, but have you built anything yet?
10 A on three separate 6.3 VAC taps can heat up a lot of tubes. :icon_biggrin:
Found a Philco radio site with pretty much info. My parts appear to have been a 32 model? The site didn't have specs for my stuff of course. Still searching.
Of course I have built some things by now. My problem has been a lack of proper OTs and speaker cabs.
I have one PP and one SE OT. It appears I have two more SE OTs now, at around 5W I'm guessing.
I use the 2x12 cab from my pawnshop Peavey Mace as my testing speakers now.
I have a 6V6 PP with 6SJ7 pre and 6SN7 PI that was using my only PP OT.
I end up tearing out the OT from things I have built when I want to try something else. :BangHead:
That chassis and tubes came out of a Magnavox with a Field Coil Speaker.
The PT in it went bad, so I used my bench supply. I have a few PTs that could go in it now. I don't think I want to use this one in it.
That sounds like a project for this weekend. I need to figure out which PT to use, wire up my 5 rectifier tube, and field coil socket connection.
I could reclaim my one PP OT for a little while at least. I am interested in how that monster field coil speaker will sound in a guitar amp.
It's at least 12" and might be 15", I didn't measure it. I was a little leery of running the HV out and back into the amp through that old wiring and unknown speaker.
It's got to be done, so I guess that's what I'll focus on this weekend.
I have a couple of SE EL84 projects that were kind of on hold because I didn't want to play swap the OT on them.
I'm hoping these two new (old) Philco OTs will fit the bill for them. I could keep my one new SE multi-tap OT for my breadboard projects then.
It would be a whole lot easier to just buy a complete kit from Doug! More expensive, but nice and clean to work on, and a prettier product in the end.
I don't think I could sell one of those at a profit. :dontknow: I'm not really looking to build and sell amps though.
I'm trying to learn, and work through the more difficult challenges presented when repurposing old gear into an amp. :BangHead:
I'm just looking to sell a couple of these repurposed things now, to keep the steady flow of cheap, high quality part containing, junk gear running through my basement.
I guess you could call it a hobby. :l2:
Added a pic of the rest of the high quality parts harvested from this buy. Not necessary to try to value any of this stuff, as the PT alone is worth more than $50 IMO.
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If I didn't mention it before, I reco looking on your local Craigslist for old oscilloscopes. For one...you might get a functional scope if you do have a latter-20th century one. They have to be CHEAP because there are *some* parts that are useful but a lot that ARE NOT.
Power transformer: In a big scope, you'll have as many as 1/2 dozen 6.3 windings. But the B+ ampacity is generally inadequate for amp use. That's because either there are 3 B+ windings and they divide up total device current on 3 diff windings. Or the thing uses 30-50 mils total. So not one of them is really strong current-wise. So scope transformers are usually really big (heavy, take up lots of chassis footprint) and yet not so great for an amp. In a nice Tek scope, you may well get a 12AX7 or two but most of those 9-pin tubes are 6DJ8s (which are much like 12AX7 with a different base pinout) You will get lots of good hardware from a junked Tek tube scope. Knobs.
A little 1957-1962 3" offbrand scope will furnish an astoundingly small pile of usable parts. KNIGHT kit scopes, however, use 12AX7. Very old Dumont scopes used 12AX7. MOST other scopes use 12AU7 or 6DJ8 and these are tubes you can add to your collection and impress your friends but generally will not use.
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Irresistable 2 for $10 deal. 2 Blonder-Tongue line video amps. Nice chassis with cages and princeton sized 350-0-350 tranny. 6BQ5 will not fit under the cages but 6V6 will. Pretty clean.
(http://i172.photobucket.com/albums/w32/ttm4/blonder_100_zpsmwpexru3.png) (http://s172.photobucket.com/user/ttm4/media/blonder_100_zpsmwpexru3.png.html)
(http://i172.photobucket.com/albums/w32/ttm4/blonder_200_zpsunukerfa.png) (http://s172.photobucket.com/user/ttm4/media/blonder_200_zpsunukerfa.png.html)
These would be neat for a dual mono block 6V6-fired stereo. Or brown Princeton or Deluxe. I of course need a project like that. I thought the chassis were inspiring. And duallys!
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Wow, a very nice find, in stereo. :worthy1:
Where did you get them?
A slightly bigger cage would be easy enough to make, or just put the cage on stilts. Those PTs will give you a B+ big enough for 6L6s if that's what you wanted to put in there.
:worthy1:
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Test equipment is a good source of parts. A great place to find inexpensive gear is at Hamfests. In the US, check out http://www.arrl.org/hamfests. (http://www.arrl.org/hamfests.)
A HP 200CD signal generator provides a chassis and a lot useful parts. Remove and rearrange a few things, add an output transformer and you have a nice little amp. The manual has some nice chassis shots: 200cd - Bama Boatanchor Manuals Archive - Edebris.com (https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwj7vuzgnKzJAhWBHD4KHQ-ICqIQFggcMAA&url=http%3A%2F%2Fbama.edebris.com%2Fmanuals%2Fhp%2F200cd%2F&usg=AFQjCNGk8UE3DPaG4xEDfnHqQawUFAMCqw). As a bonus, the older models came with a 5AR4 rectifier tube. Well worth the $25 that I've bought these for.
Another find is a Tektronix 310A scope. It opens like a book to reveal an amazingly packaged piece of gear. Lots of tubes. High quality parts.
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Thanks for your input xm52!
Broken or unknown test gear has been probably my best source of high-quality parts for cheap.
Competition is slight and prices very reasonable, if you don't mind getting dirty cleaning them up. :laugh:
Many people say these are not good candidates for conversion into a guitar amplifier,
but in my mind parts are parts, and high-quality parts for cheap are hard to come by.
Most say converting different audio equipment is the way to go. Like Bogens.
I'm gonna let this one slide by as it's more amp than I want or need. Maybe it is something one of you louder fellows might be interested in.
http://www.ebay.com/itm/221936022519 (http://www.ebay.com/itm/221936022519)
I just got a super clean Bogen K10, and a B&H Filmosound 302 15 watt.
These are more in my desired power output range, and should need very little modification to be rocking guitar amps.
I've got one more item coming into range, and will post that if I take the shot.
That Bogen listed above might be a decent platform for someone interested building a PP 6L6 40-50 Watt output guitar amp. :dontknow:
That is a lot more output than I need. Do your own research to see if that Bogen might meet your needs.
There is documentation available online for free for that specific model. :icon_biggrin:
Somebody wants 5x what I paid for my B&H without a speaker. :icon_biggrin:
And he might actually get it... :dontknow:
Another with a more realistic BIN price of 2x + of my cost.
More confirmation for my mind that I got a good deal. :icon_biggrin:
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Paul I'm beginning to think you might be an emoti-con artist. :icon_biggrin:
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Paul I'm beginning to think you might be an emoti-con artist. :icon_biggrin:
An interesting play on words/symbols there. :l2:
The BIN price on that Bogen is definitely a better deal than this one that just sold on my watch list.
Over $100 including shipping for a Magnavox stereo dual SE EL84s with one channel distorted??? :w2:
The way I value items, I'm hard pressed to see over $100 in parts in that.
I like deals where my conservative value of parts is at least 2x the total price I paid.
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This one is out of my price range, but it is BIN, free shipping and premium tubes!
http://www.ebay.com/itm/Roberts-440-Tube-Stereo-Amplifier-Project-EL84-12AX7-Telefunken-Free-Shipping/391329039518?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D34225%26meid%3D5b6a3442b7f444cebc6bd83c16d0c183%26pid%3D100005%26rk%3D1%26rkt%3D3%26sd%3D151895410007 (http://www.ebay.com/itm/Roberts-440-Tube-Stereo-Amplifier-Project-EL84-12AX7-Telefunken-Free-Shipping/391329039518?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D34225%26meid%3D5b6a3442b7f444cebc6bd83c16d0c183%26pid%3D100005%26rk%3D1%26rkt%3D3%26sd%3D151895410007)
In parts, I can see at least the BIN price in this one. Maybe not 2x, you be the judge.
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In parts, I can see at least the BIN price in this one. Maybe not 2x, you be the judge.
You don't buy that one for parts... you buy it because you're gonna add your own preamp(s) to turn it into a usable amplifier.
That is a power supply chassis which already has 2x EL84 single-ended output sections, complete with a 1/2 12AX7 driver, and output transformers off-chassis. All that needs is a preamp for your signal to drive the output section that's already assembled for you (which originally powered the Left & Right speakers for that tape machine).
The smart money figures out how to take what's existing and go the extra-mile to make it suitable for your use. It is less-sensible to rip it apart, then find you have 5 miles to go to put it back together the way it was (because the parts yielded work best the way they were originally assembled), and then go the extra-mile to make it suitable for your use.
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In parts, I can see at least the BIN price in this one. Maybe not 2x, you be the judge.
You don't buy that one for parts... you buy it because you're gonna add your own preamp(s) to turn it into a usable amplifier.
That is a power supply chassis which already has 2x EL84 single-ended output sections, complete with a 1/2 12AX7 driver, and output transformers off-chassis. All that needs is a preamp for your signal to drive the output section that's already assembled for you (which originally powered the Left & Right speakers for that tape machine).
The smart money figures out how to take what's existing and go the extra-mile to make it suitable for your use. It is less-sensible to rip it apart, then find you have 5 miles to go to put it back together the way it was (because the parts yielded work best the way they were originally assembled), and then go the extra-mile to make it suitable for your use.
I agree with that 100%. :icon_biggrin:
That one looked perfect, as you pointed out. :worthy1:
I was just saying that the parts alone, even if one had to go 5 miles extra, looked to be worth the price on this.
If I had an extra $150 to drop, it would already be mine. :sad2:
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Making a usable amplifier. As you can see my most recent purchases are definitely moving in this direction. :icon_biggrin:
I'm learning.
I'm still of the opinion that, if you can get high quality parts cheap enough,
it is often worth it to go that extra 5 miles. :BangHead:
The K10 came in today. Definitely one more suited to modification into a rockin guitar amp.
Major score on the tubes! I got a Mullard 12AX7, and a Bugleboy EZ80! :happy1:
I have stacks of 6AU6s (with 2 Mullards in the bunch) and nearly as many 6AQ5s (no premiums here, but plenty that test above NOS specs).
Overall she's very clean. I won't get filthy getting it prepared for modification.
Got the tubes out, DeoxIt sprayed in sockets and pots.
Even if I have to change all the caps in this, I should have it rockin before the end of the weekend. :icon_biggrin:
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Over the weekend I had a thought.
It may not be especially applicable to tube GUITAR amps. But it would be pretty darn good for building a stereo tube amp with minimum fuss.
Triode Electronics sells "upgrade/rebuild" kits for Dynaco Stereo 35's and 70's. These boards handle everything surrounding the little tubes.
You can buy a naked dual channel preamp PC board from them that uses your choice of 6AU6, 12AX7, 6DJ8 (6922) or any of half a dozen other tubes. Naked board just under $40, with parts (you have to build) for $85. A little high but the sourcing is all done. They have a whole section devoted to Dynaco stuff. They are obviously afficianados. I found it interesting that they have a version that uses 6AU6, a tube you get in large qtys with junk gear but is otherwise semi-useless.
It is true that I could build such a circuit for under $85, but I was thinking the naked PC board is well worth the $40 just to get the thing built in a known, proven, short-lead-length, good documentation supplied kind of way.
The boards are meant to install from the bottom, necessitating a big rectangular cutout on the main chassis. But I see no reason why they could not mount on 4 short standoffs above the main chassis. Poof, instant stereo amp from a carcass.
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Cleaning and inspection done.
Only one area with two things noted.
Someone's been in here and did a repair/modification.
1st E cap has some bulging corrosion. It's got to go before I apply power.
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> 6AU6, a tube you get in large qtys with junk gear but is otherwise semi-useless.
6AU6 is a hopped-up mini of the 6J7, *the* all-purpose pentode which nearly all sharp-cutoff pentodes are derived from.
FWIW, the BBC made a whole location mixer with 6AU6. Preamps were wired triode using *screen* as anode, and the nominal plate as a grounded shield. Then 6AU6 pentode gain-stage, and 6AU6 triodes for driving a phone line.
6AU6 can generally be used for small-signal pentodes. Adjust the G2 resistor to get plate voltage ratio similar to what you are adapting from.
It is also a fair approximation of a half a 12AU7 lo-gain triode.
It was not aimed for low-microphonic quality. However many of the types once sold for low-crackle have been picked-over and abused so much over time that a "right type" is no assurance either. If 6AU6 are flooding your bench, you can select for low-microphonics. The shakier ones can be strong cathodynes or even puny "power" amplifiers.
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6136 & 7543 are subs for 6AU6 - sylvania claims 7543 are low microphonic, low hum, and high rel.
--pete
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Thanks, PRR. I certainly recall that for the 40+ years I have been messing around with tube junk, 6AU6 are plentiful and I really had no need for them back then, either.
I am thinking, in the context of ordering and using one of the Triode Elect boards, I should get one for 6AU6 and even if none of 20 or so I have are non-microphonic, then NOS ones can probably be bought for $3-4 instead of "whatever the market will bear" for 12AX7.
For the moment and for building a stereo tube amp out of a dual-6BQ5 carcass of some kind (bot one for $5 at the last junkfest and I probably have 2-3 others) these PC boards make a lot of sense and are worth trying.
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I was hoping to pick up a similar Bogen for cheap tonight.
That doesn't look like its going to happen now.
They've already driven the price half way to crazytown, I can see that's where they're headed.
I'm out now. :l2:
The clown car to crazytown must have broke down. :l2:
The price ended here. Not a terrible deal. I should have bid a couple dollars more at the end. :dontknow:
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Hey this is a great thing, I also been searching for some deals, and found this one:
Don't mind the language just look at the pics !! :icon_biggrin:
http://sp.olx.com.br/sao-paulo-e-regiao/antiguidades/valvulas-antigas-de-televisao-25462214 (http://sp.olx.com.br/sao-paulo-e-regiao/antiguidades/valvulas-antigas-de-televisao-25462214)
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I gave you guys a shot at this one last week. I couldn't let it slide by again.
It looks like a little piece of shit, unless you know what it's got hiding inside. :icon_biggrin:
I call it the SwollenSack by 3M cause it's stuffed with a good tube amp inside.
I'm familiar with these because my Dad worked for 3M and I used one of these as a kid.
These have a 10W PP tube amp inside. I remember them being pretty loud on just the internal speaker.
For less than $25 for a complete PP 10W tube amp you can't go wrong!
Cheaper than you will find a comparable B&H amp. Most just don't realize what these have inside. :icon_biggrin:
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I got 28(one inside the box, 27 in the pic with all of them) tubes from that deal!! There are some I have no clue what they are but there is like 2 6v6 one is GT, 2 tubes that looks like double triode, 5Y3 is a rectifier yes? 50L6 there is like 2, 2 or more 35Z5GT !! :icon_biggrin:
Got pics !
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Greetings Uki,
Thanks for sharing your experiences with us. The point is to learn from each other on this thread.
So with that said, this is my take on buying junk tube lots.
You really have to be careful and know your stuff here. Better yet, you know the seller and know what type of lots he sells.
You have to get a screaming deal most times for these to work out. I have posted some of my tube lot buys.
Mine have averaged less than $0.25 per tube delivered right to my door.
I have found one seller in particular that I trust to buy from.
He packs them properly so none arrive crushed, other seller's haven't and I got some crushed tubes.
I have a tube tester so I can check these untested lots. His lots always contain over 85% good used tubes.
OK, but have you seen a pile of used tubes pulled from old gear before? Many are filthy.
Covered with decades of smokey, oily, grime, and dust that smells funny.
So, I usually spend an hour or two unwrapping and wiping down the tubes with a rag and hot soapy water.
Ohhh, guess what, That writing stencilled on the tube will usually wipe right off then. So you should ID the tube before cleaning.
I then take a permanent Sharpie marker and write the ID on the tube.
So now you have a bunch of clean and marked tubes, great, but are any of them any good for guitar amps?
Usually not. You definitely are not going to get a box of used Mullard 12AX7s for $25.
Most easily identified guitar tubes are going to be removed from their lots before they sell them.
Guitar tubes go for significantly more than other tubes. Sellers know this.
I have had a couple Mullard and Bugleboy guitar type tubes slip by into the lots I bought, though.
That's what you are hoping for, one Mullard or Bugleboy can pay for the whole lot.
If you are going to try to resell them (I never do) you need to be careful not to wipe off the markings.
Mostly you are going to get a bunch of obsolete TV or Radio tubes that no one else wants to buy.
Hopefully, you got a few usable guitar type tubes from your lot.
It's a lot of work for mostly junk, but I did get a few premium Mullard and Bugleboy guitar tubes this way.
That's my perspective on junk tube lots. :dontknow:
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Good hints!
I got luck on this one , those 2 9 pins pre-amp tubes, are sweet velvet sound like, tested them and then put one at a time in the amp, then I put both in the amp, I got like a new amp now !!
Also i got:
1x 6V6 GT
1x 6K6 GT
1x 5Y3 GT
1x 6AQ5A
Here is the pics of those 2 9pins ones:
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I think you got a vintage 12AX7 and maybe a 12AT7 in the deal!
It's amazing how a premium tube can change the sound of your amp.
I am glad you are happy with your purchase! :icon_biggrin:
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Somebody picked up that Telefunken listing. I thought it might go quickly.
Was it one of you lurkers. Please let us know if you got it and how it works out.
The BIN Bogen is still available, for somebody interested in a 40-50 Watt platform.
Or this auction that ends in 4 1/2 days for a PP 6L6 Bogen minus tubes.
http://www.ebay.com/itm/172012831370?euid=5f0c907f9906457ca0b682c8fff322ce&aid=222007&meid=f211ed23b9bd4f63bdaa2219d976a955&cp=1&_trksid=p11010.c100352.m3747&_trkparms=aid=222007&algo=SIC.MBE&ao=1&asc=20150112095601&meid=f211ed23b9bd4f63bdaa2219d976a955&pid=100352&rk=11&rkt=12&sd=291625056642 (http://www.ebay.com/itm/172012831370?euid=5f0c907f9906457ca0b682c8fff322ce&aid=222007&meid=f211ed23b9bd4f63bdaa2219d976a955&cp=1&_trksid=p11010.c100352.m3747&_trkparms=aid=222007&algo=SIC.MBE&ao=1&asc=20150112095601&meid=f211ed23b9bd4f63bdaa2219d976a955&pid=100352&rk=11&rkt=12&sd=291625056642)
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If you have a unidentified tube often you can bring the numbers back long enough to read them by putting the tube in the freezer for a few hours, then carefully looking it over at an angle in relatively bright light quickly after removing from the freezer.
There are some basic guidelines from construction too.
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If you have a unidentified tube often you can bring the numbers back long enough to read them by putting the tube in the freezer for a few hours, then carefully looking it over at an angle in relatively bright light quickly after removing from the freezer.
There are some basic guidelines from construction too.
Excellent tip Ed! :worthy1:
From the construction of those two, are you able to identify them positively?
Uki told me one had more gain than the other, and I'm pretty sure the long plate one is the velvety smooth sounding 12AX7. :dontknow:
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From the construction of those two, are you able to identify them positively?
No, other than that they are a 12A_7 type. To determine which type for certain, I'd stick them in a preamp and measure plate output with a known sine wave input to the grid. I'd also do the same with a known 12AX7 to get a quick baseline for actual gain in the circuit used. Separately, 12AX7 and 12AU7 often have similar construction features; though not always, 12AT7 usually has very-different plate construction compared to 12AU7/12AX7.
What can be seen from construction is they are a "Philips-family" brand tube, which would include Mullard, Amperex, etc., but also Matsushita Japan (who built a factory with old Philips machines & Philips know-how, if I have the story straight). There are several indicators that these are from a Philips company, but the most-obvious is the X-shaped seam at the top of the tube envelope.
... I'm pretty sure the long plate one is the velvety smooth sounding ...
Be careful generalizing based on the plate length; all you know for sure from that is the long-plate should be more prone to microphonics. The shorter-plate 12A_7's is a later development to shorten the construction so that it's more rigid, and less prone to microphonics.
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You guys are a wealth of knowledge. Thank you for sharing!
I wasn't aware the long plates were more prone to microphonics.
I did notice some Ebay sellers touting the long plates on some premium tube listings.
Uki had 1 other Philips tube in this lot, PY something. I think it turned out to be a rectifier.
One of those 12A_7 tubes clearly had a double layer base holding the plates together.
I'm happy that Uki got some premium Philips (MiniWatt?/Mullard/Amperex) tubes in this deal.
He seems very happy with the way these tubes improved the sound of his Korean made EL84 amp.
I just checked my MiniWatts/Bugleboy/Amperex tubes and all have the Philips X marks the spot top.
Some but not all the Mullards had the X. I take it those are vintage production and not the reissue type.
More valuable premium tube identifying information shared. Thanks! :icon_biggrin:
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I can tell certain construction techniques, but I am much more familiar with companies construction. The Matsushita tube brand HBP mentioned is a good find and nice sounding tube generally.
I prefer RCA tubes mostly and while I am a fan of Telefunken Smooth plate 12Ax7 for audio. In small tubes EL84 I pay the bux for Amperex as they do not distort as harsh. That is why I run plate voltage close to 300VDC or less on them cause I want them to last.
I do like EI's and have grown to like RCA "pan" getter.
Also, I am a tung-sol freak and like every one of theirs especially the 6V6. I just put a matched set in a 5G9 head and used it this weekend playing and I have to say the transition from clean into distortion is hardly even noticeable. Very musical and still keeps a openness to chords and I was playing a ES335 Travis style. Have to say I was impressed.
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You guys are a wealth of knowledge. Thank you for sharing!
I wasn't aware the long plates were more prone to microphonics.
I did notice some Ebay sellers touting the long plates on some premium tube listings.
Uki had 1 other Philips tube in this lot, PY something. I think it turned out to be a rectifier.
One of those 12A_7 tubes clearly had a double layer base holding the plates together.
I'm happy that Uki got some premium Philips (MiniWatt?/Mullard/Amperex) tubes in this deal.
He seems very happy with the way these tubes improved the sound of his Korean made EL84 amp.
I just checked my MiniWatts/Bugleboy/Amperex tubes and all have the Philips X marks the spot top.
Some but not all the Mullards had the X. I take it those are vintage production and not the reissue type.
More valuable premium tube identifying information shared. Thanks! :icon_biggrin:
PY82
Here is the full list(or almost):
35Z3 - 5x
BSA6 (not sure about this)
6AQ5A - 1x
6SA7 - 2x
6BA6 - 2x
6SQ7 GT - 1x
7A8 - 1x
12AT6 - 1x
12AV6 - 1x
12BH7 A - 1x
12SK7 GT- 1x
25L6 GT - 1x
25BQ6 GT- 1x
50L6 GT - 3x
PY82 - 1x
6K6 GT - 1x
6V6 GT - 1x
5Y3 GT - 1x
12___ - 2x
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I took a shot at some premium tubes. $56.77 including shipping for 100 Euro tubes.
As long as they are not all duds, I should come out ahead on this:
http://www.ebay.com/itm/100pc-Euro-Tubes-Mullard-Amperex-Philips-Brimar-Telefunken-Siemens-Valvo-/151899460817?_trksid=p2047675.l2557&ssPageName=STRK%3AMEBIDX%3AIT&nma=true&si=LztFkZLUeQr5FYrG0fWMaW3iHM8%253D&orig_cvip=true&rt=nc (http://www.ebay.com/itm/100pc-Euro-Tubes-Mullard-Amperex-Philips-Brimar-Telefunken-Siemens-Valvo-/151899460817?_trksid=p2047675.l2557&ssPageName=STRK%3AMEBIDX%3AIT&nma=true&si=LztFkZLUeQr5FYrG0fWMaW3iHM8%253D&orig_cvip=true&rt=nc)
I could see at least 1 Mullard 12AX7 a number of Mullard 6AU6s and I'm hoping one of the Octals is an EL34, I don't have any of those.
I only need a few good ones from this to break even. :dontknow:
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OK, no big whiney fest here, but I did get the EURO tubes today.
You take your shots and learn to live with the results.
What I thought was a 12AX7 turned out to be another of those 7247s.
Got a few Mullard 6AU6s and what else?
Like about 8 magic eye indicators, how many of those does one need?
Lots of shiny silver Holland tubes to add to my collection of who knows what these are good for. :dontknow:
Not a 12AX,AU,AT7 in the bunch. No 6BQ/AQ5s, and of course no big power tubes like EL34/6L6.
When you buy from a frequent tube seller this is about what to expect.
They know what is good and sells for big money, and will sift that out for sure.
Some sellers do have tons of old pulls that they don't want to bother going through, keep an eye on these guys.
People who sell junk gear usually have no idea if the tubes in their gear are valuable or not.
This continues to be my best source of used premium tubes. :icon_biggrin:
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Not a 12AX,AU,AT7 in the bunch. No 6BQ/AQ5s, and of course no big power tubes like EL34/6L6.
When you buy from a frequent tube seller this is about what to expect.
You gotta be careful about getting caught up in excitement on ebay. If the seller doesn't catalog what they're selling, you should assume there's nothing but t.v. tubes in the lot (unless you see something you're sure is desirable; even then you likely don't know it isn't dead).
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Not a 12AX,AU,AT7 in the bunch. No 6BQ/AQ5s, and of course no big power tubes like EL34/6L6.
When you buy from a frequent tube seller this is about what to expect.
You gotta be careful about getting caught up in excitement on ebay. If the seller doesn't catalog what they're selling, you should assume there's nothing but t.v. tubes in the lot (unless you see something you're sure is desirable; even then you likely don't know it isn't dead).
I know, just illustrating my adventures. :think1:
What's a good used Mullard 12AX7 worth $30-$40, Mullard 6AU6s maybe $10. So I could see close to my price including shipping if just these tubes were good.
Lot's of upside potential with 90+ more tubes to go through.
I had never bought from this seller before, probably won't again.
I should have known when he wrote "Lots of money to be made by sorting through these".
That there was more likely little or no money to be made.
I did get a couple of EL91s and EL95s in there. I can use one of those for my little Norelco R-R instead of the 6AQ5 I subbed in.
I haven't sorted and researched all that I got in this lot yet. I'm considering it a break even deal at this point. No major score here.
Back to watching for junk industrial/military gear that can be had for less than $50 including shipping.
Amazing how often that stuff has premium tubes and other high quality parts in it. :icon_biggrin:
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About 4 hours left on this one. I know they look like little POS, but there is a complete 10W tube amp in there. :think1:
http://www.ebay.com/itm/141847571950?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/141847571950?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
It's less than $35 including shipping to my location. I can't get a new 10W PP OT shipping included for that.
I'm out of ammo again. Got an Oscope, signal tracer, and HP pulse generator on the way now. :icon_biggrin:
If this POS is working it doesn't need any modification to be a guitar amp. Plug your guitar in the mic jack, a better speaker on the output and you're rock-n-rolling. :icon_biggrin:
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You know, if you are really a junk hound (and believe me, I have been for most of my life and sometimes do and sometimes don't acquire junk) you should check out your local Craigslist. There are some rudimentary search tools on CL.
The thing about a CL sale is:
search for tektronix, hewlett "ham radio" "oscilloscope". (There are millions of scopes for sale. Don't overpay for a junky old tube scope, there are really not a lot of usable parts. Old Dumonts use more 12AX7s than other scopes but sheesh, they are 50 years old now.
obviously no shipping charges
little better idea of what you are buying
that other thing or twelve sitting in the corner
that box of wires thrown into the deal
I would posit right here and now, you could find a tube Conn organ for free or for $25 that would be equivalent to about 6 of your current deals. The issue is can you move the thing. Or a Lowrey. Or a Wurlitzer. I don't really like to break apart Hammonds even if they are stupid organs like the S-6.
*Schober* organs are chock full of 12AX7. Gold mine. Most other organs are full of 12AU7.
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I have an ad up for old junk gear on CL. I also check for deals once every 2 weeks or so.
Problem is Louisville is a 1 hour drive each way.
Minimally valuing my time and fuel means I have $50 into going to get something for free.
In light of that, the Ebay purchases I make don't seem so bad. :icon_biggrin:
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Here's a free scope.
(http://i172.photobucket.com/albums/w32/ttm4/tek_561_zpsdji3r273.png) (http://s172.photobucket.com/user/ttm4/media/tek_561_zpsdji3r273.png.html)
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Junk test gear comes through again! :happy1:
I know most of you think I'm crazy buying this kind of stuff. :l2:
HP 214A Pulse generator. Got to love the junk HP gear.
26 tubes total in this thing. I knew from the manual it had 3 12AX7s.
Most of the tubes in this were Amperex Euro (Gt. Brittain/Holland/Germany) tubes.
So 3 vintage Amperex 12AX7 tubes more than covers my cost on this. :icon_biggrin:
I knew that going into the deal.
Pleasantly surprised to see that Amperex 6DJ8s go for $15 a piece. I got 9 of them. :icon_biggrin:
Even if I sell them at a discount of $10 a piece I will have doubled my money and got my 12AX7s for free.
The 2 7534 tubes should easily bring in another $25. Still more tubes included, but I'll stop here.
Then the high quality PT, pots, switches, resistors, etc. are just icing on the cake.
I'm thinking this one just paid for my newly acquired used Oscope and Signal tracer. :icon_biggrin:
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What ?!?! 26 tubes, plus components, and more more for just 20 bucks !!! :laugh:
That is a good deal no doubt !!!
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Well almost $46 including shipping, but:
Parts are parts, and Premium Quality HP parts for cheap are hard to beat! :icon_biggrin:
Sometimes the sum of the parts is greater than the whole.
That is a rather unusual PT, with 3 separate HV sections.
Another rarely seen part was an AC input noise filter.
That might be useful if you used a gas AC generator at an outdoor event. :dontknow:
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Pretty nice!
One has to wonder if it's possible to make an adapter so that 6DJ8's could be used for 12AX7. (answer = yes) Just have to fiddle with the filament, all the other pins are the same. Sell 'em or use 'em, the value of the piece is mostly in the tubes...and the knobs.
When I looked up the manual for that piece I noticed that (at least the one version I found) the printing date was 1975. That seemed a little odd, for hp to have had tube *anything* hanging around, eg, still in the catalog in 1975. Probably part of it is, they were gov't approved and their stuff would sell for 3+ years after they discontinued it because of the way the gov't bids things.
You'll generally find the transformers to be a little odd in hp gear. The thing to note in test gear is that the power supplies are not built to handle big excursions of power like audio amps are. What this means in practical terms is that the tranny might very well supply say 275 volts post rectifier because that's all a pulse generator that (surprisingly) can make a 100 volt pulse needs. Just saying, I have generally found salvaged hp transformers to be kind of problematical because they won't make 350 volts. OK, voltage doubler. Now you come out of the rectifier with close to 600 volts.
OK, so it would be a great tranny for....say a reverb unit. Or say a 6G2 Princeton. Except it's a big fat tranny that's way oversized for a reverb unit. Most hp PT = problem child.
I am only telling you this to relay my experience (tho I have never taken apart a 214A) that the PT voltages from test gear are very often goofy for amp use, not in any way to criticize your scrap hunt. If you can make out on the tubes, go ahead, it's pretty cheap entertainment. The other remarkably high quality parts......you'll seldom use.
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One has to wonder if it's possible to make an adapter so that 6DJ8's could be used for 12AX7. (answer = yes) Just have to fiddle with the filament, all the other pins are the same. Sell 'em or use 'em, the value of the piece is mostly in the tubes...and the knobs.
When I looked up the manual for that piece I noticed that (at least the one version I found) the printing date was 1975. That seemed a little odd, for hp to have had tube *anything* hanging around, eg, still in the catalog in 1975. Probably part of it is, they were gov't approved and their stuff would sell for 3+ years after they discontinued it because of the way the gov't bids things.
You'll generally find the transformers to be a little odd in hp gear. The thing to note in test gear is that the power supplies are not built to handle big excursions of power like audio amps are. What this means in practical terms is that the tranny might very well supply say 275 volts post rectifier because that's all a pulse generator that (surprisingly) can make a 100 volt pulse needs. Just saying, I have generally found salvaged hp transformers to be kind of problematical because they won't make 350 volts. OK, voltage doubler. Now you come out of the rectifier with close to 600 volts.
OK, so it would be a great tranny for....say a reverb unit. Or say a 6G2 Princeton. Except it's a big fat tranny that's way oversized for a reverb unit. Most hp PT = problem child.
I am only telling you this to relay my experience (tho I have never taken apart a 214A) that the PT voltages from test gear are very often goofy for amp use, not in any way to criticize your scrap hunt. If you can make out on the tubes, go ahead, it's pretty cheap entertainment. The other remarkably high quality parts......you'll seldom use.
Like a toroidial input/output transformer. :laugh:
You made me run to the 6DJ8s data sheet. OK, so it's not quite a 12AX7 sub. Amplification factor only 33 not 100, but do they also have a sweet sounding output?
Of course, the 12AX7s are actually 12AX7WAs which I had to look up too. Interesting heater upgrade circuit for Mil application/specifications. All 3 tested low on my tester, but remarkably balanced and consistent. I no longer concern myself with the testers readings, especially when they are balanced and consistent across tubes like these. So the real test is to put them in an amp and listen. Well, these 3 are right on par with my Mullard or Bugleboy. :icon_biggrin:
Most people don't consider knobs, but this type with 2 allen screw locks are great! Also, the pots are on a completely different level from most other guitar amp/consumer type gear pots.
I might have to try a few breadboard prototype circuits replacing 12AX7s with 6DJ8s before I decide whether to sell them or not. :think1:
I don't think I will need/use the 4 big tubes, but now will need to closely check the data sheets and forums before just listing them on Ebay. :sad2: :w2:
Thanks :l2:
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> odd, for hp to have had tube *anything* hanging around
This was bleeding-edge in 1963. 13 NANO-seconds rise/fall?
It was many years before transistors could touch it for speed.
It was decades before transistors could touch it for 100V(!!) output with such speed. It also peaks at 2 Amps. The output stage is a bit more like a transmitter than a plain signal generator. Those are rather unusual output tubes.
Meanwhile it musta got wrote-into many test specifications. If you wanted the contract to calibrate radar SL-987 or nuclear counter XYZ-123, you had to have a "HP 214A or equivalent". And I bet there was no exact equivalent. So buyers would pay HP's price. Being a proven product, HP would be unlikely to re-design until they saw a way to make it 10 times better. They did have slower weaker and much smaller transistor pulse generators. Probably a long time before they beat this combination of size, SPEED, and POWER.
Both the output tubes and the known-genuine 6DJ8 are valuable. Please don't "sub for 12AX7". Don't even handle them. Hi-Fi nuts are crazy for them. 6DJ8 is "just a TV tuner tube", but the best of the bunch, meaning all the genuine ones are long-gone and every dang bottle with the same pinout has been re-badged "6DJ8", no matter how unlike a true 6DJ8 it is. The re-marks have given 6DJ8 somewhat of a bad name (because so many 6DJ8 preamps 'sound' like a low-price TV tuner, because that's what's been stuck in them). But true 6DJ8 fans will cream to get bottles you document to have come out of unmolested 1970 HP gear.
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But true 6DJ8 fans will cream to get bottles you document to have come out of unmolested 1970 HP gear.
Once again you come through with the inside scoop on all things tubes!
Thank you very much PRR!!! :worthy1:
I did notice some of them were the gold pin type.
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The ckt for that hp 214A definitely has some interesting aspects. Tubes with -75 volts on the plates? Hey, no problem, there's -275 on the cathodes, LOL.
You're right PRR, that piece had some pretty impressive specs even 30+ years after it came out. And yes, the output tubes are very unusual.
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me> I bet there was no exact equivalent.
CMC Ruthrford model B7B Pulse Generator (http://www.bunkerofdoom.com/lit/rutherford/index.html) seems to be remarkably similar, but lower-cost. TV H-sweep tubes instead of the exotic EL130.
Company still in business (unlike HP Test).
http://www.itsamerica.com/Files/history.htm (http://www.itsamerica.com/Files/history.htm)
"The Story of the Radar Range Simulator" 2/3 way down page
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Company still in business (unlike HP Test).
thought they became agilent after HP spun them off on their own, then they were bought outright.
--pete
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reply 187 -
pics with the power transformer: looks like it has a resonance winding [ 50/1KC ]. so part of a ferroresonant regulated supply?
--pete
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> there's -275 on the cathodes, LOL.
There's no possible transformer for these pulses. (One use is revealing the faults of the best available pulse transformers.) So the load is a choke, made with coaxial lines. For safety this needs to be at zero V DC. As you say, no problem, take the cathodes way negative.
The ITS/Rutherford site says the Navy was buying stuff like this well into the 1980s, buying parts at least until 2002. And concerned that it be an exact equivalent to the originals.
> thought they became agilent
Well, yeah. I'm still disgusted they dropped the H-P name, let the PC division have it. Rolls Royce Jets was kind enough to license the R-R name and badge to VW or BMW or whoever bought the dregs of the car spinoff.
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I'm still disgusted they dropped the H-P name
me too. they could have kept the name as long as they only made test equipment under the name: certainly that wouldn't have caused any issues. damn sue happy legal buzzards.
:sad:
--pete
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I'm still disgusted they dropped the H-P name
me too. they could have kept the name as long as they only made test equipment under the name: certainly that wouldn't have caused any issues. damn sue happy legal buzzards.
:sad:
--pete
I think the computer division has actually destroyed the Good HP name.
I have said I used to say HP stood for High Priced, but it also stood for the best scientific test equipment money could buy.
Their gear was very expensive, but the only brand you knew you could trust.
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Well after the favorable 6DJ8 feedback I got here from you very knowledgeable guys,
I decided to give another HP 214A a go. I had to pay a little more this time, but still should profit nicely.
I might have found a funding source for my other junk gear purchases. :laugh:
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Is there a good reason to take that apart if 98% of the value is in the tubes that just yank out?
You should probably buy more 214A's, put the glunky tubes you get in them, and relist them. Move them units, LOL.
I once bot a $10 Tek scope that was loaded with 6DJ8s but 3/4 of them tested very weak.
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It appears there is not much interest in HP 214As. :l2:
They are quite old. The 1st one had most of it's cap cans sitting on broken insulators.
It is quite easy to just pull the tubes though. I couldn't get to 1 6DJ8s without removing the big clunky switch.
Once I get to tearing things apart, I guess I just get a little carried away. :l2:
I will probably not strip this one naked like the last one.
The chassis does seem to be a decent platform for a rack mounted guitar amp.
Did the low testing 6DJ8s not sound good? My 12AX7WAs tested low but sounded just as good as my Mullard or Bugleboy.
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I have no piece of audio gear that uses 6DJ8s and you are correct, they are more or less 12AU7s which are sub-useful, gainwise. I just one day found myself with a dozen or so 6DJ8 and decided to test them all on my (now ill) Hickock 600. So I have no way to report on audio performance. I think I had 6-8 6DJ8 that were 30-40% = very sketchy. *And* uneven. The stinkers were real stinkers.
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My tester is a Heathkit TC-1 which even using the TC-2 tube listings doesn't show tester settings for most of the tubes in the 214A. :w2:
It does list settings for 12AX7s. My 3 tubes tested remarkably balanced. 5 readings were like 39, 6th reading 40.
My other 12AX7s test closer to 50, but when I put the WAs in my K10, they all sounded great.
You wouldn't happen to know where I can get settings for more tubes for my tester would you?
If not, I'm thinking of just listing some of these with returns accepted.
Let the buyer try them out and if not completely satisfied just pay to ship them back for a full refund. :icon_biggrin:
I'm pretty confident in the quality of the parts HP used in this gear. :icon_biggrin:
I found a better settings list for my tester. It had settings for 6922/6DJ8/ECC88.
I had 12 tubes, from PQ Amperex 6922 with gold pins to Sylvania 6DJ8s.
All tubes tested well balanced, and the range was only 38-42 for all 12.
Most tested 40/40, worst 38/40, best 40/42. Pretty sure this means all are good to go. :icon_biggrin:
Still can't find tester settings for the PQ 7534s.
Data sheet shows those are powerful audio tubes.
The pair is capable of 60W output!
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Only selling 2 tubes from my hockey puck analyzer has netted me a profit and lots of free high quality parts.
Maybe I should just focus on scavenging parts to resell at a profit and use those profits to buy pre-made amps. :l2:
Naah, I am actually enjoying myself rekindling my old electronics training learning more about guitar tube amps. :icon_biggrin:
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Another HP 214A? Really :w2:
After selling off a few tubes to net my costs,
Free high quality used HP parts can't be beat!
It does take some work, but it is worth it to me. :icon_biggrin:
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Are some of you lurkers starting to bid on HP 214A's? :w2:
Up to this point I was usually the only bidder on these items. :l2:
I couldn't blame you if you are, the 214A does have an impressive lineup of tubes and assorted parts. :icon_biggrin:
But it is definitely not a guitar amp in disguise.
Some people think they can still get a lot of money for these. I don't see that happening.
I just wait for them to get tired of relisting their item and finally price it to go. :l2:
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Any feedback on my latest purchase?
Hammond big iron on sale. :icon_biggrin:
Here's what I make of this item.
1 beefy PT.
2 PP 20+W OTs for EL84 or 6V6 amps.
1 PP 30+W OT for 6L6 or some kind of Bass amp OT? :dontknow:
The questionable OT is being driven by 2 7591s at +400V to an 8 ohm speaker.
It is labeled Bass amp and has 130 ohm coils on each side of the CT.
7591 data sheet shows 6.6K plate load at 400V for 32W output.
Any idea if this is OK for 2 6L6s?
If not, any suggestions for what it might be used with it besides the 7591s?
I saw 6GM5s listed as a 9 pin equivalent of the 7591. I don't think I have any of those either.
I'll have to double check my tube inventory. LOL
PS.
I think the seller has 1 more of these available at the BIN price of $29.95 :think1:
With my sale he sold 3 of these in the last 24 hours. They are going fast. :icon_biggrin:
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> Hammond big iron on sale.
Just so you know: I think Hammond Organs and Hammond Transformers are totally different companies.
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Here's what I make of this item.
1 beefy PT.
2 PP 20+W OTs for EL84 or 6V6 amps.
1 PP 30+W OT for 6L6 or some kind of Bass amp OT? :dontknow:
Stereo.
The EL84 OT's are for left & right of the stereo spectrum. I've not had one of these amps but I'll venture a guess these OT's are small for their power through-put. That's because there's no low end for either the left or right channel being passed through them... That's been shaved off by the 3 C-R (high-pass) filters between the input jack and the 7199 pentode driver of the output stage.
The bass for both left & right channels is passed through 3 R-C (low-pass) filters between the input jacks and the 7591 channel's pentode driver. The bass-only sound is amplified and applied to a much bigger OT for connection to the woofer. This works because bass is generally omnidirectional, which is why stereo mixes evolved to sitting the bass right in the middle of the stereo picture... If you have any deep lows, it doesn't convincingly sound like it's coming from only the left or right speaker (and also why you have a single subwoofer speaker in a modern stereo setup).
Any feedback on my latest purchase?
It would seem a shame just to rip it apart. You never wanted to hear your tunes through a tube stereo? All you need are the speakers, tubes and a check that electrolytic caps are still good... Then verify you have or can make all needed power supply voltages.
7591 data sheet shows 6.6K plate load at 400V for 32W output.
Any idea if this is OK for 2 6L6s?
7591 is a 19w 6L6 in a 6V6-sized bottle, with a much-twitchy-er gas pedal. Has ~70-80% higher Gm, so it take less drive signal and bias to make its output power as compared to the 19w 6L6.
7591's used to be $75-80 a bottle; now there's new production as cheap as ~$18/bottle. Or you could ebay them & find some on occasion for less. Switching to 6L6 means bias supply re-design and possibly an added gain stage or changed/redesigned inverter to give them sufficient drive to produce low end to match the EL84 channels. Buying some 7591's is the shorter path to joy.
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My first inclination when looking at this was to keep it all together as a stereo amp, but then I considered not having all the necessary tubes and a speaker cab with the 3 speakers, so I then evaluated just the transformers instead. I concluded that the transformers alone were worth considerably more than I had to pay, so I pulled the trigger. :l2:
I have a need for at least two EL84 PP OTs for my current stock of premium tubes.
I don't want to kill any more little unknown wattage OTs, and only have 1 PP OT I'd like to reserve for my breadboard set up.
I don't think that OT could handle 2 6L6s, so the Bass amp OT seemed like it might be a bonus item.
I have at least two extra PTs in stock that would easily work with the EL84s.
I hoped I could use this beefy PT and unknown OT to make a PP 6L6 amp.
I did read something about this particular Hammond model having some failure issues.
Is this really a shame to part this out to make 3 amps instead of 1? :w2:
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> Hammond big iron on sale.
Just so you know: I think Hammond Organs and Hammond Transformers are totally different companies.
Yes, I think you are correct about that and everything else you post about tube gear! :worthy1:
Hammond Organs did use quality transformers that were designed and matched well with their output tube circuits, correct?
With so many people converting Hammond Organs into guitar amps, I'm guessing these transformers work well for that?
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There is no PT on the AO-70 chassis.
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> Hammond big iron on sale.
Just so you know: I think Hammond Organs and Hammond Transformers are totally different companies.
Yes, I think you are correct about that and everything else you post about tube gear! :worthy1:
Hammond Organs did use quality transformers that were designed and matched well with their output tube circuits, correct?
With so many people converting Hammond Organs into guitar amps, I'm guessing these transformers work well for that?
Usually you will find Inductor (Choke) inputs on organs and organ cabs. This will give you a voltage multiplier of .08 to 9. Also it makes for much smoother DC and will make for a very different Guitar amp. If you are looking to build a very clean Guitar amp this is a good way to go.
I have one which I used 12Ax7 to a 12aU7 PI and 4, 6v6 tubes from a JR20 Tone cab. Hooked up to a Hepner 12 AlNico sounds very much like a Standel.
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There is no PT on the AO-70 chassis.
Really? I see four transformers.
Three OTs and a Choke then?
Then the big black one is for the 7591s?
I think you are correct in that PS components are labeled 7xx and power amp 3xx.
I'm having a hard time locating that (choke) on the power amp schematic.
It's all good. I happen to have an excess of PTs at this time.
So I have a PT for each proposed amp already in stock. :icon_biggrin:
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There is no PT on the AO-70 chassis.
You are correct, Sir. :worthy1:
This shows a more complete setup, and that really is a beefy PT. :laugh:
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So, if I have a 7199 for V305 I'm thinking I can check channel A's amp by:
Lifting C329, attaching input jack to R350 + C330.
Use my Bench PS to provide the +310, +300, and +275 to the circuit.
Attach 8 ohm speaker to channel A output, and strum away. :icon_biggrin:
Similiar setup for channel B. :think1:
If I had some 7591s, I could check bass amp by:
Lifting R406, attaching input jack to C364 + C365.
Use my Bench PS to provide the +400, +350, and +305 to the circuit, with -24V attached to the bias circuit.
Attach 8 ohm speaker to bass channel output, and strum away. :icon_biggrin:
If that all worked it might be rather simple to chop this up into 3 amps. :think1:
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The choke is not on that partial schematic you posted. The choke is the plate load for the reverb driver. There's a lot of other stuff on the chassis that's missing from your partial schematic. You can find a complete schematic by searching for Hammond H100.
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So far my Google searches have only come up with a zip file that has those schematic segments.
I did look at each page, but I guess I missed that choke. That is OK.
That one segment contains the important power amp info I needed.
I am hoping that choke will also be adequate for a low amperage PS design. :dontknow:
The main parts I wanted were the two EL84 PP OTs. The rest is icing on the cake. :icon_biggrin:
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This is on the same page as the partial schematic you posted. I used that same choke on my Plexi6V6. There's still a lot more stuff on that AO-70 chassis that's not shown on your schematic. And a lot of the stuff that's on your schematic ain't on that chassis. But if all you want is the iron, it really doesn't matter. A tube set for that chassis would be expensive. And that still doesn't have a power supply.
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Great! and thank you.
The choke goes in the +1 column, and it appears the bigger black OT will work for a pair of 6L6s. +2 :icon_biggrin:
I think I will try to test the EL84 circuits as outlined above, if I can find a 7199 in my tube inventory.
I am interested to see how that single 7199 tube pentode/triode configuration sounds as a guitar amp.
Maybe it just needs a 12AX7 with tone stack added to the front of this circuit to be more guitar friendly? :dontknow:
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Another HP 214A? Really :w2:
After selling off a few tubes to net my costs,
Free high quality used HP parts can't be beat!
It does take some work, but it is worth it to me. :icon_biggrin:
Well the HP 214A came through for me again.
It was loaded almost exclusively with HP labeled Amperex tubes made in Holland this time. :icon_biggrin:
Selling off just the 9 6DJ8s should net me nearly double my costs.
Everything else are free parts then, including the 3 HP labeled Amperex made in Holland 12AX7 tubes.
The cheapest listing for I could find for one of those was BIN at $57 including shipping. :icon_biggrin:
About the PQ 7534s otherwise known as E130Ls, does anyone know of an audio amp circuit for these?
I have been searching for one, but so far have come up empty handed.
They are 10,000 hour audio tubes capable of 60W output for a pair.
The Ebay market won't pay me half as much for one of these as it will for a 12AX7.
So with 4 of these PQs and the other 2 being Mullards I'd like to find a design to use them in.
It could be a stereo Hi-Fi design if that is the best use for them.
I can't see listing these tubes multiple times just to get $15 a piece for them.
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Back to the Hammond now.
No wonder all the tubes were pulled from this.
The 7199 is out of production, 7591s are very expensive, EF86 same, only EL84s are still reasonably available.
I don't have any 7199s, but have read the 6GH8 and 6AN8 are subs with the proper pin reassignments.
I have at least 1 6GH8 and a few 6AN8s. It seems some HiFi'ers prefer the 6GH8 over the 6AN8 as a sub.
All seem to say to pay the price for the 7199s if you can still get them, as they sound much better than the subs. :dontknow:
Now it seems the only economically feasible use of this Hammond is to chop it up and redesign for more readily available parts.
Would any of you experienced members think it is worth my efforts to sub in the 6GH8 to test the EL84 circuits as they are? :help:
I'll end up chopping up these EL84 circuits anyway because I don't have enough subs for the 7199s.
I'm pretty good at tearing things apart, putting them back together is another story. :l2:
I'll be going to a more standard 12AX7, 12AT7, 12AU7 well-known preamp design.
At least, these tubes are widely available at reasonable prices.
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I guess when it rains it pours. :icon_biggrin:
Poor seller should have set a reserve or higher opening bid. :w2:
I hope he doesn't try to cancel the sale. :cussing:
Obviously two different Hammond PP OTs.
This should satisfy my lower wattage PP OT needs for a while.
Unless, of course, I can get more of these for less than $4 a piece including shipping. :l2:
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No complaints from the seller and marked as shipped. :happy1:
For only $.01 I might have had compassion on this poor seller and let him out of the deal if he had :sad2: enough.
He will definitely get positive 5 star feedback from me! :icon_biggrin:
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Decided to pick up a 7199, since I got it for less than a 12AX7.
Much easier to just plug this in than try to pin swap for a sub.
I definitely will try the EL84 circuits as they are before any disassembly now.
I am very interested in how they sound. Clean with lots of headroom, is cool.
Adding a pedal or two to the input is an easy way to get the sound you want, in that case.
Much easier than redesigning the circuit to get that sound, IMO.
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Hi guys, Still a lot of great old stuff out there.
Never thought I'd see another one (or two)of these.
(http://i761.photobucket.com/albums/xx254/Timbo-08/009%203_1.jpg) (http://s761.photobucket.com/user/Timbo-08/media/009%203_1.jpg.html)
(http://i761.photobucket.com/albums/xx254/Timbo-08/010%202_1.jpg) (http://s761.photobucket.com/user/Timbo-08/media/010%202_1.jpg.html)
(http://i761.photobucket.com/albums/xx254/Timbo-08/007%202_8.jpg) (http://s761.photobucket.com/user/Timbo-08/media/007%202_8.jpg.html)
These old "PYE" TV's were in just about every home in Australia and as a lad (around 1968)spent my share of time holding the spiral antenna trying to get some sort of watchable picture. We had four stations with one of these you could only get if you lived on top of a hill.
Lots of mustards, but not the usual guitar type. Good PT. Small OT, couple of watts. Decent choke. Another transformer that is marked as "VERTICAL OUTPUT TRANSFORMER" don't know if it is useable.
I can see where the local amp builders got there tubes.
6CM5
6BL8
6DX8
6BM8
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Nice!
The best thing about something like that is people will sometimes just give it to you.
They know that a TV like that is not worth fixing.
Bogen has some PAs that use the 6BM8.
I think the 6CM5 can also be used as an output tube. :dontknow:
The little OT will work with it's current output tube.
If your vertical output transformer is like the one I have it is 1:1.5 windings.
Maybe useable in a reverb/tremolo circuit? :dontknow:
No Marshal stack conversions here, but many parts for a simple bedroom amp. :icon_biggrin:
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> "VERTICAL OUTPUT TRANSFORMER" don't know if it is useable.
A V-sweep circuit "is" an audio power amplifier. It has to cover 50Hz-5KHz so the picture looks OK, and typically does a bit better; half to several Watts depending on the CRT size.
Main question is the output impedance. Sweep yoke impedances didn't come standardized like speakers; often the yoke, V-sweep, and H-sweep parts were made and sold as sets. Measure turns ratio. That paper tells what tube is the V-sweep output. See if the impedance into available speakers works out anywhere near reasonable.
There's obviously a speaker amplifier on there, but I don't see the tube type.
"6CM5" is better known as EL36. Also EL6 (diff base) and PL36 (diff heater).
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Hey PRR, The small sound output transformer was connected to the 6DX8 and applying 9.6v to the primary gave me a Z of 3600. I don't know what the speaker ohms was but with an 8ohm load would work with the 6DX8, 6BM8 ......
I was looking to use these small transformers for reverb drivers with tanks that have 8ohm inputs.
The VOT has a few wires attached.
Blue orange and red have continuity with 121ohms between red and orange and 397ohms between orange and blue.
Applying 9.6v to blue and orange as these were connected to pins 7 and 6. The only reading I get is on the short black and orange of 1.4v.
Going off the tube chart the 6BM8 is the vertical output tube.
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My Hammond organ chassis and the other OT order came in.
I actually got 3 OTs for $.01 in that deal. :icon_biggrin:
I'm waiting for the 7199 I ordered to come in to test the 2 EL84 circuits as the are.
The guts of it look clean, no obvious burnt or removed parts.
I'm gonna pull the big black OT, test it manually, and then find a simple PP 6L6 circuit to try on my breadboard. :icon_biggrin:
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How about a simple mod project?
Says it's a working 12AX7 driving 2 EL84s PP OT for I'm guessing 12-15 Watts output power, AM/FM tuner amplifier.
A simple modification to the Phono or Aux jack input should turn it into an AM/FM tuner / guitar amplifier. :w2:
For less than $40 including shipping I have a hard time making myself not buy these items. :help:
More of my items will need to get listed on Ebay before this weekend, to more equally balance the flow of funds before my wife gets mad. :cussing:
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Selling a pair of tubes that covers the last purchase should keep the :cussing: to a minimum. :icon_biggrin:
Buying good deals and selling items at a considerable profit keeps my junk gear enterprise rolling along.
Building a nice inventory of cheap/free high quality used parts to use in my projects.
I still need to make some profits to spend on some tools.
Drill press/bits, saws and other wood working items. :w2:
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How about a simple mod project?
Says it's a working 12AX7 driving 2 EL84s PP OT for I'm guessing 12-15 Watts output power, AM/FM tuner amplifier.
A simple modification to the Phono or Aux jack input should turn it into an AM/FM tuner / guitar amplifier. :w2:
For less than $40 including shipping I have a hard time making myself not buy these items. :help:
Well, the AM/FM tuner appears to be out of alignment, but I didn't buy it for that anyway.
The PP EL84 output section works very well. :icon_biggrin:
No major hum or other problems noted.
The Bass and Treble pots seem to have a nice effect on the tone.
I used 2 adapters, 1 stereo to RCA and the other to convert to 1/4" plug.
When I come in through the tape port, the signal goes through a 6AU6 to the 12AX7 to the EL84s.
Very similar to the Bogen K10, with what seems to be a better tone stack and a little more output from the 6BQ5s compared to the 6AQ5s.
The seller had listed his tube tester results for all the tubes in this.
The 6BQ5s appeared to be significantly mismatched, so I swapped in a closely matched pair of Channel Masters from one of my other junk gear purchases.
Sounded pretty darn good like that, but swapping the 12AX7 for one of my premium tubes made it sound even better.
Next I need to find one of my Mullard 6AU6s to swap in. :icon_biggrin:
It has a switch for internal and external speakers, or external only.
It didn't come with an internal speaker, and it appears to like the external speakers as 2 x 12 at 4 ohms over 1 x 12 at 8 ohms.
With some preamp line and gain boost added into the tape input she really shines, for a low watt amp.
With the boost and internal volume dimed she sounds great, with a nice sounding easily controllable feedback available by pointing the guitar at the speakers. :icon_biggrin:
Now for my dilemma on what to do with her. :think1:
I could purchase the Photofacts service manual/schematic for this.
It is Montgomery Wards Airline Model WG-2661A, if any of you have access to that schemo and wouldn't mind sharing it with me. :worthy1:
I would appreciate that greatly, otherwise my searches so far have come up empty and I'll need to purchase it.
I'm pretty sure I could follow the service manual instructions to re-align the AM/FM tuner.
It's been about 25 years since I have done that type of thing, but I do have experience with this type of procedure.
The question is "Is it worth it?" Do you think someone would pay more for a low watt guitar amp with a built in AM/FM tuner?
Otherwise it would be simple enough to:
Change tape input to 1/4" jack
Make a speaker cab to mount this in
Mount a 1 x 12" speaker I already have
Remove the tuning dials/display and pot
Remove function switch, leaving On/Bass Treble and Volume pots out front
Guitar input and speaker output jack with internal/external or external only speaker switch would be on the side of the amp
I think just mounting this in a decent cab with a 1 x 12" speaker would make this a $250+ value amp.
I'm not sure anyone would be willing to pay significantly more for an aligned AM/FM tuner with switchable functions on a home guitar amp. :dontknow:
What do you guys think?
Just make a guitar amp, or get the service manual and make all the features function properly again? :w2:
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The Hammond PR-40 Tone Cabinet is a treasure trove of speakers, vintage hook up wire, tubes, transformers, cab parts and all kind of miscellaneous parts. I've had two. It had three EL84 push pull amps in it. One I got for free and the other I paid $20.00 for. Believe it or not, one I made an interface for and used it for a guitar practice amp for a couple of years--big practice amp. After I finish having my way with them, parted them out. I'm presently selling the last of the parts on e-bay including the interface I made. One or the PT's and choke is going on my present Plexi project. Platefire
BTW- Here is a pix of the interface I made to hook my guitar up to the PR-40. It's made out of an old battery charger and supplies fused AC power to the PR-40 and power switch to turn it on and off plus preamp input jacks that goes G1 and G2 Grids all through a 5 pin female connector to the Pr-40's Power Supply chassis.
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It really wasn't a difficult decision on what to do with the Airliner.
With todays technology someone could just use an adapter to connect their Ipod or smartphone to play their tunes or radio on it if they really wanted.
Actual value perceived added by realigning tuner = 0. Cost of Photofacts is > 0. Realignment procedure is a NO GO. :laugh:
Have any of you considered adding an Audrino card to your tube amplifier circuits.
That could add Bluetooth connectivity and possibly signal processing effects if designed properly. :think1:
This thing actually sounds really good. The bass and treble pots can have a dramatic effect on the quality of the sound output.
I currently have this hooked up to my computer for listening to music and Youtube videos.
Listening to a talk show, you can really improve the quality of the audio with these tone controls.
Even when the recording qualities are poor you can adjust the tone to closely match how you know that persons voice sounds.
With a guitar, just a little level/gain boost is needed on the input to really rock out. :icon_biggrin:
This one is a little cleaner and louder than the K10. The K10 doesn't need any boost on the input to rock out.
I've got the Airliner currently driving 3 Peavey 12" guitar speakers, and it sounds rather impressive for a bedroom amp.
I am quite pleased with this Airliner! Now to spend some time designing and constructing a decent cab for it.
A single 12" speaker will be what goes in the cab with it. :icon_biggrin:
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I guess I needed to climb up on a hilltop to really see all the territory I've gained. :w2:
A picture is worth a 1000 words, see below. :laugh:
Looking over my captured territory, I need to see if I have the proper wells for my houses, and where the outhouse's need to be placed to not contaminate any of the wells.
This all makes much more sense if you are hip to PRR's house plumbing analogy for guitar amps. :worthy1:
I really don't need to gain any more territory until I have completed building some houses with the proper plumbing. :l2:
The Bogen K10 and the Airliner are both working fine, and will be kept as test bench reference amps.
The circuits for these are quite similar except for the output section.
It looks like I may already have most of the parts I need to make two more of each of these.
The other two are much different. A simple 12AX7/6AQ5 SE output conversion.
On the other, I'd like to use that Hammond organ chassis as my platform for a 6L6 PP output circuit.
I'm not really sure what to go with on that, and am strongly leaning towards buying a turret board from Doug on this one.
I'd like to try at least once to make a nice cleanly laid out amp that looks as good inside as it sounds outside.
If I could learn to build them as nice and clean as mscaggs, I might think I'd have died and gone to Heaven. :laugh:
I need some metal and woodworking tools to really make good progress .
The crappy SS 10W conversion works as it is now, but those tools would allow me to finish it up right.
I checked a local Pawn shop for things like a table saw, a drill press with good bits and some clamps and other junk amp housings and speakers.
Maybe when I get paid I can try to get a package deal on those items, and anything else that is needed to help me fully finish a few amps. :laugh:
It's one thing for me to have an open amp sitting next to me on my bench to play when I want.
It's another thing completely, for me to sell an amp like that on Ebay to some young and dumb guitar head
that might have little children running around. I've got to encase those potentially lethal voltages in something before I can sell it with a clear conscience.
Behold, a portion of the territory I've captured is displayed below. :l2:
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Timbo, was the 6DX8 used for SE power amp stage?
I found a nice radiogram with a chassis just for power supply and stereo 6DX8 PP - that chassis converted very nicely. A control panel strip also provided a 12AX7 and 6N8.
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Hey Tim, Yeah the 6DX8 was the sound output and the 6BM8 for the vertical output.
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Ok, so it would be a single ended output stage. Interestingly the recommended SE and PP stage output transformer loading are both about 16kohm. Could make yourself a nice midget 1-1.5W bedroom amp!
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It's not like I really need another project to work on. :BangHead:
I just cannot pass up what I know to be a good deal on Ebay.
So, for $60.07 delivered I picked up a "working" Wurlitzer Model 7011 organ amp.
Here's what the seller had to say about it:
This is a vintage Wurlitzer 7011 amplifier out of a model 4602 organ.
This amplifier was working when it was removed last year from the organ.
This amp has 2 6L6 tubes, 1 5U4G, 3 6SN7GT, 1 6SL7GT, 2 6SQ7.
I paid $40 for a new pair of Peavey 6L6GCs before.
With a 5U4G and 1 6SL7GT that should pretty much assure I got my $60 worth in tubes alone. :icon_biggrin:
I don't have any 6SL7s and am interested to hear how they sound after hearing many good reports about them.
If it proves to be in working condition, it should not be too big of a project to convert it into a guitar amp.
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The guy you bought the AO-70 from now has the matching power supply listed...
http://www.ebay.com/itm/Vintage-Hammond-H100-Series-Organ-Power-Supply-/121872907690?hash=item1c6030fdaa:g:kuEAAOSwLnlWonkc (http://www.ebay.com/itm/Vintage-Hammond-H100-Series-Organ-Power-Supply-/121872907690?hash=item1c6030fdaa:g:kuEAAOSwLnlWonkc)
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Thanks
It might have been useful to me if I was actually making an organ. :l2:
I've got the thing stripped. I've made a Hoffman Stout with one of the OTs on my BB.
Almost ready to put that in a real chassis now.
And I just finished making a Wards Airline design PP 6L6 amp on my BB with the bigger OT.
It's working but I'm not sure this is the design I want to build in a chassis yet.
I've got another similar PP schematic that is negative voltage grid biased I may have to try. :dontknow:
Luckily I've got a few PTs from my other junk buys that will work for the 6L6s.
This one is really big iron and expensive to ship.
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Well I did it again. :l2:
I didn't need another project but for $63.15 delivered how can I pass this up. :dontknow:
4 Vintage 6V6GT tubes, and what looks like 2 5U4 tube rectifiers to me.
Just those tubes pretty well justifies my purchase price. :icon_biggrin:
My K10 might sell locally for $200 this week.
And I hope to have a bare chassis Hoffman Stout ready to go by this weekend. :icon_biggrin:
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And again? :w2:
A Bugleboy rectifier tube, a 12AX7 that looks like it has the premium X on top, 1 blown 6BM8 and 1 good?, a PT, OT, a reverb tank, and free shipping for $60???
Done!
I think I have at least one or two of those 6BM8s in my tube stash.
I'm praying some of my amps start selling soon, Please God?
I do get the pay after delivery which gives me another two weeks before I really have to pay. :w2: :l2:
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This was quite an excellent score at the local e-waste place. $40.
Entirely unmolested Voycall model 25KR PA amp. Original, clean, with cage with just some minor chassis gloin, little tranny rust. All RCA tubes, RCA 6SJ7 *2 and two RCA Blackplate 6L6GC! Prelim research says the amp wants a 5V4 versus the 5U4 that is in there. S'OK. As yet untested. Just got it home in exactly this condition. Very cool.
I was a bit hesitant but when I turned it around and saw those RCA 6L6's there was nothing further to think about.
One wonders: The front panel with the tone controls and the metal plates with the legends, that looks 30's-40's. Looks pretty cool, too. Indeed, the stencil around the 6L6 tubes says "6L6G". So why am I finding 30-40's front panel styling; 6SJ7 tubes (late 40's-50's) and yet 6L6GC? Probably all the tubes were replaced in this with RCA's shotgun style sometime in the mid-60's.
(http://i172.photobucket.com/albums/w32/ttm4/voycall_3_zps9edwhqgk.png) (http://s172.photobucket.com/user/ttm4/media/voycall_3_zps9edwhqgk.png.html)
(http://i172.photobucket.com/albums/w32/ttm4/voycall_4_zpsovacfgeh.jpg) (http://s172.photobucket.com/user/ttm4/media/voycall_4_zpsovacfgeh.jpg.html)
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Indeed, a very nice score! :worthy1:
Those 6L6s were probably replaced at some time.
My 6L6Gs are a different shape from the GB/GCs it appears you have in there.
If it is older, then it was probably built with 6L6Gs.
These have the same specs as the metal 6L6 as far as I can tell, and can't take the higher voltages of the newer ones.
If your plate voltage is like +380 or a little less than even the metal 6L6s can go in there. :icon_biggrin:
Really nice score! A few simple mods into a Rocking guitar head, and I'd guess it would be worth at least $300 to someone.
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Yeah, you can see the metal 6SJ7s and 6L6's in this example. Not pretty! http://www.radiomuseum.org/r/voycall_amplifier_25dr.html (http://www.radiomuseum.org/r/voycall_amplifier_25dr.html)
Yes, 6L6G's are bowling pin shape; they can be large or small. I have a pile of NOS JAN Sylvania 6L6G. The 6L6GCs are worth as much or more than the amp to fetshists. Untested. My Hickock tester is on the fritz.
Other than bring it up slowly on a variac, I have to decide what to do with this. I will replace the 5U4 with a 5Y3 to get a 2 amp rectifier instead of a 3 amp one in there and keep the B+ lowish while I test it out. Fortunately electronics has a way of waiting patiently. It's really pretty clean, I don't want to ravage it. OTOH, it's not like a '57 Strat.
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Yes, the metal tubes look rather industrial. :dontknow:
But in a circuit designed for the 6L6G,
I cannot hear any difference in the metal, Gs, or GCs. :icon_biggrin:
The metal ones are significantly cheaper to replace. :l2:
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You're actually making the same very good point I think I made to you; on general principles, it's better to do whatever I'm gonna do to this with old but good 6L6Gs I have lying around instead of the GC's. Just in case something blows and takes out a tube. I even have metal ones.
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Free Lowrey organ. There are about 10 12AX7A across the the top, all seemed to be RCA so far. The two broad rows of tubes are types I have never even heard of, 6KM8, 6FH8. Four plate tetrodes. Sure. And 6X8's, I've heard of those. The power amp is 2-3x 12AX7 and four Syl 7591s. Not a bad tube haul.
Sometimes I go hot and cold on junk. lately, hot.
(http://i172.photobucket.com/albums/w32/ttm4/org_9_zpsp2akoa3x.png) (http://s172.photobucket.com/user/ttm4/media/org_9_zpsp2akoa3x.png.html)
(http://i172.photobucket.com/albums/w32/ttm4/org_8_zpso5wxmkps.png) (http://s172.photobucket.com/user/ttm4/media/org_8_zpso5wxmkps.png.html)
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A "Vovcall" apparently sold in Japan:
http://fat-guitar-stock.jimdo.com/amplifier/vovcall-50-s-microphone-amp/ (http://fat-guitar-stock.jimdo.com/amplifier/vovcall-50-s-microphone-amp/)
Robot translation:
It is the 1950s of the microphone amplifier.
In the United States, by modifying the 1950s of the microphone amplifier has it is done well to use as for the guitar.
It is a microphone amplifier, but also the performer of many blues harp thing also moderate drive can be obtained with good uses a microphone amplifier of this age.
Jack input and output for use as for guitar are exchanging.
6v6 × 3
12AU7 × 1
6AU6 × 1
12AX7 × 1
Drive sound like tweed period can be obtained and will raise the volume.
The output contributes to a about 10 ~ 15w.
Because it is originally microphone amplifier high-pass is mild sound, please use the guitar of a single coil.
Impedance 8 Ohm
Left of the knob volume
The right of the knob is treble
Second from the right is based
It does not use the second and third from the left.
117V specifications
Amplifier body is slightly microphonic but, especially problem is I think that there is no need to the volume to the full 10.
"3 X 6V6" must be wrong.
I can believe early 1950s by a small builder using-up 1940s escutcheons.
There may be date-codes on the can-caps.
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I really looked for date codes, one pot was all I could see without loosening them, was 1156. That seems about right. Seems just a skosk late for those escutcheon plates...but these things moved rather slowly back then.
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When you're hot, you are HOT! :worthy1:
You absolutely cannot beat free stuff. :icon_biggrin:
And that Lowery is a Beast of an amp. :laugh:
Big time score there.
Talk about heavy metal, the big iron on that thing has to weigh a ton.
No really, it looks like that thing weighs 40+ lbs.
I'm guessing it puts out around 50 Watts each on 2 channels? :dontknow:
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Well, I got the Voycall gradually fired up to full (345 B+) blast. It's certainly able to swing a big signal at highish volume, but's getting a massive bass feedback oscillation if the gain is turned too far up. As an amplifier, it largely works, certainly doesn't smoke.
The organ has 4 7591 Westinghouse, the coveted ones. Plus 20 or so RCA 12AX7A *and* a 12AZ7 for a new toob to play with.
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it sure doesn't right now, LOL. Note that the smaller transformer is a honkin filament tranny, to run all the oscillator tubes. The lower amp is pretty much a stereo amp all set to go with 12AX7 driving 7591 & dual OTs about the size of a 5E3 Deluxe. I've done lots worse.
I am almost thinking to sell the tubes (they go for 70+ a pair) and downconvert the amp to 6V6's which would luxuriate in those OTs. Make a nice creamy little home stereo. Or leave the fil tranny and use 12V6 which can be bought cheaply.
Here is a gut shot, by the way, not of mine, but a super clean identical. See how the tranny on the lower left only has black & green wires and feeds (only) the big interchassis plug? Filament tranny for the upper deck. Not unuseful. Not part of the amp.
(http://i172.photobucket.com/albums/w32/ttm4/lowrey_gut_shot_zps1780nn5p.png) (http://s172.photobucket.com/user/ttm4/media/lowrey_gut_shot_zps1780nn5p.png.html)
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And those 2 PP OTs on top look rather substantial.
If you can sell off some parts to fund the creation of 2 complete amps,
that would be the direction I would be heading in.
Otherwise, just converting what is there would lead to an awfully heavy head I fear.
Maybe if you built it into a big cab with coasters on it, that might be OK. :l2:
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It appears your Voycall amp was a good deal. :icon_biggrin:
I would have said that even without this confirmation. :l2:
http://www.ebay.com/itm/Vintage-Voycall-Sargent-Rayment-Mono-6L6-Tube-Amp-Amplifier-Rack-Mount-Guitar/151986175646 (http://www.ebay.com/itm/Vintage-Voycall-Sargent-Rayment-Mono-6L6-Tube-Amp-Amplifier-Rack-Mount-Guitar/151986175646)
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My Quad 6V6GT amp was delivered today. :happy1:
Unpacking it and a quick inspection using my Army inspired sniff test,
has me noting that all to familiar smell of burnt component.
I didn't see any obviously charred items, but will need to thoroughly inspect it tonight after work.
At least it didn't smell like burnt transformer, which I'm also getting to know all too well. :laugh:
It has 2 5Y3 tube rectifiers, the PT, and it appears to have two vastly different OTs.
A thorough cleaning and inspection should reveal more about what I bought. :l2:
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After a thorough cleaning and DeoxIt application, I tested the 6 tubes.
All the GE 1956 Black plate 6V6GT tubes test strong, as well as the 2 5Y3 rectifiers.
No schematic requires much wire tracing.
So after figuring out that one pin on a jack on one side of the amp,
needs to connect through a power switch to Pin 6 on a cable exiting the other side of the amp.
I put the good tubes back in and power her up, because I didn't find any burnt components and can't isolate that burnt smell.
I get her to power up and light the tubes.
I start checking voltages, and since the amp is upside down now I notice some of the DeoxIt residue bubbling in the bottom of a cap can.
Uh Oh, flip the switch, unplug the cord, and carefully touch that metal cap can.
Sure enough, she's hot as a pistol. I think I found my burnt smelling component. :icon_biggrin:
So I yank her out, and try the only other 30-10uf 475V cap can I have in my junk pile.
The replacement looks rough and very questionable too, but I don't have any other 475V E-caps, so I give it a try.
Same deal now, tubes light, I got +500V out of my rectifiers, this cap doesn't bubble (no DeoxIt residue) but it also gets very hot in short order.
Question on E-caps now.
Can I run say a couple of 20 and a 10 uF 350V E-caps in series to get a 30uF 700V E-cap equivalent? :dontknow:
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So the reverb amp came in today. :icon_biggrin:
Mailman comes late, so not much time before work.
Open her up and do the quick inspection.
No burnt component smell in this one.
Wipe off the tubes, 1 Bugleboy EZ81 rectifier and Bugleboy 6BM8, look good. :icon_biggrin:
No name USA made 12AX7 looks good, and 1 6BM8 non-Bugleboy is white on inside top and obviously bad.
Luckily I found 1 Philips Miniwatt 6BM8 in my tube collection, yeah 2 premium 6BM8s hopefully.
Will test all tubes prior to start-up.
A quick inspection of the reverb tank notes a wire on the input plug connection broken off.
Complete cleaning and inspection to occur after work.
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"Can I run say a couple of 20 and a 10 uF 350V E-caps in series to get a 30uF 700V E-cap equivalent?"
Yes, that's how it's done, though your calc is incorrect. It is important and necessary to place an "equalizing" resistor across both caps, one across each of them, just like on a Twin Reverb or Super Reverb. 220K seems to be the generally accepted value, and they act to produce a roughly equal split of total B+ volts across each cap, while acting as slowish bleeder resistors. Figure a Twin makes 450 volts DC. You run in effect, 440K to ground in the form of the two 220K resistors. So 1 mil flows through the stacked resistors. Don't go higher value resistor. I just put together an amp using stacked caps and the junk R's I had were 470K. Everything worked fine but for grins, I measured volts across each of the stacked caps. I was surprised to find (on a 400 volt right-out-of-the-rectifier supply that 375 volts appeared across 1 of the caps and a mere 25 or so volts appeared across the other. Rather surprising.
Guess what happened next? The cap with 375 volts across it blew. Fortunately, not violently, just oozing and sputtering black goo coming out of it. All components were salvaged, but I DO reform used e-caps with a doohickey I built that lets me put 75, then 150, then 225, then 330, then 425 volts across a "cap under test". It's just a power supply with a stack of gas regulator tubes on the output and some bleeder resistors and some current limiting resistors. It has a meter so I can read current into the cap. That ramps big on turn on but (should) go to near zero after several seconds.
As to your math, series caps do not add ufds. They act just as do parallel resistors. a 30 uf in series with another 30 would result in a net capacitance of 15 ufd. In a Twin Reverb power supply, you will see 2 qty 70 ufds stacked up in series. Those result in 35 ufd net. With (as per your example) a 30 uf in series with a 10 uf, the math is product/sum = net ufds. So: 30 * 10 / 40 = 300/40 or 7.5 ufd. You kind of do not want to use 10 ufds for this, since the net ufds will ALWAYS be less than the lower value cap.
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I really cleaned up the reverb amp pretty well.
Fixed the reverb, added 3 prong cord, and filled her up with premium Bugleboys/MiniWatts tubes.
Put an 8 ohm speaker on and gave her an input from my other amp. She is working!
It's not much of a guitar amp the way it is, sooo.
I decided to try to flip her quick on Ebay. Getting good pics, and working on the write up.
I'm going to try an Auction starting at $150 & shipping. Hell the Bugleboys it has are worth nearly that at tube fetish retail prices. :l2:
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Wurlitzer and Belvedere schematics?
Anyone know where I can purchase them?
I contacted a guy on Ebay that has tons of schematics scanned to DVD for sale.
I am hoping he will have what I need and respond soon.
The Wurlitzer has it's full circuit on it's chassis, except maybe vibrato and swell?
The controls are off chassis and need to be identified and installed.
The Belvedere is another enigma without a schematic.
It clearly does not have everything on it's chassis.
But that may be a good thing. :dontknow:
It has a rather large input transformer feeding the quad 6V6's.
It has a wiring harness and a couple of ports to deal with.
It looks like the wiring harness supplies voltage to the separate pre-amp.
This might be OK to mount controls and pre-amp tubes up at the top of a housing,
and then have the main amp mounted on the bottom of the housing.
I'd just need to develop a guitar friendly pre-amp that interfaces properly with the input transformer.
Without schematics though, I'm at a roadblock on both of these. :BangHead:
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If you are now going to destroy fine musical instruments, you owe it to yourself to visit http://www.organforum.com/forums/ (http://www.organforum.com/forums/)
Excellent resource for finding out FOR SURE if an organ is tube or silicon. usually you can tell from the non-garish flipper switches, but not always. On that forum, one typically finds "Hey I was given this Baldwin ____; does it have any value and/or is it worth fixing?"
Then someone chimes in with "I had one of those, it sounded like early transistor xxxxxxx and I gave it away" or, "those have a ton of tubes in them...."
I am taking apart this old Lowrey. It has about a zillion neon lamps and lots of seemingly useful parts. It's a ton of work to take apart, though.
I really don't want to take apart tonewheel Hammonds, just don't want to.
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I already registered on that organ site.
Unfortunately, it doesn't seem to have the info I'm looking for.
No plans to destroy any fine musical instruments, here. :laugh:
On the contrary, the plan is to use as much of these fine musical instruments, as designed, as possible.
That is why I am seeking to purchase schematics for them.
The goal is more to give them a contemporary make-over.
Utilizing the fine design/layout and adding the necessary components to give them new life.
The Wurlitzer appears to just need it's controls reattached.
The Belvedere was the entertainment console of it's day, not an organ.
The only organ I gutted was the Hammond H-100 with 3 amp circuits on it's chassis.
There didn't seem to be any point in trying to make that one, as it was designed, into a guitar amp.
The 3 OT's it had will be made into 3 complete separate amps. Seems the best option, to me.
My other boat anchor test gear purchases were always planned to be gutted for parts.
If I can develop a good guitar pre-amp for the Belvedere, there are a couple more of them on Ebay now.
I will try to reuse the plan to resurrect as many of them as people will buy. :icon_biggrin:
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I scrounged up some info on the Quad 6V6 Belvedere.
The main amp part I have appears to also be known as a Magnavox 101A amp.
This helps some, but I was hoping to find out what kind of pre-amp is feeding this input transformer. :BangHead:
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My reverb amp didn't sell. Oh well.
I've also learned a thing or two about selling items on Ebay with their return policies.
It's all good, until you run across an unscrupulous buyer. :sad2:
Then you are pretty much at their mercy.
And you will likely lose money and get a ding on your Seller rating.
So I don't think I will attempt to sell this amp on Ebay again.
I didn't have a schematic for it, but it was fully functional.
The issue is the 6BM8 output tubes it uses. A triode and Pentode in one bottle.
So to modify this amp to say EL84s, it no longer would have what it needs to drive the reverb tank.
It has the tube rectifier, a 12AX7, and the two 9 pin output tube sockets.
Any ideas for a PP EL84 circuit with reverb that I could convert this amp to?
I know I would likely need to add at least one maybe two sockets to drive the reverb tank and complete a preamp circuit.
I will also probably need to change the OT, but I've got one of those for the EL84s.
Maybe it's easier to just convert this to a PP EL84 amp without reverb? :think1:
I could use info on how I could possibly use this reverb tank with my 6L6 components.
How do I test the tank to verify it will work in a different circuit design? :dontknow:
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Old electronic instruments, especially signal generators. The cases/chassis make great 'lunchbox' amps, they can be found cheap, and as a bonus, one almost always finds other useful stuff inside.
What are your favorite old pieces of gear to buy for parts cheap?
I have gotten some from old movie projectors, record players, stereos, and radios. I'm looking to get some more power transformers, output transformers, pots, vintage tubes etc. from old gear for cheap. What do you guys like salvaging parts from? I haven't tried any old real to real recorders yet. Like I said if I can get gear that has a usable power and output transformer in them for cheap any tubes etc are just a bonus. What do you guys look for?
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Sometimes. The chassis and box are often the most usable items. I'm not saying it's impossible, but you're not gonna make much of an audio amp from a transformer rated to deliver 250 volts B+ @ 45 ma because it was spec'ed to run a 4-tube generator with a 1-volt output swing. I've taken apart my share of test gear and there are always exceptions. If you get it cheap enough, fine.
That said, many people look for old gear to salvage on the basis of parts inside. Don't overlook the box. It can be more useful than the parts inside.
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I agree that the housing is another valuable part to be considered.
I have a number of very nice rack mounting cases, that I would consider being free.
I mean the other parts I harvested from these buys have more than covered my costs.
Some of the boat anchor housings are difficult or impossible to use.
But even then the brackets and heavy duty metal could be cut and bent to meet a specific application.
Housings are a huge consideration for people like me without woodworking tools,
and considerable experience in making quality wood products.
I have a number of functional amps with no house to live in. :sad2:
I'm considering converting the reverb amp that didn't sell, into a Hoffman Stout.
I already have a component board made that worked on my breadboard.
I just need to verify the PT will supply the voltages needed, I've got an OT.
It would still need an additional 9 pin socket added.
But this chassis doesn't appear to be large enough to add another reverb driver tube and transformer.
I also was recommended to have reverb on any PP 6L6 amp I am considering building.
How can I determine if the reverb tank from this will work with a 6L6 design?
Will input/output resistance measurements get me the info I need?
Or are there other factors like impedance that are more important?
How do you find the impedance of an unknown value reverb tank?
I have learned how to figure the impedance of an unknown OT,
Thanks to the help I've received here. :worthy1:
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OK, with some searching of this forum, which I should have done in the 1st place, :BangHead:
I found Tubenit's thread on 1 tube reverb, which contained an excellent .pdf from Sluckey explaining reverb tanks in detail. :worthy1:
http://el34world.com/Forum/index.php?topic=7957.50 (http://el34world.com/Forum/index.php?topic=7957.50)
Once I can wrap my brain around this information, I should be well on my way to utilizing this tank. :icon_biggrin:
It appears that the little amp I have uses the transformerless 6BM8 circuit to operate this tank.
I think I will need to attempt to draw out the full circuitry of this amp this weekend.
I think I can manage that as there really aren't that many components.
If this indeed uses a transformerless 6BM8 circuit for the reverb,
would it be reasonable to conclude I could just add that circuit portion in front of the last gain stage of any amp?
There is a simple Champ circuit with the verb circuit on the grid of V1b.
If I wanted to try to add reverb to a PP 6L6 circuit,
would it work well on the grid of the last 12AX7 before the PI? :dontknow:
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Thanks to DummyLoad I have something to try to edit. :worthy1:
I am trying to document the 6BM8 amp starting from his K10.sch
I've only got the PS and output section documented so far.
Does that part look alright?
I've managed to input some new component values and voltage readings.
I wasn't able to change the pin #s on my edited 6BM8p symbol.
Is there a tube component library I can import somewhere?
Any other tips for using this software more effectively?
It's a work in progress.
Hopefully, I will be able to figure out how to use this well enough to completely document this amp. :BangHead:
No reverb transformer, but it doesn't appear to be 6BM8 driven. :w2:
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Yup, mainly grab them for the box and the chassis, but find lots of other cool stuff == those ceramic screw-in turrets are really handy. Some 12AT7s. Mostly obsolete tubes, but found one 6BM8 that I discovered was available again (still?), and that's become a focus of interest.
Sometimes. The chassis and box are often the most usable items. I'm not saying it's impossible, but you're not gonna make much of an audio amp from a transformer rated to deliver 250 volts B+ @ 45 ma because it was spec'ed to run a 4-tube generator with a 1-volt output swing. I've taken apart my share of test gear and there are always exceptions. If you get it cheap enough, fine.
That said, many people look for old gear to salvage on the basis of parts inside. Don't overlook the box. It can be more useful than the parts inside.
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Well I came upon the mother of all tube junkpiles. Probably 35-40 Fisher, Pilot, Bogen, and Radio Craftsmen tuners and amplifiers for $125. And about 2 dozen Nixie tubes (in their sockets!!!!) which fetch ebay money. People make clocks out of them. I have to say, the project value is kind of appealing but when you can buy a used LED alarm clock for $1 at a thrift store, I can't justify the effort.
I figure I will throw out 90% of it, but parts, parts, parts, and there are a ton of transformers. Not many tubes, most gone. Oh yeah, and a perfectly functional DVM (noname but appears to work fine) and lots of screwdrivers and allen wrenches and little tools.
(http://i172.photobucket.com/albums/w32/ttm4/cl_zpszdvppahe.png) (http://s172.photobucket.com/user/ttm4/media/cl_zpszdvppahe.png.html)
(http://i172.photobucket.com/albums/w32/ttm4/cl_002_zpsqzx0jtmc.png) (http://s172.photobucket.com/user/ttm4/media/cl_002_zpsqzx0jtmc.png.html)
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Very nice score! :icon_biggrin:
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Certainly a pile for the ages. I carefully waited until a rare CA day when it was pouring down rain to grab it, LOL.
One thing about this pile, there are pieces here that are worth zero and I mean zero. And those items, you find your ruthless mojo. Though again, lots of times the chassis is the most useful part. There are also fair numbers of tuners (no power amp) and those might appear to have a juicy power transformer but in general they do not go high like we want for a power amp. Sometimes < 300 VDC, maybe a SS rectifier will help. So they are impressive looking trannies that do little good. I *did* get some NOS 6.3 filament transformers, always useful, and some of a particular type of tranny I have been looking for, which are 125 volts + 6.3 say 2 amps, for small projects.
I was a bit disappointed in the seeming lack of output trannies. I would have loved to get 3-4 pairs of 7591/7868 Fisher output trannies. I would have been ecstatic had I gotten something like that. They *could* be in there among the boxes of pulled-out trannies but I will have to look closer.
I am going to try to whittle this pile down and sell some Fisher glass and nameplates and misc on ebay. There are 4 Fisher 800's in this pile, but no way am I going to try to rehab them, they are really gone.
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Prolly got well over a dozen of these switches. Tell me $18 for a switch isn't stupid?
(http://i172.photobucket.com/albums/w32/ttm4/fisher_switch_zpswp7blbqj.png) (http://s172.photobucket.com/user/ttm4/media/fisher_switch_zpswp7blbqj.png.html)
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Morelock's Organ responded to my inquiry to purchase the Wurlitzer 7011 schematic.
They sent me these scans and didn't even ask for any money.
I offered to send them a couple bucks through Paypal.
These seem to give me almost everything I need to convert this to a guitar amp.
The only part that seems to be missing is the connections to the 6 pin control jack.
Vibrato, Swell, and Speaker Jacks are documented.
Control jack seems to be a power and ground distribution port.
There are only 6 pins and pins 1&3 are tied to Ground.
Can any of you suggest ideas about how this last jack needs to be configured?
I appreciate any and all ideas, even if they are wrong.
They might help me figure it out.
It is interesting to have an amp with Vibrato and Swell circuits.
Just jumpering speaker jack pin 2 to 5 proved the amp is functional as it is. :icon_biggrin:
I'll be very happy to get this thing converted into a Rockin guitar amp.
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Here's a little 2XEL84 I built in an old signal generator cab -- also used the power transformer and other assorted parts...
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I like it jbefumo!
If you get a good price on a dead signal generator an amp like this can easily be made for under $100.
That doesn't count anything for labor, but it's hard to beat that price on an amp like this.
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Thanks, and yeah, it worked out well -- PT didn't quite have the current to drive the EL84s to full power, but still pretty loud. If I'd known about 6BM8s then I might have used a pair. (Come to think of it, I think I found my first example in there, but didn't identify it until later.)
I like it jbefumo!
If you get a good price on a dead signal generator an amp like this can easily be made for under $100.
That doesn't count anything for labor, but it's hard to beat that price on an amp like this.
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I've really slowed down on my junk tube gear purchases lately.
For two major reasons:
1. I am getting the assistance I need here,
to convert my pile of junk parts into rocking guitar amps that actually look like a guitar amp now.
This is a slow time consuming process, but I'm enjoying every minute of it.
2. The Ebay market has gone into the unreasonable price region again.
Items in not working/unknown condition with no returns accepted are being bid to prices
that could only be justified if the identifiable components were known to be good.
And then the prices don't meet my 2X value as compared to new prices criteria.
There was a time, not too long ago, I had a Watch list full of items that met my buying criteria,
but I didn't have the funds to take all the shots.
Now I seem to search long hours in vain for items worth buying.
Maybe this is the time I should be a seller instead. :l2:
I am having to revert to searching the fringe markets for anything potentially worthwhile.
I hope you are all still doing well with your junk tube gear purchases! :icon_biggrin:
Best regards,
Paul
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So I start complaining about not being able to find the deals :sad2:
And then it's like Manna falling from Heaven. :w2:
I had to grab all three of these items.
I even paid the BIN price on the HP and Cordova amp. :l2:
And now that I've already broken my budget,
the deals are popping up again. :dontknow:
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Some might wonder about the Recordio R-R. :w2:
It came in today, and I went right to tearing it apart. :l2:
It has a PT, SE OT, 6AQ5, black plate RCA 12AX7, Sylvania 5879, and a 6X4 rectifier.
The case is in good condition, with 2 small speakers that are probably not great for a guitar amp but we'll see.
So just these parts for < $28 delivered seems to meet my 2x new parts value buying criteria. :icon_biggrin:
I definitely did not buy it to have a tape recorder.
The case seems large enough to put a bigger speaker and maybe a 18W Stout inside. :think1:
The Cordova amp is listed as out for delivery now.
I hope I did as well on that one too. :w2:
As for the HP 214A's, I can't resist all the quality parts in these for < $70 delivered. :dontknow:
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You could corner the market on those HP 214s. Seriously, those are pretty interesting pieces of gear. Useful? Well....imagine one day you are retired, have a bunch of horses or cows on your farm, they are enclosed by an electric fence, and you wish to deliver a precision pulse to their hind quarters to prevent them from ramming the fence. Not too harsh, not too gentle. You're in business!
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I am the buyer of HP 214A's for sellers who just want to move their item. :l2:
I tore the 3 I had down to just parts last weekend. I'm getting pretty good at that.
They take up less space like that, and the parts are ready to reuse now.
29 tubes in there, usually Amperex made in Gt Brittan/Holland vintage.
3 12AX7s and 9 6DJ8s ensure a good value at my price. :icon_biggrin:
The PT has proven to be useable (maybe not ideal) for a number of amps.
It has way more capacity than necessary and runs extremely cool.
Top quality pots/knobs/wire/caps round out the valuable parts.
2 more PQ Premium Quality E130Ls bring my stock of those to 8. :icon_biggrin:
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The Cordova amp arrived.
I bought this mainly for the 2 12" Jensen speakers and the cabinet.
Hoping I can mount one of my amps in this cab.
Speakers look good so far, the cab appears to have water damage on the bottom.
I'll have to see what some Gorilla glue and clamps can do for that.
The amp that was on the bottom is still a mystery to me.
It appeared to have 4 octal sockets.
Two are octal, but one is 9 pin and the other 7 pin in the normal octal socket base.
The 7 pin has the AC in going directly to one of its pins?
Then it appears to use a SS rectifier and a fixed bias circuit. :dontknow:
Time for some internet research.
It is going to need to be torn apart anyway.
You know how the wires get that white mold type coating on them?
That needs to be torn apart to be properly cleaned at least. :icon_biggrin:
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OK, it's a Cordovox accordion tube amp.
The other two sockets are for plugs to it's tone generator.
Otherwise it uses 2 7591s and a 12AX7.
Stripped down it seems the PT/OT/chassis may be usable. :dontknow:
The 7591 data sheet shows fixed bias values from 350-450VDC.
I saw at least 1 450V cap can. A 400V B+ is a usable voltage.
The PT might have a monster 6.3VAC winding.
The tone generator had like 60 tubes in it.
Not sure if it had it's own heater supply or not.
Time will tell. Seems the Jensen speakers were well regarded. :icon_biggrin:
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The Jensen speakers sound good so far. :icon_biggrin:
I've got them connected to my Airline tube amp that I use on my computer now.
They do sound quite a bit different than the Peavey Mace speakers I have been using as my test speakers.
They seem to have less bass response, is what I have noticed so far.
It's too late for me to crank up the guitar amps with these new speakers tonight.
I expect they will sound really good when I hook them up to the Plexi tomorrow. :icon_biggrin:
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Actually it is easy to convert. Just cut out the tone generator. There are 2 raised preamp tubes which are used a Microphone inputs. Convert this to guitar inputs and cut away everything south of this.
The amp was made to have 6 chord tubes for Accordion and to work the tone wheel. You can forget finding a schematic. If you insert a signal you can pull tubes and only keep the ones providing the signal and the power section of course. Then you can simply remove all the other things. The tone wheel and driver tubes are not good for anything.
The Jensens are C12r. The amp was introduced at a time when companies were making instruments for Rock and Roll and the amp was cumbersome for a accordion player. Needless to say, not many were sold.
I did a low power tweed twin circuit in one that was given to me. I have since sold the amp to a guy who plays a lot of stones music and it really sounds good.
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I didn't get the tone generator, only the main speakers/amp cabinet.
The amp is in pretty rough shape right now, with the white mold and rusting on the transformers.
I'm thinking about mounting a HoSo56 (my next build hopefully) on top of this cab.
The moldy/rusty amp can wait until I'm ready to deal with it. :icon_biggrin:
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The Plexi seems quite a bit louder with these Jensen speakers. :dontknow:
They sound really good with it. :icon_biggrin:
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These little items are purchased for vintage parts, not repair/conversion.
So this one had 3 Webcor Made in Gt Brittan (can you say Mullard?) tubes.
1 12AX7, 1 7025, 1 12AU7.
All with the Mullard/Amperex X marks the spot tops from their manufacturing process.
Just one of these tubes could cost you what I paid for this item. :icon_biggrin:
There are 2 other USA made 12AT7s, and then the rest of the parts are just gravy.
This is where I get the majority of my tubes from,
and my stock consists of mainly these type of premium vintage tubes. :icon_biggrin:
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Latest score, not the worst ever for $125. Decent tube haul if they are OK.
(http://i172.photobucket.com/albums/w32/ttm4/livermore_score_zps0w6xtrad.png) (http://s172.photobucket.com/user/ttm4/media/livermore_score_zps0w6xtrad.png.html)
>>2<< qty Knight KM15 mono amps with cages *almost* in this good shape. 4x Mullard 12AX7 3x Mullard 6BQ5, RCA 6BQ5 Having two identical mono amps is worth more than 2x a single amp.
1 qty Bogen CHB 50, Mullard & RCA 12AX7, GE & Sylvania 6L6. Slightly futzed with but all there.
Goofy "don't plug this in" Admiral amp from console, EXCellent chassis metal to adapt for 5E3, P-P 50L6. Value = 0.
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I really like the sound of the Mullard 12AX7s! :icon_biggrin:
I just scavenged a few more of them myself.
Took a very long Sunday drive to Akron OH today.
Picked up another Cordovox just for the Jensen speakers.
This had the tone cab, but no main amp in the speaker cab.
Tone cab yielded 1 Mullard 12AX7, 4 USA 7025s, and 3 12AU7s.
And a ton of 6X8s, and 6FH8s, doubt I'll use these.
All for $40 and a 750 mile drive. :l2:
Listening to the speakers now. They sound very good. :icon_biggrin:
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With the Bogen, looks like the goofy (but nice) guy I bought it from just blindly put a 12AX7 in the socket that wants a 6EU7 and thought it didn't work. Well, with that tube in that socket, it sure won't. I don't have any 6EU7s so for now it goes on the PILE.
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6EU7s are hard to come by in junk gear.
I know I have 1 or maybe 2 in my stock now.
They are also rather pricey on Ebay. :sad2:
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Hey guys I got a nice deal on OLX site like Ebay down here, this weird amp for 80 bucks(about 20 US dollars), check it out!
Came with 4 tubes, 3 nice transformers all in good shape. Missing power tubes and rectifier.
Tubes are:
1 Telefunken ecc83 made in germany
1 unknown tube to me but it is a 9 pin tube with the looks of a 12a_7 type, it does have a fence like around the plates.
1 Sylvania 6SL7 made in USA
1 RCA that looks to be also a 6SL7 made in USA, inside looks exactly the same as the other one.
Lots of nice resistors, pots, switches, caps, capcans, etc.
I got the feeling that is going to be hard to find the schematic.
http://sp.olx.com.br/sao-paulo-e-regiao/arte-e-decoracao/amplificador-fidelius-179315524?xtmc=amplificador&xtnp=10&xtcr=7 (http://sp.olx.com.br/sao-paulo-e-regiao/arte-e-decoracao/amplificador-fidelius-179315524?xtmc=amplificador&xtnp=10&xtcr=7) pics no longer available at the link.
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Valvo EF86 I'd say.
You did very well on this, Score! :l2:
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I have bought a number of junk R2R recorders.
Most are SE 6V6 or 6AQ5 output circuits.
The OTs are usually 2.7K load at 8 ohms.
Obviously, I could make Fender Champ clones from these.
I wasn't quite satisfied with a 6V6 or 6AQ5s output.
I found another circuit that I like much better now.
An EF86 driving a metal 6L6 with a B+ of 250 VDC.
The 6L6 data sheet shows numbers for +250 V.
6.5 Watts output power seems to be fine with these little SE OTs.
At 250 V on my BB, I have no oscillation issues.
This sounds much better than a basic Champ to me.
I haven't tried any modifications yet.
Maybe the EF86 could be run a little hotter???
Or the 6L6 bias resistor could be reduced from the 265 ohms I used???
My bench supply says I'm pulling 55 mA of current for the whole circuit.
Data Sheet says 170 ohms self bias with about 85 mA maximum current used.
Any suggestions for improvement of this already well performing circuit?
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... junk R2R recorders. Most are SE 6V6 or 6AQ5 output circuits. The OTs are usually 2.7K load at 8 ohms.
I wasn't quite satisfied with a 6V6 or 6AQ5s output. I found another circuit that I like much better now.
An EF86 driving a metal 6L6 with a B+ of 250 VDC. The 6L6 data sheet shows numbers for +250 V.
... the 6L6 bias resistor could be reduced from the 265 ohms I used??? My bench supply says I'm pulling 55 mA of current for the whole circuit. Data Sheet says 170 ohms self bias with about 85 mA maximum current used. ...
Don't confuse "Zero Signal" with "Max Signal" numbers on the data sheet (http://www.mif.pg.gda.pl/homepages/frank/sheets/021/6/6L6.pdf) (unless you're measuring while playing full tilt). The old sheet shows 80.4mA total cathode current at idle. That's 170Ω * 0.0805A = ~13.7v bias at idle, shifting to/above ~14v at full tilt (due to distortion/rectification effect).
The real question is do you know what current your R-2-R power transformer can supply? You'd like to know if it can support the extra draw from the 6L6 (both on the B+ and the heater, which is doubled from 0.45A to 0.9A).
Even if it can't go all the way to the data sheet maximum condition for 6.5w output, the output of the present setup probably give you very similar sound-in-the-room.
If you could draw the extra idle current (by dropping the cathode resistor to ~170Ω), the 6L6 would be slightly easier to drive (~13.7v for 80.5mA through 170Ω vs. ~14.6v for 55mA through 265Ω).
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Changed bias resistor down to 172 ohms.
Now the PS is pulling around 70 mA.
It is a little louder, sounds a little better to me.
The difference to me is the clean volume.
The 6L6 stays cleaner longer and louder, but can still be overdriven.
The metal 6L6s get really hot though.
They need to have good ventilation in a small amp. :icon_biggrin:
I'm thinking most of the R2R PTs have should be able to power this 2 tube circuit.
Most of them had 4 or 5 tubes to power in their original design.
They were usually using a B+ near this +250.
I'm sure some of my PTs won't work for this.
But I think a number of them will. :icon_biggrin:
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For a SE output, I'm liking the sound of the 6L6 or bigger tubes better.
I like the 6V6/6AQ5/EL84 in PP configuration.
If I can get away with using most of my little SE OTs with a bigger tube I'll be happy.
I'll just have to pair up the little guys and get PP OTs for them. :icon_biggrin:
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Checked the Data Sheet for the EL34.
At 250V it has 11 Watts output at a 2K load.
Too much wattage for these little SE OTs, and not quite the right load.
Looks like a KT66 might work with 7 1/4 Watt output at 250V with 85 mA @ 2.2K load.
I don't have any of these anyway.
I put all my metal 6L6s and my 2 6L6Gs through this circuit.
1 6L6G and 1 metal 6L6 pulled 75 mA of current.
All the others pulled 70 mA.
Every single one of them sounded really good to me.
Much better than a basic 12AX7 6V6 Champ to my ears. :icon_biggrin:
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I checked my circuit voltages with my DMM, for more accuracy.
My bench PS showed 250V on its analog meter.
I got:
A = 258
B = 257
C = 255
What should I expect if I dropped the C node feeding the EF86 down some?
It is sounding really good to me at these values.
It is still on the BB so making little changes is quite easy.
Going just by ear, many small changes result in an imperceptible change in tone. :dontknow:
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Got some new toys to play with.
For $16.99 delivered, I decided to find out for myself about the little SS PA amps.
Now for the Bell PA.
Bell Sound Systems of OH, tube PA Model 5630.
I searched for the schematic online, Radiomuseum seems to have it but I'm not a member.
I couldn't locate it anywhere else for free online yet.
If one of you are a Radiomuseum member and wouldn't mind downloading this schematic for me.
I would greatly appreciate it.
Don't bother with this.
If I want to sell it to the Army I figure I'll need to include the manual.
Searched Ebay and got a good deal on one, $6.25 delivered. Done.
My plan for the Bell is to just restore and revitalize it with a new custom military paint job.
Then see if the Command here is interested in a cool USA made, restored and custom painted, PA tube amp.
My 2nd son just graduated from the on post HS.
The 500+ people in attendance at the Parade Field could not hear the speakers due to the crappy SS PA they used.
They might actually be interested in a better quality sounding tube PA with a custom Military paint job called the "Liberty Bell". :l2:
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Now you can download 3 schematics a day from Radiomuseum for free
Chose the apparatus you are interested on, click on the small image of the schematic that appears on the right, a bigger partial image of the schematic will appear, click on this image, insert your data and receive an e-mail with the requested schematic
Pay attention that if the schematic is splitted in more images you must repeat the procedure for each piece (remember 3 per day)
Ciao
Franco
p.s.: You have a Private Message
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Hey guys I got a nice one here. 1956 Tape recorder !
Model: 711 Tape-O-Matic - V-M VM Voice of Music
Valves / Tubes 6: 12AX7 12AX7 12AX7 6SN7GT 6V6GT 5Y3GT
One of the 12ax7 ,the print wore off, does anyone recognize the brand ?
Check it out :
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Looks like CBS (left) Tung-Sol (right) to me (lower pix) Upper pix looks like a Japanese tube.
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Sharp eye 11! :worthy1:
I missed figuring out the Tung-Sol, but now that you pointed it out.
I think that is what that has to be.
Most of my MiniWatt labeled tubes are from Holland,
but Philips could have made some in Japan.
I have some X marks the top 6DJ8s made in Japan. HP labeling I think.
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Looks like CBS (left) Tung-Sol (right) to me (lower pix) Upper pix looks like a Japanese tube.
Nice catch !! I still have to do the freezer trick , maybe the full print will show up.
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CA Historical Radio Society flea market tomorrow. I am really in de-accumulate mode and I dropped off a lot of stuff as a donation. But I saw two or three rooms of gear that was going to the flea market and there were some audio amps there with Fender Bassman trannies. The trick is to not buy back the same crap you just dropped off for donation! :icon_biggrin:
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What should I expect if I dropped the C node feeding the EF86 down some?
A bit late on this, it's a very long thread so I only check it out occasionally but...it's nice to see little treasures coming out of old gear. Also nice to see them not end up in the trash somewhere. But even with the best intentions I've managed to make a mess of things sometimes like having two superb ANOS black plate triple mica square getter 5751s. I got so excited, carefully cleaned them, and took them to my kitchen door to get a good view in the direct sunlight and I fumbled one right at the goal line. As it fell I tried to save it from hitting the hard unforgiving tile floor using my best hockey goalie and soccer style moves but it still hit hard enough in the right manner to break. :sad2: :BangHead: :cussing: a dumb $50 mistake give or take.
Lower voltages on a EF86 usually help cause it to break up earlier and lose headroom. Sometimes it can also help it to become or show more microphonic behavior as well by increasing it's gain. Since '86s have plenty of gain anyway I like running them at higher voltages and lower gain conditions and even running them clean in triode mode is like a really good 12AX7 stage. 5879s are also very nice which can be found in Bell & Howell equipment.
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Yeah, similar happened to me. I bought one of those early Tektronix 555 2-man scope power supplies at the last CHRS flea market for $5. One of these:
http://www.lemis.com/grog/Albums/Tektronix-555.php (http://www.lemis.com/grog/Albums/Tektronix-555.php) very bottom of page.
It looked like it was in decent shape. When I got it home, I could see some of the tubes were cracked. The 6080's? Nope. The 6AU6's? Nope. 3 out of 3 12AX7s were cracked and 2 were 5751! Argggggh.
Did decent at the flea market:
I *did* get the Fender-transformer thingy I saw, $35 for a 4-6L6 type amp with a HUGE Sunn (yes, branded "Sunn") power trans and a Fender Twin OT. Untested, build quality looks just a bit above average, who knows it might work.
$5 for a Heathkit IG-18 audio gen, untested but looks decent
$5 for a nice resistor decade box.
$5 for an unknown chassis with 2x RCA/GE 12AX7 and 4x RCA/GE 12AT7 and that number of Fender-type tube shields.
$$ damage not too bad.
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One of my best scores evah!! Fun.
hp 711A Power supply. I have wanted this particular model for a long time because it is small and will fit under the bridge on my bench. 500 v, 100 mils. Kewl. $5. Oh yeah, has 2 qty GE 6L6GC as pass elements. Very excited.
hp 521 counter. I know it may sound weird but I have wanted a counter like this (using the 4-12AU7 decade counters....either Beckman or Berkeley Scientific) ever since I used to wander onto Canal St in Lower Manhattan and find the internal decade boxes. That would be like almost 50 years. This was among the very first electronic counters that were available. With 7 extra decade boxes....and now....guess where all my Conn organ 12AU7s can go? Each decade uses 4 of them! $10.
Solavolt variac and constant voltage transformer. 50 lbs, in its own box. $15.
The other thing is A LASER!!! Free.
All this for $30. I am supposed to resist this incredible pile of crap??? No way.
(http://i172.photobucket.com/albums/w32/ttm4/2004-12-31%2023.00.00-5_zps8clketee.jpg) (http://s172.photobucket.com/user/ttm4/media/2004-12-31%2023.00.00-5_zps8clketee.jpg.html)
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You always seem to find the deals!
Now you just need a tank and shark to mount your laser on, Dr. Evil. LOL
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I'm always searching on CL for "oscilloscope" or "ham radio" or "vacuum tube" or "test equipment" or "organ" or "free organ" or "tube amp" and sometimes there's something there, often there is not. Had to drive 30 miles but the asking prices were silly cheap. There was no mention of the 521 counter nor laser in the ad, the counter was $10. Could not resist that (At least 20 12AU7s) I really only wanted the power supply as I had been looking for one for a while. The variac/CV transformer I really have no need for as I already have a variac, but $15 was just too cheap to pass up.
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eleventeen - I had two older hammonds I could have gotten for free in the last month. but I sold my 2x pickup and have no way to pick them up. So I had to pass. They were both tone wheel organs, although not B3s or the like. I think they were L series.
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I dunno, I kind of dislike the idea of taking apart old Hammonds, even if they are dirtballs like S-6 chord organs. I know they will require more effort and and time and $$ in service to make them work than they will ever be worth....and let there be no doubt, there is IMO no better source of (more, a greater quantity) used parts and stuff than old organs. I just don't like the idea of trashing the Hammonds and I'm not that happy about the amps you get of them, should you dismantle. I don't feel that way about CONNs or Lowreys, etc; I know the next guy will cheerfully take them apart and I don't criticize them....it's just that I myself kind of don't like to do so. Yes, it's weird. And surely, many are destined for the dump so what does it matter what I think? The other problem with organs is that they generate half a pickup truckload of crud you have to cart away.
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I thought would comment on the hp 711A and 521 pieces I bought for so cheap about 5 posts upthread.
Both items kinda sorta worked; After variac'ing them up, the power supply only went to 270 volts, the counter neon lights lit up but the counter would not self-test properly and was otherwise frozen. I opened them up and each one had 2-3 bumblebee caps. I lifted one end of all of them and half were sort of leaky. I shotgun-replaced 3 of those caps in one and 3 of those caps in the other and voila, both items work fine now.
Those caps are quite simply "always suspect".
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I thought would comment on the hp 711A and 521 pieces I bought for so cheap about 5 posts upthread.
Both items kinda sorta worked; After variac'ing them up, the power supply only went to 270 volts, the counter neon lights lit up but the counter would not self-test properly and was otherwise frozen. I opened them up and each one had 2-3 bumblebee caps. I lifted one end of all of them and half were sort of leaky. I shotgun-replaced 3 of those caps in one and 3 of those caps in the other and voila, both items work fine now.
Those caps are quite simply "always suspect".
I bought a "working" 1958 HP-400D AC VTVM about 5 or 6 years ago for $15. The electrolytics in the power supply were fine, but all the coupling caps (scarlet colored Chiefs, IIRC) were leaky. I shotgunned them all, and it worked fine. Darn, HP wrapped those leads around the terminal strip lugs very well.
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Who lives near Poughkeepsie, NY and likes to scrounge old tube stuff?
Good pile of crap: $59. The hp transfer oscillator has a lot of good parts.
http://www.ebay.com/itm/LARGE-VINTAGE-LOT-NAVY-Signal-Corps-HP-OSCILLATOR-Oscillograph-More/201657184860?_trksid=p2046732.c100040.m2060&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20140107095009%26meid%3D08bb69528ece42a7a0f6828332f48f7e%26pid%3D100040%26rk%3D2%26rkt%3D4%26sd%3D262587435023 (http://www.ebay.com/itm/LARGE-VINTAGE-LOT-NAVY-Signal-Corps-HP-OSCILLATOR-Oscillograph-More/201657184860?_trksid=p2046732.c100040.m2060&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20140107095009%26meid%3D08bb69528ece42a7a0f6828332f48f7e%26pid%3D100040%26rk%3D2%26rkt%3D4%26sd%3D262587435023)
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OH THIS IS PROBLEMATICAL!
(http://i172.photobucket.com/albums/w32/ttm4/lowrey_zpsryp6w1cv.png) (http://s172.photobucket.com/user/ttm4/media/lowrey_zpsryp6w1cv.png.html)
Here's an organ speaker cabinet with a dual 6550 tube amp in the bottom for $125. Check out the GZ34 with metal base. Yow!
Metal based GZ34 sell for over $200 on ebay. That tube would pay for the whole thing and 2-way gas.
It's only 185 miles away. Yeah, there's a funky looking 15" speaker and a horn and a HUGE crossover network too.
I just may have to go get this.
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The vintage GZ34s are insanely priced on Ebay.
What gives, is it some kind of tube fetish or what?
It is just a rectifier tube after all.
I just picked one up tonight, hidden in a larger lot of 65 tubes for a total price of $26 delivered. :icon_biggrin:
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Well, there's fetish and there's fetish. But you can find half a dozen examples of metal-based GZ34 not just selling for but which actually sold for upwards of $200 so I don't argue. I am frantically looking for other tubestuff located where this cabinet is to see if I can get more junk on the trip.
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... I couldn't let it slide by again.
... I call it the SwollenSack
... For less than $25 you can't go wrong!
It's taken almost a year and a bit over $27 but persistence pays off? We shall see? I haven't got it yet to see what it's all about but thanks for tip!? Do you do anything special with these or just scavenge out what you can use?
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JoJo,
There are a few different designs of these, some SE some PP, but all usually contain 3M labeled Mullard GB tubes.
I have just modded one of these, and have another still in my pile.
It's a heavy beast that doesn't look much like a guitar amp as it is.
I plan on stripping the parts to put in a more traditional design in the future.
Plenty of quality parts to justify your $27 delivered price.
I think you will be satisfied. :icon_biggrin:
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Knight pwr/pre, vol, treb bass, beautifull shape, cage-tube cover looks New w/quick coat of grey primer from can...110.00, w/2 Millard el84's, &2 bugle boy 12ax7's!!! All strong, no mention of them in ebay ad. Goodwill 25.00 R2Reel, Grundig/Concord, something like that...2 more bugle boys, 12ax's, 2 6ca7? ...the ones people make the headphone amps out of, and an intact 2 Speed Motor that looks just like the ones that come out of the vibratones, along with tons of heavy duty metal, angle , n high quality CC resistors and rotary switches like2 pole, 6,8,10 throw... heavy duty cast frame speakers, albeit small like 6 or 8 inches, and a large heavy duty cabinet suitable 4 a portable extension cabinet or with the metal mesh vents,a vibro type cab. The thing was silly heavy built like a tank. Also a couple of view meters.... the Knight sounds great...mono, love to get another one, run 1 on it's own speaker, dual mono block style. It only needed a cap can change. Actually only 1 of the smaller value ( something like 20uF @ 150) had gone bad. The higher voltage and microfarad Elektrolytics, and one smaller value in the can we're okay but I just changed them all. As far as the jrc4558 chips they are in all kinds of stuff cheap radios and the boss red power supply. Those rip offs of the scholz Rockman have a few MN 30007 and whatever variants... they are those red housing rip offs of the scholz Rockman, but if you're into that they actually sound pretty good. I love old broken computers for their power supplies ribbon cable push button switches that are like the same ones on DigiTech multi-effects, not to mention some have a great fans.. and those Square switching power supplies make great bench power there's a bunch of tutorials on YouTube you basically just run the little female connectors that Doug sales here, the kind that fit your probes and a way you go.
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Next victim:
(http://i172.photobucket.com/albums/w32/ttm4/tek_rm35_scope_zpsit7lcmix.png) (http://s172.photobucket.com/user/ttm4/media/tek_rm35_scope_zpsit7lcmix.png.html)
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I think you will be satisfied. :icon_biggrin:
Que the French horn...Waa waahh. I got hosed in that I was unaware these were actually made with transistors too. Who knew? My own fault for not asking questions I guess? But people selling these things don't know anything about them either. Buyer beware...
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As one who trades stocks for his living, all I can tell you is, make all the $27 mistakes you possibly can.
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Ha! Yeah not a big deal at all. I can either test it out and who knows maybe even have a 10w or so transistor amp? :huh: I could employ it for the rare occasions I need to signal trace something? Or need to record a super clear pristine jazz passage? :laugh: Or who knows maybe someone else will actually want it and buy after knowing it at least works or for parts? please see below:
Notice - For Sale: one fine *SS/SwollenSack tape recorder for cheap???
*(SS=solid state)
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I really try not to buy stuff on ebay unless I know for absolute sure its toob. I just hate paying shipping. Vastly prefer Craigslist. I am not saying I like driving 400 miles like I had to for that cabinet, above, but that worked out nicely. The metal GZ34 tests as if brand new and I mean brand new, and the 6550's test about 95%. As for the scope, I am working with the seller who lives about 150 miles away, he occasionally drives down to my area. That scope has 22-24 6DJ8 in it. And 4-5 12AX7s. The plug in has 3-5 12AT7.
Sometimes those old Tek scope plug-ins have some nice parts. But you have to get them cheap and if they are $25 to ship, it doesn't work.
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Check out this hit guys !! Traded for a old computer and printer !!
Looks like it does have a PP 6v6 power amp, a 6K6, the recto tube is a 5U4, looks good for a conversion !!
Geloso radio with pickup.
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Nice
Model of the radio ?
Franco
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Looking good Uki!
I haven't been posting much lately,
but here is my most recent Ebay buy.
Another great deal. ;^)
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Nice
Model of the radio ?
Franco
No Idea, I'm too wanting to know that, so to search for schematic would be easier, the only Obvious thing about it is the name Geloso, which is Italian manufaturer.
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K might be able to help you with that schemo.
But if your goal is not to have a radio that can also be used as a guitar amp, then it's likely unnecessary.
If your only looking to convert this to a guitar amp, then you will probably be taking out the radio tubes/circuit to make way for your pre-amp.
The full output section could likely be used as is, and is rather easy to trace and document that section.
With your output section documented, you could look for and likely find many guitar amps that use it or something very similar.
It does appear to be a PP 6V6 output section, so lots of guitar amp circuits will be similar. :icon_biggrin:
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Uki you say
2 x 6V6 - 1 x 6K6 - 1 x 5U4
but I count 7 sockets
Which are the other tubes ?
EDIT: Also a good photo of the dial plate may be of some help
Franco
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Uki you say
2 x 6V6 - 1 x 6K6 - 1 x 5U4
but I count 7 sockets
Which are the other tubes ?
EDIT: Also a good photo of the dial plate may be of some help
Franco
There are 9 total, 2x 6V6GT, 1x 6K6GT, 1x 5U4G, 1x ECH42(out of the socket), 1x 6SG7, 1x 6H6, 1x 6J7G, and another without a print. Look the picture.
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OK Uki
9 tubes
one, due to the position, seems a magic eye, do you confirm ?
you say 1x 6SG7 and later 1x 6SG7, how many 6SG7 tubes are there ?
the missing tube is a noval and all other are octal ?
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If you can a photo (a closeup) of the Dial Plate can help to identify the model
Franco
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@Franco
Ooops that was a misstype!! One of them is 1x 6J7G and 1x 6SG7. Post is fixed.
The missing tube is octal but small socket it is the ECH42 I removed the tube and left it out.
I found this link with many Geloso papers: http://www.arimi.it/storia/bollettini-geloso/ (http://www.arimi.it/storia/bollettini-geloso/)
Been looking one by one...
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OK, also I'll give a search
and I've ask also to some friends, I hope we can find it
Franco
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> looking one by one...
"Annuals". (Actually several per year.) Bo100 is a very modern tube and transistor model line. Up past B020 is pre-Octal tube types. First 6V6 seems to be Bo24, but I do not see a rig that fancy. Am looking at Bo26 but I should be outside.
EDIT- that cabinet is possibly post-War. B035 is Autumn 1940. Bo36 is April 1946, early post-War days. Bo36 page 7 shows push-pull 6V6, but not your full line-up (ah, this is a microphone amplifier).
ECH42 appears in Bo45, but in a 6V-12V radio (probably for car). Your ECH42 in an otherwise all-USA lineup is odd. I wonder if it was supposed to be a US type, but tube shortage at factory or in later years caused a change.
I would not have high hopes for "Short Wave", unless you have deep experience restoring old antique radios. The precision tuning needed for >1MHz does not hold up over the years, phenolic breaks, wax sags. Also 1938 SW was CW or AM; today it is largely SSB or code chirps. There must be a few long-range propaganda transmitters still on the air, but fewer every year. (And they probably have a clean reliable web-service.)
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> looking one by one...
"Annuals". Bo100 is a very modern tube and transistor model line. Up past B020 is pre-Octal tube types. First 6V6 seems to be Bo24, but I do not see a rig that fancy. Am looking at Bo26 but should be outside.
I would not have high hopes for "Short Wave", unless you have deep experience restoring old antique radios. The precision tuning needed for >1MHz does not hold up over the years, phenolic breaks, wax sags. Also 1938 SW was CW or AM; today it is largely SSB or code chirps. There must be a few long-range propaganda transmitters still on the air, but fewer every year. (And they probably have a clean reliable web-service.)
Thanks for the input PRR !!
I'm only interested in the amplifier section of it, I was trying the other day to catch some SW station in a modern radio... nothing.
Several caps about 8 are cracked and bleeding the insides, the schematic would help with the values, at least for the amp section, which looks to be a PP 6v6. No preamp tubes on it, curious, the audio signal goes directly to the power amp ?
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I have covered so far Bo1to Bo3-4; Bo50 to Bo75; Bo85
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AM radio, the detector outputs about 1V of audio. You need one voltage-amp stage to get up to 6V6 grid level.
In days of 78s, a phono pickup was a beast which chewed shellac to make about a 1V signal. You just switched the phono pickup in place of the AM detector.
For guitar you want one more stage. You can re-purpose an IF stage. Triode-strap the pentode and use Champ-like cathode and plate loads.
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Bo31, Super G.91, is push-pull 6V6, paraphase inverter, basic AM/Phono switching. 6Q7 diode runs through IF winding to 0.1Meg to 5-way switch. 4 ways are AM, one way connects the oval FONO input. This to volume control, then 6Q7 triode grid, and so on like any old amp. Another pot either shunts highs from triode plate, or doesn't-shunt highs from volume pot tap. OT is on speaker *and* that connector has *Wall Voltage* on it!! (so it can't be run with speaker disconnected.)
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A model that can be a bit similar is the G901
(http://i.imgur.com/cC47Lj8.jpg)
but only a bit
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A friend told me that may be it was a model build in Argentina and if so, it may not be on the Geloso Bulletins
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If despite all you don't find the schematic, you can use the PT, OT and power tubes to build an amp (a 5e3 ??)
Franco
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This one looks much like it and has 9 tubes. different cabinet without the turntable and all but it may be the same schematics. 1949.
http://www.radiomuseum.org/r/geloso_super_g901st_g901st_g901.html (http://www.radiomuseum.org/r/geloso_super_g901st_g901st_g901.html)
Did someone add the radio to the record player cabinet or was it al built by Geloso?
Guess its the same as kaliegsto posted. :icon_biggrin:
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I did build a modified Ampeg R-12 with the 6SL7 PI driving a PP 6V6 output section.
I really like the tone of that output section! :icon_biggrin:
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Thanks for the inputs guys !!
Yeah the plan is to use the power section and add a preamp to it, conversion like, the schematic would help but I still can draw it by looking at the circuit although some component values will be missing but that can be worked around, I'll make a thread soon for this specific topic, it is going to be an amp definitely !
@EKDENTON I did saw that one too before, been searching for about 3 days now.
Looks like the whole thing was mounted here, the pickup was a Garrard(England), the speaker is a Hamilton(US), and the machine is from Geloso but the dial plate is for the stations for the epoch back then and in portuguese.
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Whoa! Blast from the past!
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Score !!
Check out guys !! 1961-1962 Tape recorder Geloso G268 !
2x 12ax7 Phillips Miniwatt
1x 6AQ5
3x Iron and components !!
http://www.radiomuseum.org/r/geloso_registratore_per_alta_fe.html (http://www.radiomuseum.org/r/geloso_registratore_per_alta_fe.html)
http://www.arimi.it/wp-content/Geloso/Bo81.pdf (http://www.arimi.it/wp-content/Geloso/Bo81.pdf)
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Nice! :icon_biggrin:
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Nice Score Uki, I like it !
Give a look here
http://el34world.com/Forum/index.php?topic=17100.msg170616#msg170616 (http://el34world.com/Forum/index.php?topic=17100.msg170616#msg170616)
http://www.mediafire.com/file/2a6od9aevwco71m/Geloso_G258_Combo.rar (http://www.mediafire.com/file/2a6od9aevwco71m/Geloso_G258_Combo.rar)
Ciao
Franco
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Hey Franco !! Thanks for the links man !!
I'm very happy with it, now looks like I finally have all parts for a small amp project !!
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I'm not with the tape recorder preservation society. :icon_biggrin: Picked up a V-M 733AV R-R has a couple 6eu7's - 12au7 - 6bq5 - 6ca4 - Ray tube - 600v PT - lamp. All tubes are V-M except 12au7 all very clean. The people that built it must have needed sunglasses. I'm new at this so these parts will wait , till I'm done with a Kalamazoo Model 1 build. The scary part of buying these things , is people plug em in an say it works. My first donor was a Silvertone R-R I swear it was stored in a chicken barn. Got a 1958 Wollensak T1500 , really just an odd machine it's my least favorite. Not a good conversion amp the OT might be useful.
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As an FYI, I am likely to post this monster on eBay will go complete with outboard preamp section. Unless one of you guys wants it
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You will get better at this converting junk into a rocking guitar amp with more experience.
Voice of Music stuff usually has quality transformers at a minimum.
If you are picking these things up for $30-$40 delivered,
you can continue to build up an inventory of quality parts.
They will patiently wait on the shelf for you to gather the
knowledge, skills, and abilities necessary to convert them.
They also usually have quality vintage tubes that are worth much more than the new Chinese or Russian stuff.
The Swollensak, as I call them, is it a PP 12AB5 output circuit?
They are built like a tank, and the ones I got mostly had rebranded Mullard tubes in them. :icon_biggrin:
V-M tubes are rebranded, if made in Gt. Britain or Holland they are premium tubes.
If this is what you also got, then you have all the major components to make a nice guitar amp.
It is just not a very friendly housing for a guitar amp.
Putting those parts in a nice chassis and housing will create an amp you can be proud of.
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Top price I've paid delivered is about $32. I did just buy a PR-40 power supply for $45. on eBay.
The Wollensak is a push-pull amp , the PT is like half of a PT and half Widow maker? I recapped it before I looked at the schematic better I'll leave it intact until I learn how to build something with it's parts. There's a few jacks and a couple of caps that are probably usable.
The V-M has those two 6eu7's yep they're made in Great Britain (need to have em tested). Not much of a collector , my guitars are all pretty cheap , my favorite amp is my H&K Attax 80 lol I do love the sound of these tube amps.
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2 Mullard 6EU7s can sell for more than you paid on Ebay.
But if you're like me, you want just add them to your stock of premium tubes.
When you get ready to build your parts in a new chassis,
and use those tubes in your circuits you will be pleased with their sound. :icon_biggrin:
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2 Mullard 6EU7s can sell for more than you paid on Ebay.
But if you're like me, you want just add them to your stock of premium tubes.
When you get ready to build your parts in a new chassis,
and use those tubes in your circuits you will be pleased with their sound. :icon_biggrin:
They don't eat or drink my beer ;) The local shop here only has one kind to pick from and they're $34.95 each :)
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A couple of scores to :icon_biggrin: about. A Silvertone 7072 Reel-Reel $15 Habitat store 12AX7-12AU7-6V6GT-6X5GT all Silvertone tubes. Small Iron
Nice size , like new PT and OT from a Voice of Music VM714 Reel-Reel ran 3-12A_7's, 1-6v6 & 1-5y3gt ....... $27 eBay :icon_biggrin:
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Few days ago I got a Reel-Rell Grundig TK16 Recorder for 20€
I'm not so happy because I was hoping in a better OT, however this is what you can recover from one of this recorders (if you find one)
an EF86 (and this may be a good thing)
a pair of EL95 (6aq5) one was used as power tube
an ECC81 (12AT7) and an EM71 (loctal socket Magic Eye)
The PT is small but nice
1 x 6.3v winding with CT @ (at least) 1A (feeds EM71 - ECC81 - 2 x EL95)
1 x 6.3v winding with 100R Hummpot @ (at least) 200mA (feeds V1, the EF86)
I didn't measured the other two windings, but on the TK16 schematic the rectified voltage is
1 x 27v DC @ (at least) 85mA
1 x 270v DC @ (at least) 42mA
OT is small and the spec of the recorder say about around 2.5W output power
Oh, not for me, but if someone is interested on building a Record Turntable the motor is very nice and sturdy
(http://galerie.magnetofon.de/albums/userpics/10014/Grundig%20TK%2016%20Innen.jpg)
May be I'll be able to recover also the cabinet, but it has large rounded surfaces and I'm not sure it will be possible to cover it with tolex
(at the moment the coating isn't in good shape)
Franco
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Looking at the speakers these things are driving you can't expect much in the OT. I've run my little Silvertone tape recorder amp 12AX7-6V6GT-6X4 cranked into the little OT that was with it. 5k pri - 8ohm The spec'd replacement parts are Merit A2900 , Stancor A3856. both 4watt universal OT's. 2-4 watts is pretty loud thru the right speaker. :icon_biggrin:
Could of bought a big console stereo 4-6BQ5's -$75 but my son didn't seem to enthused about loading it up and lugging it home.
We brought home a big Hammond organ years .... ago it must have weighed 350lbs. My back was bad before that ... too dumb to realize what was in it. Now I'd have to hire someone to fetch one of these monsters home and pay em to haul off the carcass. The smell :l2: of these old tape recorders is like :lipsrsealed: I need an intervention.
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I was not expecting a big OT, only, some time ago, I got a Reel-Reel Philips EL3516/42 (that uses an ECL82 as power tube)
that is claimed to be 2.5W output power and the OT on this recorder is near dubled in dimensions (570gr = 1.25lb)
respect the Grundig TK16
So, if you score a Philips EL3516/42 is a good thing :wink:
Franco
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I was not expecting a big OT, only, some time ago, I got a Reel-Reel Philips EL3516/42 (that uses an ECL82 as power tube)
that is claimed to be 2.5W output power and the OT on this recorder is near dubled in dimensions (570gr = 1.25lb)
respect the Grundig TK16
So, if you score a Philips EL3516/42 is a good thing :wink:
Franco
Some of these things have an extension speaker jack and have a PA feature. Don't get much European stuff here , see stuff from Germany listed but , it's pretty expensive and shipping. The early 60's Japanese stuff is really , I don't want to use the word cheap. Haven't burned up my Japanese Kalamazoo yet .... knock on wood. :laugh:
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A couple of scores to :icon_biggrin: about. A Silvertone 7072 Reel-Reel $15 Habitat store 12AX7-12AU7-6V6GT-6X5GT all Silvertone tubes. Small Iron
Nice size , like new PT and OT from a Voice of Music VM714 Reel-Reel ran 3-12A_7's, 1-6v6 & 1-5y3gt ....... $27 eBay :icon_biggrin:
I ordered a Sams on eBid for the VM714 PT/OT 14 days ago nothing has arrived. Had to go to Paypal to file a case.
eBay usually takes care of this sort of thing for you. With eBid your on your own :cussing: Satisfied customers rarely talk about good service , dissatisfied customers , ... well ...... :cussing:
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Getting into the Silvertone model 7072 tape recorder it's an oddball no photofact I see one for a 7074 Didn't want to start a thread for this build until the OT is sorted out 2" x 1-5/8" winding is about 1-1/2" another sub 5watt OT :wink: 2.5watts maybe. The PT is pretty small
The schematic is better than usual lol. My dilemma is the OT I'm assuming yellow is positive , green is negative , and black is a ground ? ...... haven't seen this before. I'm guessing it's a preamp out? (TRS)
secondary:
yellow to green is 0.9ohms 0.04mH
yellow to black 9.65ohms resistor
green to black 1.1ohms 0.09mH
Primary
red to blue 432.5ohms 19.70H
Any help would be greatly appreciated
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Ciao Phil
Here a bit more readable image of the OT
(http://i.imgur.com/BtkFDbm.jpg)
Primary
B+ connected to Red
Plate connected to Blue
Secondary
Black connected to ground
Speaker (two speakers in parallel) connected to Yellow (so seems)
Speaker other pin connected to Green
I'm not able to read well the schematic, but seems that secondary has a very low impedance
are you able to measure the Turn Ratio of the OT and compute the impedance ?
With 205V on plates of the power tube I think we can espect around 5.5K of primary impedance
You have 1x 12aU7 +1 x 12AX7 + 1 x 6V6 + 1 x (what seems to be a) 6x4 (is it ?)
So PT has, at least, 1.65A of current for filaments and .... ??? may be 40mA B+
If you use all the tubes you can build .........
An AA764 ?
(http://www.thevintagesound.com/ffg/schem/champ_vibro_aa764_schem.gif)
(http://www.thevintagesound.com/ffg/schem/champ_vibro_aa764_layout.gif)
Franco
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... My dilemma is the OT I'm assuming yellow is positive , green is negative , and black is a ground ? ...... haven't seen this before. I'm guessing it's a preamp out? (TRS) ...
Green-to-Black is the full secondary winding (impedance unknown).
Green-to-Yellow is marked 1.6Ω; when nothing is plugged into the Output Jack, the pair of 3.2Ω internal speaker are in parallel from the Green-to-Yellow on the OT secondary (3.2Ω || 3.2Ω = 1.6Ω). The output jack has a switch to disconnect the internal speakers when something is plugged into the Output Jack.
The Output Jack provides output to (presumably) and external speaker with the OT secondary from Green-to-Black. There's also another output at that jack which is not entirely clear to me.
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The 7074, also if there is one more tube, is very similar
may be this schematic can help to understand better the 7072
(http://i.imgur.com/SyseM1F.jpg)
Franco
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I need to learn to read these things better (Green-to-Black is the full secondary winding) I don't have a Variac to check these things out :BangHead:
Wouldn't it be logical to use the whole winding? It is a TRS jack so maybe they have some weird combination of using internal and external at the same time. The measurement green to black , is the same on my Silvertone 2230 OT , which is 8ohm. I'm gonna go with the bigger measurement green to black 1.1ohms. These are resistance measurements. I was trying to find the link to a site where they discussed how to tell if a OT was good or not and they were trying to interpret what 8 ohms and 4 ohms showed for resistance on a VOM. 4 ohm being less than 1 ohm.
Well the PT is good :icon_biggrin: It's a 6X5GT rectifier.
By the way thank you :smiley:
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The 7074, also if there is one more tube, is very similar
may be this schematic can help to understand better the 7072
(http://i.imgur.com/SyseM1F.jpg)
Franco
Thanks for sharing that schematic :worthy1: as soon as I get the Photo fact on the Voice of Music VM-714 , you know where to find it. Left is VM-714 PT , middle is reverb OT , far right VM-733 OT , bottom right is VM-714 OT.
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Ciao Phil
Ah, OK, so it is a 6X5
here the spech
(http://www.mif.pg.gda.pl/homepages/frank/short/001/6/6X5.gif)
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.... I don't have a Variac to check these things out
You really don't need a Variac for that purpose, you can simply use a low voltage transformer (also a 6.3v will be fine)
Feed the secondaries of the testing OT with the 6.3v (measure exactly how many volts there are on the secondaries) and then measure the voltage at the primary
Divide the primary voltage for the secondary voltage and you obtain the turn ratio
Give alook here
http://www.radioremembered.org/outimp.htm
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Wouldn't it be logical to use the whole (secondary) winding?
Yes, it will be, but is better if you wait for some other opinion
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I didn't understand well ..... do you need the Voice of Music VM-714 schematic ?
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I was trying to find the link to a site where they discussed how to tell if a OT was good or not ......
is this of any help ?
(https://www.vintage-radio.net/forum/attachment.php?attachmentid=40460&d=1284535236)
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....... they were trying to interpret what 8 ohms and 4 ohms showed for resistance on a VOM
To use resistance to know which is the impedance value isn't a good idea, a transformer hasn't a fixed impedance, it has a turn ratio
reflected impedance to the primary depends on turns ratio and load impedance connected to secondary
so if a transformer reflects 4K to the primary with 4ohm load connected to secondary, the same transformer reflects 8K to the primary if you
connect an 8ohm load to the secondary (and so on)
Franco
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I'll need to make a rig with my spare 6.3 ....... these computers have great calculators. So doing the odd math would be easier than doing it with my Abie normal brain.
I've seen it done but , by placing the voltage on the primary. Then reading the secondary?
It's logical to apply the voltage to the secondary (AC) then read the Primary(DC)
I'm waiting on some clips , terminal blocks and a better meter so somebody stop me before .... :rolleyes:
I really love re purposing old tape recorders. It makes you feel nostalgic and evil all at the the same time. Gives you a little revenge , on the old crappy pulleys and belts that dashed my dreams of becoming a hair do sequined suit with a guitar. The Egg shaped sound wobbling ...... :cussing: ....... If I run across a really nice good one I'll save it. These things will have a second life beyond me ......
I'd really like to just get costs out of them here to some of the local musicians eventually. Tailor them to the sound they want. I don't have a wind tunnel but we're not going to fly these things .... they are tiny Maybe build one for my Granddaughter. Having ballpark idea's of what specs are on them is kinda important seeing what we go through to find them.
Yes I need a Photofact on the VM714 the colors are faded but it looks new. I've got 4 wires coming out the primary side of this thing and wondering what they are. 2 Black 2 yellow. I've got the other side sorted out. 5v, 6.3v, HT ,CT . Then there's always the OT. I ordered Photofact again on eBay and expect it soon. These are really nice transformers (pt 3" tall x 2-5/8" wide x 3-5/8 bell to bell 2" thick lamination 4lbs on the bathroom scale lol. Don't want to mess these up and was hoping to get a current rating on the HT and some idea of what the wattage is on the OT. Could be a nice SE or get a PP OT if the HT current is there. I got those loose , the seller said they came from a VM714 tape machine. 40-50mA is the norm for most everything I've got so far.
I haven't done the neon bulb test on these but I've done that on another set.
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The calculations are very simple
divide the Primary voltage for the Secondary voltage to have the turns ratio
multiply the turns ratio for the turns ratio
multiply the obtained number for your speaker impedance and you obtain the primary impedance (using that speaker)
200 : 6.3 = 31.746
31.746 x 31.746 = 1007.8
1007.8 x 4 = 4031.2
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It's logical to apply the voltage to the secondary (AC) then read the Primary(DC)
Errr.... no, my council is to connect the 6.3v to the secondary because this way the voltage you have on the primary is not very small
is a way to have a more readable voltage on the Tester and easier to be used for the calculations
So you are looking for the Voice of Music VM-714 schematic (if I've understand you correctly)
(http://i.imgur.com/7uVVxi6.jpg)
There are
1 x 330v - 0 - 330v AC and the schematic specify 60mA DC (I think about 100mA AC but we are interested in DC mA)
1 x 6.3v with (at least) 300mA
1 x 6.3v with (at least) 1650mA
1 x 5v with (at least) 2A
Franco
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:icon_biggrin: Thank you , I think I understand now , and thanks for the schematic.
I'm hoping the Photofact will be as good as the one I got for the Silvertone 2230.... with a parts list , replacement specs. Maybe that one is an exception , we'll see. I need to build a better prototyping rig lol instead of my 6AQ5 amp It's just right don't want touch that one , it's quiet and clean and pretty loud. I like those 6AQ5 tubes. I've got 3 amps I like the way they are , 1 that's kind of a screamer , and that poor Japanese which will probably end up in the Esteban as that Skylark in the other thread lol.
Maybe a Verb o Champ will be possible. With the VM714 Iron ? All I need is a tank :icon_biggrin:
The Silvertone 7072 a Vibro Champ?
The size of these OT's has been a bit of a mystery to me. The one in my 6AQ5 amp is the same size as a Champ OT Which is the same size as the 7072? The only one I've ever got warm is that Japanese OT which is the same size as a champ OT.
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> my council is to connect the 6.3v to the secondary
Yes, though that leads to HIGH voltage on an OT primary.
In this case, the OTs were never designed for 6V at the secondary. 6V^/4r is 10 Watts, and these are couple-Watt transformers. And 50/60Hz is probably "low" for them. The measurements may be corrupted by transformer distortion.
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Thanks for the advice PRR
Which is your council for this small transformers ?
Thanks
Franco
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I found this on eBay (http://www.ebay.com/itm/162385556809 (http://www.ebay.com/itm/162385556809) Olson SC-5f / TT-450 1 - 140VAC 5 Amp Auto Transformer Tested Working)
I was thinking what I could string together to get 1volt ac and thought ....... that never works out to be a bargain. Hopefully this will work. :dontknow:
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If you want a low voltage and don't have a variac, you can use cascaded transformers
120 / 12 > 120 / 12 you have an output around 1.2v
of course other values can be used to obtain an output around 1v
I apologize about the suggestion to connect the 6.3v to the secondaries, I didn't considered the small size of the transformer
Franco
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No apology necessary :smiley:
Everyone here has been so helpful and I don't want to impose on our friendship. I'm having a blast with these amplifiers. I'm sure the next old tape machine I find at the thrift store will be coming home with me. I hope I'm not abusing this thread.
The new VOM has a 4volt range so I should be able to get a reading using the methods demonstrated in this video. https://www.youtube.com/watch?v=Yzo3A-NywSs&t=3s (https://www.youtube.com/watch?v=Yzo3A-NywSs&t=3s)
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I don't have a scanner and thought I should share some manufacturer specs on these transformers.
Power transformer for VM-714 used in 750A, 711A
Part # 12558 manufacturer 524839 (on my part)
Pri 117vac .57A
Sec1 720vct .060A
Sec2 5vac 1.8A
Sec3 6.3vac 1.3A
Sec4 6.3vac 1.A
They do not show other replacement PT's
Output transformer fo VM-714 used in 710A, 711A
Part # 12559-1 manufacturer 138852 (on my part)
Pri 5300 ohm
Sec
30 ohm
tap
@ 8 ohm
Replacement parts: Halldorson Z1006 , Merit A-2902 , Ram AU-600 , Stancor A-3849 , Thordason 24S64 , Triad S-55Z
I'm not sure how to interpret that but will update this as soon as my Variac arrives.
That's the way it appears on the parts list. Whether the 30 ohm is the tap or the 8 ohm is the tap. Just learning here so bear with. The following is from the VM-714 manual ....
Power output:
10 watts. Less than 3% distortion at 3db below rated output.Impedance: 8 ohms. Dampening factor: 12.
Output jacks(two)
External Amp. Constant 1 volt output at 10000 ohms from normal tape level.
External Spkr. (dual position) 8 to 16 ohms impedance for single or multiple speakers (may also be used to drive a 600 ohm line: no load necessary) up to 8 volts output at less than 1% distortion.
In summary. These transformers came from a nice tape deck , the amp had frequency response 20-25000 Hz. Just guessing but the OT is worth much more than I paid for it. The list of replacement output transformers should help somebody in identifying the specs of their finds. I know I will search for those on the eBay :icon_biggrin: Thank you to all again for helping me , having a blast with this new to me hobby.
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> Whether the 30 ohm is the tap or the 8 ohm is the tap.
"Tap" is always the lower voltage/impedance connection.
LOOK at how this OT is used in the original. The "8" goes to speaker. The "30" actually goes up the 6V6 Cathode. This is NFB. This is why (for undistorted signals) the output does not care 8, 16, or 600 Ohms (or no load). The NFB keeps the output level nearly constant.
The "10 Watts" figure is optimistic. They run the 6V6 near 13W Pdiss. However the happy-load for 360V and 37mA is 10K, not 5K. They are forcing huge bias-shift in the max-output test condition. It may really deliver near 8V on 8 Ohms. We usually let SE amps bias shift but this is extreme. Especially since this is not really a "fixed bias" amp. "-20V" is derived from R25 which is flowing mostly 6V6 current, and will change at maximum output.
Figuring 6W out on a nominal 30 Ohm winding we have almost 14Vrms or 20V peak. The bias on the 6V6 is 20V (the "18V" is meter-loaded), and so there is 6dB NFB. Not a lot. Would be a fine guitar amp just the way it is. However the signal at the 6V6 grid now must be 40V peak. V2b is working hard. V2a adds more gain and then R12 turns that into significant NFB. Sensitivity at V2a grid is near 0.2V.
OMG. Not only "stereo", but Stack/Stagger stereo (on some models).
You have a Germanium diode in there.
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It would have been nice to have gotten the whole 714 deck intact :wink:
Well it looks like another oddball PT for the too high voltage too low mA pile lol. I was hoping to build a Champ with reverb. Perhaps another OT and that would work. The 714 OT would be good in that Silvertone 7072 saving its tiny OT for another 6AQ5 amp. I really like that 6AQ5 amp.
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Ciao Frankenxtein
Well it looks like another oddball PT for the too high voltage too low mA pile lol
Give a look to the transformer on this thread (that I recovered and is still waiting for a use :think1: )
http://el34world.com/Forum/index.php?topic=16097.msg157174#msg157174 (http://el34world.com/Forum/index.php?topic=16097.msg157174#msg157174)
Secondary
6.3v @ 1.8A
6.3v @ 0.9A
5v @ 2A
750v CT @ 50mA AC (375v-0-375v)
375v * 1.4 = 525v DC, not a low voltage as B+ and there is "only" 50mA AC current disposable
Franco
Post Merged
Phil, I'm not able to understand how this mod can operate :w2: :w2: :dontknow: :dontknow: :w2: :w2:
To me seems an odd schematic :w2: :w2:
(http://el34world.com/Forum/index.php?action=dlattach;topic=19355.0;attach=63800;image)
give a look to the different approach of our friend Leevi
(http://el34world.com/Forum/index.php?action=dlattach;topic=21602.0;attach=63771;image)
Leevi's mod to me has sense (and is full performing for sure)
Franco
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Ciao PhilWell it looks like another oddball PT for the too high voltage too low mA pile lol
Give a look to the transformer on this thread (that I recovered and is still waiting for a use :think1: )
http://el34world.com/Forum/index.php?topic=16097.msg157174#msg157174 (http://el34world.com/Forum/index.php?topic=16097.msg157174#msg157174)
Secondary
6.3v @ 1.8A
6.3v @ 0.9A
5v @ 2A
750v CT @ 50mA AC (375v-0-375v)
375v * 1.4 = 525v DC, not a low voltage as B+ and there is "only" 50mA AC current disposable
Franco
Post Merged
Phil, I'm not able to understand how this mod can operate :w2: :w2: :dontknow: :dontknow: :w2: :w2:
To me seems an odd schematic :w2: :w2:
(http://el34world.com/Forum/index.php?action=dlattach;topic=19355.0;attach=63800;image)
give a look to the different approach of our friend Leevi
(http://el34world.com/Forum/index.php?action=dlattach;topic=21602.0;attach=63771;image)
Leevi's mod to me has sense (and is full performing for sure)
Franco
Wow and I thought I had troubles :laugh:
I'm not sure what they have going on Down Under with that Champ Reverb (@ Offset Guitars)
Can't see the library , waiting for registration ..... to be activated. That OT listed on his print is a 7k -3.2 ohm 125A3A3 Maybe a 8 ohm load ? That's a revised version of what he started with. Pretty stuff.
If I use a 6L6, 6L6G, 6L6GB, 6L6WGA/5932 and one Preamp tube and a custom built 8k or 10k OT I'd get pretty close. to a Champ?
http://thesubjectmatter.com/calcptcurrent.html (http://thesubjectmatter.com/calcptcurrent.html)
Selected transformer voltage: 325-0-325 ( 330-0-330 mine )
Calculated voltage at first capacitor (B+): 406.25V. Subtract 6V, if using choke.
Calculated filament current (typically the 6.3v secondary): 1.23A
Calculated current: 59.37mA at 8686R calculated load (10% plus factored in). Preamp valves current draw is estimated at typical 12AX7 max dissipation of 1.2W at 330V, i.e. 3.6mA per triode
That's kind of getting away from the "thrifty"
Well the shelf is looking good for this PT :BangHead:
I have to buy a tube anyhow?
That 807 is interesting I can get that Tube , socket , cap for about $25
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I can get 1625 tube (till few mounts ago) for 5€ each, may be socket for 3.50 or 4.00 € and Topcap for 1.50 - 2.00 € don't remember well
there is less request for the 1625 tube (is a military version of 807) because it has 12.6V windings
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About the Reverb Champ, I've read the original thread, also the author don't know why it works (he says it works ..... ?????)
http://www.offsetguitars.com/forums/viewtopic.php?t=35226 (http://www.offsetguitars.com/forums/viewtopic.php?t=35226)
I prefer a lot Leevi's version
Franco
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I'm looking at the few options I have with that 714 PT. I don't understand enough of this stuff to experiment around too much. I'm reading quite a bit. I'll build something one day with it. I've got stuff to build a breadboard and I'll have a Variac soon. My limited knowledge has me trying to build simple stuff. Compared to the other OT's I have around here that 714's looks big. The custom made OT's run $30 + shipping. Which is probably not bad considering , I don't have a 5Y3 yet lol. I'll be checking out some of the transformers I have around here. Re working a few of these hack jobs I've built.
PS: Ready to start a thread for the VM714 .... seems I found my stuff here :icon_biggrin: http://el34world.com/Forum/index.php?topic=9444.msg86674#msg86674 (http://el34world.com/Forum/index.php?topic=9444.msg86674#msg86674)
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Crap? Maybe Concord RxR heavy as hell.... Barely see tubes.....24-5 bucks chance at salvation/goodwill..........2 bugle boy/mullard 12at7 & 2 of that popular tube people make headphone amps from.....6c7 or something like that. Can't remember exactly which maker of pre amp tube, but know for sure couple of my good stash came from that. Might've been Telefunken's. Point=they were pristine.
Bonus was markings were untouched, guess owing to fact you really had to disassemble, and crowbar your way in. Seems guitar players always ohing & ahing the chalky amperex markings right off the tube. CC R's were close tol.
Multi tier, multi tap switches, tons of metal, even cast frame little 5's.....looked like cute tiny EV's or JBL minis. Not high power, but simply adorable (that's attempt at humor). & you can make single 12" cab out of huge cabinet. Nice heavy metal handle too, although not beneficial for setting head on. ....who cares, it cost 25 bucks
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Crap? Maybe Concord RxR heavy as hell.... Barely see tubes.....24-5 bucks chance at salvation/goodwill..........2 bugle boy/mullard 12at7 & 2 of that popular tube people make headphone amps from.....6c7 or something like that. Can't remember exactly which maker of pre amp tube, but know for sure couple of my good stash came from that. Might've been Telefunken's. Point=they were pristine.
Bonus was markings were untouched, guess owing to fact you really had to disassemble, and crowbar your way in. Seems guitar players always ohing & ahing the chalky amperex markings right off the tube. CC R's were close tol.
Multi tier, multi tap switches, tons of metal, even cast frame little 5's.....looked like cute tiny EV's or JBL minis. Not high power, but simply adorable (that's attempt at humor). & you can make single 12" cab out of huge cabinet. Nice heavy metal handle too, although not beneficial for setting head on. ....who cares, it cost 25 bucks
The 1/4" jacks in the Silvertone 7072 I got for $15 would cost over what I paid.
Really nice parts sounds like a good score for you. I've yet to find any good speakers , the tubes I have been setting them aside. I need to make an appointment or drop them off to be tested. After I build with some not so rare tubes I have put back the original tubes just to see what they sound like. All three of them :l2: Usually it's 12AX7-6aq5 or 6bq5-6x4 and that's fine for me. After I finish my Voice of Frankenxtein. I plan on building an amp with 4 tubes :icon_biggrin:
Building from these old machines is more expensive sometimes than buying new parts. It's a heck of a lot harder finding designs other than the original to build with the really high voltages of the PT's . The OT's are usually small sub 5watt with weird wiring , color codes that change from model to model. Then it's all baked in a tiny box ........ if it's well used , I'd imagine the parts are pretty stressed. $10-15 for a Photofact on top of it. It's cheaper to build with new small iron unless you get the donor really cheap. I have yet to run out of old crap.
Hunting certain machines for certain things that you can get specs for , not just schematics. It's challenging , frustrating and fun. None of this is lost on the eBay sellers , trying to make a killing in antique tape recorders. I scan thru there from time to time and find a bargain. lol .....
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OMG. Not only "stereo", but Stack/Stagger stereo (on some models).
?? What is "Stack/Stagger stereo"?
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This info from... http://www.thevoiceofmusic.com/faq_restoration.html#tapeFAQ (http://www.thevoiceofmusic.com/faq_restoration.html#tapeFAQ)
Q7-5: I have a switch on my V-M tape recorder with two positions called “Stacked” and “Staggered”. What does it do?
A7-5: First, a little history. The very first stereo format was on reel to reel tape! V-M Corporation offered a conversion kit for the venerable Model 700 in 1955 - some three years before stereo records and five years before stereo FM broadcasts! The first format? Very simple - take a second half track monaural head, turn it upside down, and mount it to the right of the existing monaural head. Connect it up with another pre-amp and you have the “staggered” stereo tape format! The tapes were recorded with the starting points of the “L” and “R” tracks “staggered” so that both signals would be in sync when picked up by the playback heads. This format is also called “offset”. In 1958, as magnetic head manufacturing capabilities improved, the “stacked” or “in-line” format was invented - and remained the broadcast standard for many years - the so-called “half track stereo” format. The V-M Model 714 was a hit because it had a switch to play both the newer “stacked” and older “staggered” formats. In November of 1959, V-M brought out the Model 720, one of the first on the market to play the new “quarter track” stereo tapes.
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It's been a good day to eBay 37 is the number :icon_biggrin:
Snatched up a handful (7) NOS Single ended OT's for $37 one of them a Merit A-2930 (5k pri - 3.5ohm sec) 6 others in that lot UTC , Stancor , Thordarson , .... Tiny iron :wink: They got me looking at 6y6 tubes :think1:
Started looking for PT's and ........ well that's a trick finding lower voltage PT's but ..... I'm sure there's a couple here that would work.
Scored a $37 PT from a Stromberg Carlson SR405 Will make a nice PP amp. It ran a couple 6F6 tubes ...
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Found a nice PP OT
35:1
9800 ohm primary blue-red-brown / 8ohms green-black
about 3 + lbs
Iron Size
2.5" wide
3" tall
1-3/8" thick (1.25"minus bells)
2-7/8" bell to bell Winding's
The other side is scratched up and I can't make out any numbers
It has 161230 , under that it has a logo ? Anyone seen that logo?
It was hooked up to 2- 6L6GC's and has that marked on the top.
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350-450VDC, self-bias, aim at 25W Pdiss per 6L6CG for 450V, get 30W with hi-THD bass, aim lower and get 20W with hi-fi bass.
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Got this in a lot of transformers ? :dontknow:
TF4RX21AH
This number 863780 led me to
https://www.wbparts.com/rfq/5950-00-997-8957.html (https://www.wbparts.com/rfq/5950-00-997-8957.html)
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from 3.5 to 7KC (KHz)
The bandwidth is missing a lot, if 7Kc can be good for guitar, 3.5KC minimum is very poor
I think that transformer was used in some military telephone equipment (or similar)
I had a small stock of similar transformers and give all to a friend
Franco
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Baldwin 46H power amp minus tubes lol
Toyed with the idea to fix it but , the darn thing is so heavy.
On Platefire's PR40 thread I had mentioned building a Tri amp with my PR40 power supply and now I have one :dontknow:
It started when I was looking at the pair of 512-023628 OT's then I saw the 512-025947 that ran the bass channel in the amp.
Well I scored the whole amp for $85 w/shipping. Lots of nice wire , sockets , a choke ....... waiting for a seller to answer a question on eBay if his technical manual for the Baldwin 46H has a Schematic and or parts list. That would be if I was to restore the monster.
I'd imagine costs to build 3 amps would be darn near the same as re tubing , capping this monster.