Weber Maggie

[Guitarzan]

Hi guys,
I know it's been a long time since I've posted. Time seems to move at a different rate for me so stuff that others would have started finished and moved on by now, for me are still in the "thinking" stages. Ah well, it's health issues that I won't drag you down with. So anyway, I just thought I'd share some pics of donor for the Weber Maggie project. It's a Stromberg Carlson AU-29 that's in pretty rough shape. I intend to strip in down to the bare chassis, sand & paint, & go from there. This could take days, (doubtful) weeks, months (more likely), or even never get done. Here's the beginnings tho and I'm sure I'll be looking for support as this moves ahead. I intend to use the Maggie as the basic idea but go with all octal tubes as my first variation from the actual Maggie as put forth by Weber. Here's Weber's layout http://www.tedweber.com/media/kits/maggie_layout.jpg and schematic http://www.tedweber.com/media/kits/maggie_schem.jpg for your review.


Here's the donor amp and a gutshot.

[llama]

That is in rough shape, but I've been in worse.  If you just keep at it, little by little, it will get done, eventually.  I'd love to move faster at these things too, but Life (wife) is an impedance.

I look fwd to seeing any progress as you post.

-Scot

[PRR]

Hey! My amp only goes to "11". Yours goes to "100"!!! YOWSA!

[DummyLoad]

Hey! My amp only goes to "11". Yours goes to "100"!!! YOWSA!

that'll be 1001.01 clams extra thankuveddymuch!

[DummyLoad]

PT looks damaged GZ.      ...at the very least it got really hot.

[tubeswell]

What Dummyload said - test the PT on a variac or with a dimmer lamp

[sluckey]

And be careful with those green filament leads. I'm pretty sure those wires are the actual winding extending beyond the shell and spaghetti just slipped over them. That was common during that time period. They will break easier than stranded wire.

[Guitarzan]

PT looks damaged GZ.      ...at the very least it got really hot.

It also smells like burned transformer. Good eye but for suspecting, but the nose knows. Even Jane & the money noticed it when they walked by wile I was disturbing things insider there. Jane said "Smells like a burning motor" the monkey grunted in agreement

[Guitarzan]

Based on the "frozen" black drops that are coming out it, the awful smell, and burnt looking paint & wires, I'm calling it toast. However, there have been a couple of suggestions posted here for testing it and I was wondering, wouldn't it be ok to simply secure it and the wires on the bench, apply 120 volts to the primary and measure the output (if any) on the secondaries with a meter? You may have noticed the Variac in the background of the donor picture, but is there any reason to actually use it in this case and apply any kind of load to the secondaries? I've tested transformers in this way in my past life as an HVAC serviceman. Was I risking burning the thing out by just using this shortcut? I'm not all that when it comes to audio equipment but I am comfortable around all sorts of electricity. I've worked on everything from low voltage control systems to 460v industrial buss ducts so I know how to handle electricity.

[sluckey]

wouldn't it be ok to simply secure it and the wires on the bench, apply 120 volts to the primary and measure the output (if any) on the secondaries with a meter?

Yes. I wouldn't call it dead based on looks only. But I would just pull all tubes and check it right in the chassis. All wires are tacked down and there's no possibility of wires shorting. I would use the variac and start with a low voltage and then bring it up to 120VAC if no sign of smoke. I'd put a 2A fuse in the variac if the amp has no fuse.

[Willabe]

I've tested transformers in this way in my past life as an HVAC serviceman. Was I risking burning the thing out by just using this shortcut? I'm not all that when it comes to audio equipment but I am comfortable around all sorts of electricity. I've worked on everything from low voltage control systems to 460v industrial buss ducts so I know how to handle electricity.

A PT is a PT, it 'trans forms' electrical power, voltage/current. It has a primary and a secondary, maybe a number of primaries and secondaries.

It either steps up the voltage or steps down the voltage, sometimes it does both with different secondary winds, like in a guitar amp PT.

A PT doesn't know what it is being used in and it doesn't care, as long as you don't exceed it's voltage and current ratings. 


                         Brad   

[Guitarzan]

That's what I figured. As long as I don't have stuff flopping around so it can touch each other or anything else, and use the appropriate voltage on the primary, if nothing is hooked up it should just sit there a "coast" making the correct secondary voltages without even breathing hard. I just got in out and the wires are all toasted and it reeks. Moving the wires around made much of the crunchy insulation fall off and stirred up the smell to where the whole basement smells like a fluorescent lamp ballast just fried down there. It's dead and that's fine. I have a tranny that can go right in there.

[Guitarzan]

Getting close to a clean canvas now. Just for fun I cleaned this up and thought you might get a hoot outta seeing it.
Too bad the whole thing couldn't have remained original and in this kind of condition.
Sorry about the picture not being very clear, but out of several tries this was the best I could do.

[Guitarzan]

So what do you know? The chassis seems to be copper plated. Here's the platform on which I will be building.
I was thinking of using some of that hammered looking spray paint for this unless someone has a better idea.

[heresrobert]

I once sprayed a faceplate for a tweed type amp with a Rustoleum hammered bronze paint. I thought it came out very good. Just make sure your metal is well prepped. I'll try to snap a picture this evening and post it.

Robert

[PRR]

Tar coming out of a transformer is not *proof* it has been cooked. Some factories were just too generous with the soup.

In any case, transformer that old should be brought-up gingerly in-case it has become just a heavy short or a smoke-bomb.

The burnt-motor smell *may* be just super-old varnish, but does suggest something has gone bad. But a burnt OT smells the same as a burnt PT and is almost as likely to smoke. (Especially if the last owner was whipping it hard without a load.)

[Guitarzan]

Tar coming out of a transformer is not *proof* it has been cooked. Some factories were just too generous with the soup.

In any case, transformer that old should be brought-up gingerly in-case it has become just a heavy short or a smoke-bomb.

The burnt-motor smell *may* be just super-old varnish, but does suggest something has gone bad. But a burnt OT smells the same as a burnt PT and is almost as likely to smoke. (Especially if the last owner was whipping it hard without a load.)

Points well taken and appreciated. I may just do test the resistance on the various windings the next time I have the meter out to verify whether any are open or shorted. I have a procedure copied and saved someplace around here that lays out how you can tell the difference between the primary, HV and heater windings by the amount of resistance they show on a meter. I'd probably go that route before applying power to it anyway. Then of course your point about it being a potential smoke bomb is an excellent reason to bring it up with a Variac.
Thanks very much for the valuable tips!


Well, I got the inside of the thing cleaned up the best I could. It's tough reaching into every corner of the inside of a small box like that.  So it's as good as it's gonna get. I wiped it all down with some paint thinner & then some rubbing alcohol just to make sure it's clean and got a 1st coat of Rustoleum brand Hammerite on it too. I settled on a bronze color that's a little on the dark side. Darker I think than the color on the cap but it is what it is now. While that's drying I'm gonna look for the caps, get the tube sockets and other stuff together as well. When progress warrants, I'll post some new pix.

[Guitarzan]

Tar coming out of a transformer is not *proof* it has been cooked. Some factories were just too generous with the soup.

In any case, transformer that old should be brought-up gingerly in-case it has become just a heavy short or a smoke-bomb.

The burnt-motor smell *may* be just super-old varnish, but does suggest something has gone bad. But a burnt OT smells the same as a burnt PT and is almost as likely to smoke. (Especially if the last owner was whipping it hard without a load.)

Hi guys.
After taking these points into consideration and a closer look at the P.T. I decided it was worth testing to see whether the transformer's shot or not. I remembered seeing this at some point in the past and looked it up again to use it as a guide to do some preliminary testing. I figured that if any of the windings were either open or shorted to the case I could easily determine it with a meter and could also verify the various windings with the readings the Radio Museum suggested I should be seeing in the char shown in that link. BTW, unlike the hypothetical xfrmr in their example,  my wires can still be identified by their color code after a little cleaning.


So, my DMM tells me that I'm seeing the correct resistance everywhere according to the Radio Museum's procedure but I still have a couple of questions before I apply voltage to the primary in order to test the secondaries for correct values.


First of all, PRR says the transformer should be brought up "gingerly" in case it's a smoke bomb waiting to be lit. So I can connect the primary side to my variac but just exactly is the definition of "gingerly"? do I crank the variac all the down to zero and start from there? Can I do any damage to thing by applying to little voltage? My guess is no, but there's no point in guessing since you guys are always so generous with the knowledge and experience so that's a good part of why I'm here in the first place. Obviously when I apply the primary voltage it'll be with no load and all of the other wires safely segregated so I can get a reading from them with my meter. Just how slowly do I need to crank the variac up to 100% so I can test all of the secondary voltages?


Next, the reds are the High Voltage and the Green & Yellow the center tap. The Yellows are the heaters for the 5Y3 and Greens are the heaters for the rest of the tubes, right? So what is that curled up green one with 2 wires inside of the one green jacket?


Also, I don't think it matters but the primary wires are both black so there's no "Hot & Neutral" between them, correct? It doesn't matter which is which, or does it?


I am including pictures of the xfrmr in addition to the progress so far which isn't an awful lot but you guys know it takes me a great deal of time to plug away at these sorts of things because of my health issues. So being an "instant gratification" sort myself, I apologize to those who wish they'd see more getting done, and a whole lot faster, but I do what I can when I can and this is it for now.

[Willabe]

The chassis looks great! I wouldn't have the patience to do such a nice job.   

Yes, the green pair/yellow pair of wires are probably the heaters for tubes (green) and rectifier (yellow).

The 2nd pair of green wires in the green sleeve might be another pair of tube heaters? I'd take a resistance reading on them and see. Also take a resistance reading from 1 of those green wires to each of the other wires 1 at a time to make sure their isolated from every thing else. I think they may have put that sleeve on them just to pair them up from the other green pair?

The variac, yes start with 0 and bring it up slowly (~ 20 to 30 seconds from 0 to full 120acv?), listen, look and smell for signs of trouble. Maybe best to use the light bulb limiter in between the variac and the PT for the test. (Yes the PT has no load on it but if there's an internal short that's as big a load as you can get, +acv straight to ground.    )

If it passes the light bulb limiter test, then try it with out the limiter. I'd still use the variac and bring it up slowly.

If/when it passes the 2nd test, then using your meter with alligator clips, disconnecting the PT from the wall acv each time before moving the clips for the next pair, and making sure the other PT fly leads are secured and securely taped or wire nutted off, take acv readings from each pair with the PT getting the full 120acv wall voltage.

If it looks like any of the cloth covered wires where they come out of the end bell housing are worn, then see if you can slide a piece of shrink wrap over the worn part.

                   Brad     

[Guitarzan]

I was so encouraged by the initial testing that I went ahead and cleaned it up and painted it before verifying for sure that's gonna work. Now it'll prolly go up in flames as soon as I apply power to it.    sorta like washing the car having anything to do with making it rain. Well, I'm not that superstitious. I have an old ext cord that has insulated gator clips in place of the female end. In my former life as an HVAC serviceman I used to use it for bench testing motors and all sorts of stuff. I was thinking of taking a small piece of wood like a short 1 X 2 and putting a series of small nails in it to wrap each of the secondary wires around. That oughtta keep 'em in place and make metering them out a cinch.


As for those 2 extra greens, I still don't know what those are but I don't think they were ever used. I didn't cut them loose when I took the thing apart. That was just coiled up to keep it outta the way. When you look inside of the end of it, there are 2 bare, or lacquer coated wires inside of it. It's not like another pair of greens as the greens have their own separate green jackets. Again I really don't know what heck they are. I was thinking maybe it was a ground? I'm headed downstairs to giver 'er the old smoke test now. If I ever was trying to jinx myself, I'm doing it now eh? Painting it and saying "smoke" test? Good thing I'm not superstitious.


I'll get pics of this next bit of progress while I'm at it. That is if progress is actually made.

[Willabe]

I was so encouraged by the initial testing that I went ahead and cleaned it up and painted it before verifying for sure that's gonna work. Now it'll prolly go up in flames as soon as I apply power to it.    sorta like washing the car having anything to do with making it rain.

Naw. 

I have an old ext cord that has insulated gator clips in place of the female end. In my former life as an HVAC serviceman I used to use it for bench testing motors and all sorts of stuff.

Well, I meant insulated gator clips for/on your meter probes but that ext. cord should work for the PT's primary.

I was thinking of taking a small piece of wood like a short 1 X 2 and putting a series of small nails in it to wrap each of the secondary wires around. That oughtta keep 'em in place and make metering them out a cinch.

That should work great, I'd try down the 2 primary leads too, the same way. Maybe use small plastic zip tye's to hold the fly leads to the nails?


                       Brad     

[Willabe]

As for those 2 extra greens, I still don't know what those are but I don't think they were ever used. I didn't cut them loose when I took the thing apart. That was just coiled up to keep it outta the way. When you look inside of the end of it, there are 2 bare, or lacquer coated wires inside of it. It's not like another pair of greens as the greens have their own separate green jackets.

I don't know what they are either, ohm test them (resistance) with your meter. It sounds like their the actual PT wind wire brought in a sleeve.


                    Brad   

[Guitarzan]

Well here's a picture of the rig I came up with to do my testing. I went down there with intention of doing as I said in earlier post but saw this 5F1 turret board laying there and the light bulb slowly on over my thick head. I just lengthened the wires that were too short to use comfortably, stripped the ends long enough to reach thru the turrets and bend over to secure, put them in pairs and brought it up slowly with the Variac to 130 volts. My DMM isn't the best for voltage reading as it has only on scale and that's 600V so I'm not getting the 00.0 that I'd like to see, but here's the poop.
It's a Stancor PM-8409, whether that's an OEM # or not I do not know.
Greens came at 6 volts
Yellows were 5 volts
The HVs were 820
HVCT 410 and 411
That double wire in the green jacket seems to be a CT for the greens. Anyway it acts like it. I got 3 volts to one leg and 2 to the other. If I could get more accurate readings it would make me feel much better and I'll bet that the Greens to that CT if that's what it is would actually be reading 3.something on each leg.
Actually, I have a Sams Photofact thingy on the Stromberg Carlson AU-29 around here someplace. I'll have to dig for that and see if it tells me what double green one is.
So here's what it's shaping up to look like so far.

[Willabe]

Test rig worked good.   

Do you know what the power tubes were in that amp?

[Guitarzan]

Test rig worked good.   

Do you know what the power tubes were in that amp?

Yeah man! It worked like a charm. Every once in a while I come up with a pretty decent idea. On the other hand, there's a very old saying...
"Give the hardest job to the laziest man and he'll find the easiest way to get it done."
I found the Sams on that thing. It was originally a SE 10 watt amp with 2 inputs, phono and mic.
it had 2 6SJ7 tubes in the 2 inputs, a 6L6 for the power tube and a 5Y3 rectifier.
The Sams says tube types, "6SJ7 Phono Pre-Amp 6SJ7 AF Amp." What do they mean by AF? do you know?
Here's a shot of the back page of the Sams. I hope you can make it out OK. It's really the only way I have to post it here. I don't have a scanner.

[sluckey]

AF = Audio Frequency

[Guitarzan]

Thanks. Y'know what tho? It doesn't seem to show the mystery wire(s) tho

[sluckey]

Thanks. Y'know what tho? It doesn't seem to show the mystery wire(s) tho

The mystery wires are your filament windings. The two wires that are inside that one green insulation sleeve are actually the ends of the other two green wires. Long ago it was common for a centertapped filament transformer to actually consist of two separate windings. Each winding is just a coil of wire with a beginning and an end, ie, two wires coming out of the transformer. This makes for a total of 4 wires. The wires you see are actually the same wire that makes up the winding. Two wires would be connected together such that the two windings are connected in series aiding so the voltages add (kinda like two flashlight batteries connected in series aiding). The two wires that are inside that one insulation sleeve need to actually be soldered together for a reliable operation. Those wires are actually insulated with a thin coat of varnish, just like any magnet or motor wire. You may have to scrape the varnish off the ends of the wires to get a good connection. Once the wires are soldered together, just treat them as a standard center tap for the filaments.

[Guitarzan]

Well that makes sense and also explains why I said in an earlier post that it acts like a center tap for the green pair but that my reading wasn't dead center 3v from each leg like the HVCT was. HV reading was 820 and the to the CT it was 410 and 411. I attributed this to a deficiency in the meter I was using, but the reading was actually fluctuating and took a while to settle in at the 3 on one leg and 2 on the other. The 2 was blinking back and forth between 1 & 2 on the LCD display for a lot longer than it took to read any of the other windings & I finally settled on it being 2 or reckoned that since my meter doesn't read that voltage in anything to the right of 0, that it was prolly 1.8 or something. My meter simply has a 600v range and reads from 0 - 600 with no decimal point.
Now I'm thinking that it was just a function of the way the point of the meter probe was making contact between those two lacquered wires. Remember, I had the ends exposed far enough to reach thru the turret, then bend over to secure. So as I took each reading I backed off, wrote it down then went in for another reading.


So being the inexperience sort that I am, I have not seen a center tapped filament winding like this before. Is it common? How/why is it used?

[sluckey]

it acts like a center tap for the green pair but that my reading wasn't dead center 3v from each leg

Hopefully when you solder the two wires together the reading will be close to dead center.

I have not seen a center tapped filament winding like this before. Is it common? How/why is it used?

Having a center tap is very common. The center tap is used to reduce filament hum. It's commonly connected to chassis ground.

It's no longer common to bring the actual solid core filament wires outside the shell of the PT. Usual practice today is to solder stranded conductors to the actual solid wires inside the PT shell. The stranded wires are more flexible and user friendly.

[Guitarzan]

So the CT for the HV windings should go to the chassis ground as shown in the original Stromberg Carlson shcematic, and the filament CT should go to the very same grounding lug?
Just out of curiosity, why do you suppose the yellow pair doesn't have a similar setup with 2 wires inside of a yellow jacket? The greens have a CT, the reds have one that's made like you mention with a stranded wire coming out of the shell rather than the solids sharing a jacket like the greens, but the yellows don't have one.
  I'll guess at the answer just to show either I have a basic grasp of this concept or just how stupid I am, particularly for taking a stab at the answer in front of a bunch of guys who really know their stuff. It's because the yellow pair are for the rectifier tube right? And since it's not a signal handling tube, it won't cause the filament hum that the other tubes can?

[sluckey]

Just out of curiosity, why do you suppose the yellow pair doesn't have a similar setup with 2 wires inside of a yellow jacket?

Some real old stuff did have a centertap on the yellow pair. But you would never connect it to ground! There's B+ on the filaments of most of the 5V rectifier tubes!

[Guitarzan]

  SEE?!?? I knew taking a stab at that answer was a bad idea!
Thanks for straightening me out on that one.
BTW, none of that stuff that I put in the chassis so far is not in there permanently. It's more less just sitting there for the purpose of getting the picture for the BB members. I still want to make a small eyelet board that will basically replace the Maggie board from Weber, from just to the right of the filter caps on down to where the 2 "boost" caps and the 1.5k resistor are. I can sort of squeeze that stuff closer together than they are showing it, right? Plus I have the multi-section can for the filter caps. So once I get that made up I can decide the best way to orient the tube sockets and that cap can with my little eyelet board in there.
Here's their layout again for convenience sake.

[Guitarzan]

Well, there were burnt wires, burnt resistors, and caps that were basically empty with the paper loose and unwrapped as if you rolled a piece of paper into a tube just once and let it try to go back to being flat on its own. So I suppose that burnt transformer smell could have come from any of that stuff. Burnt electronic smell probably smells pretty much the same regardless of which of the components actually cooked.


Then there's the output transformer. It looks fine, but I know that doesn't mean it's still good. The other side of that coin is, was it EVER any good? Do any of you guys have any experience with these (SC amps) things? I think the PT was a replacement based on what the SAMS says the specs are supposed to be versus what I actually observed. The Sams says the HV sec. should be 680 volts and I got 820. It also shows a Stromberg Carlson part # and has blank fields where the Stancor, Merit, & Chicago replacement part #s should go. These are the clues that lead me to believe its not factory. I'm certain I could be wrong about that too but getting back to the OT.


There were ink-stamped numbers on the frame but they're mostly gone. I can sort of make out what I believe is 39643 which is the top or 1st number. Under that it looks as though there was a smaller font sized upper case "A" followed by larger font sized 1??X?0 The "X" is either a 3,8, or 6.
I don't know if testing the resistance in the various windings is of any value but since it was a simple early test for the PT I went ahead and got some readings which are as follows:
Pri. 153 ohms
Secondaries to the common wire
4-ohm tap, 1.6 ohms
8-ohm tap, 2.3
16-ohm tap, 1.9


None of the wires showed any continuity to the case.


I wonder if anyone knows whether This amp had a good OT in it from the start? Do I bother trusting it to the point of going any further with testing it? It's a good distance off yet before I'll actually get to the point of needing it so there's no rush on getting it squared away. The one Weber sells for the Maggie is $37.00. ClassicTone has a Single Ended 15 Watt unit for $30.00 and I've used their stuff and been satisfied with it.


Any information, opinions on this subject or anything to do with this project, as always, are very much appreciated.


-dale

[Guitarzan]

Nothing on the O.T. eh? Well, that's okay, It's quite a ways off yet before I'm actually going to need that. Plus thanks to Sluckey encouraging me to actually confirm the condition of the P.T., I can keep the replacement one I was thinking of putting in there on the shelf for a future project and with that money in bank, I could justify buying a new O.T.
 
 
I do have another question tho. As I mentioned in a previous post, I was thinking about making up a little board to hold everything to the right of the filter caps, starting with the 460 ohm 10 watt resistor. Actually what I have handy is a 500 ohm Dale that I intend to use there. But my little board was going to be from that resistor to right as you look at it in the layout. I'm using the layout provided by Weber as a guide. I have a multi-section cap can to do the filter caps with and plenty of room in the chassis for a small eyelet board but here's the thing I haven't mentioned yet. I was thinking of using 2 different preamp tubes, and wire one of them to an input just straight forward without any bell or whistles, and then the other one will be wired up with the 3-way switch. So I was wondering what the plain input preamp tube might be. What suggestions you guys might have for a favorite sounding octal based tube that's NOT a 6SL7 because that was my plan for the preamp tube in the part of Weber's Maggie circuit that I am using. So I guess I was thinking that if the 6SL7 is an octal equivalent to the 12AX7, then something with a little lighter amplification factor or whatever the proper terminology is for the "strength" or "power" of the tube. Maybe like 12AU7 in an octal form or something like that. I'd like to hear opinions on a nice warm tube that will maybe make a better "bedroom" input for this amp.
 
 
Also, the cap can has the 25uf @ 50 v section to use as the cathode bypass cap for the 6L6. I think I read once someplace that this is not an ideal setup so I'm wondering if that's actually the case. If so, I can put a separate bypass cap in for the 6L6 and simply not use that section on the can. If it's not an issue tho, I'd just as soon use the one in the can since it's there.
 
 
Here's a sketch of the little eyelet board I'm planning. it does not include the second preamp tube components and I may need some help in just how to add those parts to this layout. Any help in that regard is also going to be very much appreciated.
 
 
Please and thanks as always, and I'll be looking forward to any replies.

[sluckey]

Nothing on the O.T. eh?

It's probably fine. Did your donor amp use a 6L6? If so, I'd use that OT. Just keep an eye on it when you fire it up.

Maybe like 12AU7 in an octal form or something like that.

6SN7

Also, the cap can has the 25uf @ 50 v section to use as the cathode bypass cap for the 6L6.

That was very common in consumer audio 50 years ago. But, unless you have recently bought that can new I would toss it. I would not trust that cap can if it was pulled from another chassis, or even if I bought it brand new 30 years ago and never used it. E-caps will dry up just as fast sitting in a parts bin as they will installed on a chassis.

Here's a sketch of the little eyelet board I'm planning.

Should work just fine.

[Guitarzan]

Thanks man!
Sluckey, you're the man! You've really helped me  lot on this and I appreciate it. Yes I bought the cap can recently. Maybe 6 months ago. I got from a guy on eBay who has 100% feedback rating and seemed to me to be a reputable seller. He sold it as new. So I certainly hope it's good. I plan of course to bring the amp up slowly on the variac when I fire it up the first time. I also have the light bulb-in-series device that build on a board quite a few years ago, but kept my eye open for a decent variac at good price and after a couple of years finally got one.


So that cap can, assuming it's good, is ok to use? I mean the low voltage section. There's nothing wrong with having the 6L6's cathode bypass cap sharing the same can as the filter caps? I knew I read someplace that someone on one of the forums thought that setup was terrible. So I searched for it last night and found the thread on another forum. The guy had an AU-29 that he simply wanted to get running. It had a bad hum and he was looking for troubleshooting advice. He posted a schematic and one of the replies was that some guy hated the fact that the 25uf 50v cap shared the same can as the filter caps. He doesn't explain why he hates it but just tells the other guy to put an individual one in. Then he goes on to suggest the guy should toss the whole can replace it with individual caps.


I can see it if the filter caps are bad and you can't find of of the correct value(s) anymore, but in the end, if I'm remembering correctly, the original guy did replace some stuff including the 6L6 bypass cap, but not the whole can.

[sluckey]

The can has a lot of stuff written on it. Post all that info. If you don't want to write it all down then post a hi rez pic so we can see everything written on the can. Maybe there's a date code on the can. That's what is really important. The important question is when was the can manufactured.

New production twist tab cans are EXPENSIVE. If you didn't pay $30-$40 for that can, it's probably quite old.

There is no problem using a bypass cap that's built into the can, but with small low voltage caps being so cheap, why bother?

BTW, there is a user by the name of "gui_tarzan" on another forum I got to occasionally. Any relation to you?

[Guitarzan]

It's not me. I'm guitarzan56 on the tele discussion page. Yeah, you're right, they are ridiculously stinking cheap. I have no idea why I'm making an issue of it. Very good point. I guess it was simply to use it since it's there and save the space but even that is nothing compared to amount of room that's inside of that box. It's really a pretty good sized chassis. while the area isn't huge as you look at the top, the volume is quite large because the thing is like 3" deep!


So here's what the can says on it:
I think the only thing that may be of any help is this, UP8D102
otherwise, all it says is "20, 10, & 10 MFD. 475 WV in three lines
the 4th line says "25 MFD @ 50 WV"
under that, "Cornell-Dubilier"
under that "BY"


on the bottom there's "G" written in and ink pen by hand. I'm guessing that the seller must have the equipment to test these and that's how he hakes the claim of "New" or "Tests as new" or whatever language he used along with his 100% feedback that made me think it was probably alright. I think it was somewhere between 20 and 30 bux. from a guy whose username is lilwing3.

[Guitarzan]

Nothing on the O.T. eh?

It's probably fine. Did your donor amp use a 6L6? If so, I'd use that OT. Just keep an eye on it when you fire it up.

Maybe like 12AU7 in an octal form or something like that.

6SN7

Also, the cap can has the 25uf @ 50 v section to use as the cathode bypass cap for the 6L6.

That was very common in consumer audio 50 years ago. But, unless you have recently bought that can new I would toss it. I would not trust that cap can if it was pulled from another chassis, or even if I bought it brand new 30 years ago and never used it. E-caps will dry up just as fast sitting in a parts bin as they will installed on a chassis.

Here's a sketch of the little eyelet board I'm planning.

Should work just fine.

I will search the schematic library for an amp that uses a 6SN7 and 6L6 in a single ended config so I can get an idea of what caps and resistors to use with it, unless you know of one off the top of your head, and the location of it, to save me some searching. Otherwise, I really don't mind the search. I just thought I'd ask in case you know of one and can pinpoint it with zero effort.


The tube data sheet site I used to use seems like it had all of the tube specs listed on the sheet, plus a little diagram of an example of it being used in a circuit. I'm sure I've seen data sheets that look like that but I can't find those anymore either. At any rate, I'm going to have to come up with the values for those components to go with the 6SN7. Everyone should know, that doesn't know already, that I am not an expert at this. I'm much better with the layouts than I am with schematics. I can work off of a schematic if that's all that's available but I'm  not all that good at it. The layout diagrams are like painting by numbers so I find them much easier as a neophyte in this sort of thing. And I always appreciate everyone's kind and generous replies to my posts. You guys' generosity with your knowledge and experience is just great and I really am thankful for all the help I get when I post my projects on this board.

[shooter]

Fwiw I attached a schematic of a 6sn7 pre that I *stole* from Sluckey, tweak a little and I've had it drive 6L6, Kt88, 6550, and an EL-34  SE.  if it's played at about 1/2 max, one of the cleanest, mellow amps, past 70% and it's just way to muddy distorted for me.  It's my "default" bedroom amp.

[Guitarzan]

Fwiw I attached a schematic of a 6sn7 pre that I *stole* from Sluckey, tweak a little and I've had it drive 6L6, Kt88, 6550, and an EL-34  SE.  if it's played at about 1/2 max, one of the cleanest, mellow amps, past 70% and it's just way to muddy distorted for me.  It's my "default" bedroom amp.

Thanks very much. I'll look it over and take into serious consideration.

[Guitarzan]

Hi guys.
Assuming that I'll need to add resistors and caps for the "Clean" or "Bedroom" input that will have it's own preamp tube (a 6SN7 has been suggested) I took my sketch, redrew it on the top of this picture, and then again on the left hand side of the "broken" eyelet board on the bottom. The right piece of the "broken" board represents what I am thinking I will have to add to make it work. I don't know if this is even correct, but if it is, I still don't know the values of the caps and resistors that will reside in those spots I have depicted for them in the sketch.


Anyone feel like putting me straight on this part of it? I have the material to make a board out of, and around 100 eyelets or so. So I am actually to the point where I could get the board made up and pre-soldered and everything with either some long leads hanging off of it for when it is install time, or maybe just leave the eyelets that go to the cap can, ground, tube(s), pot(s) and so forth un-soldered until install time. That part is of course unimportant. The thing right now is that I haven't the knowledge to go any further with it unless I scrap any ideas of deviating from the Weber layout since the extent of my knowledge is pretty close to a "paint by numbers" sort of deal with these things. OK, maybe I'm a little better than painting by numbers, but not a lot. Jane and the monkey think I'm pretty smart, but you guys know better. 

[Guitarzan]

The can has a lot of stuff written on it. Post all that info. If you don't want to write it all down then post a hi rez pic so we can see everything written on the can. Maybe there's a date code on the can. That's what is really important. The important question is when was the can manufactured.

New production twist tab cans are EXPENSIVE. If you didn't pay $30-$40 for that can, it's probably quite old.

There is no problem using a bypass cap that's built into the can, but with small low voltage caps being so cheap, why bother?

BTW, there is a user by the name of "gui_tarzan" on another forum I got to occasionally. Any relation to you?

So the numbers I posted from that cap can didn't help any eh?
I figured the only part that might be of any help was that UP8D102 but I tried doing a Google search for it and nothing came up.
There's nothing else on there but the section values, and at the very bottom "BY" but that's it.

[Guitarzan]

Enormous and heartfelt apologies to Shooter, and the rest of the board for missing the fact that the schematic he posted HAS all of the cap and resistor values that I'm asking for. DUH!    Shame on me for having a senior moment there. Jane and the monkey finally noticed it when they were looking over the entire topic, and saw my little sketch minus component values on the table. "Why don't you write in the numbers from that schematic someone posted?" said Jane, with the monkey grunting in agreement.


So a new sketch of the entire layout will be posted a little later today and this time it will also have the chassis layout at it stands, with tubes, pots, and everything. We shall see if I can transfer my concept of this thing into a workable layout diagram. I think I can do it. I think deciding where exactly to put the eyelet board, along with the tub socket orientation may be the trickiest part, but we'll see.


Thanks again to Shooter and to everyone for your input.

[shooter]

Just take your time and enjoy the process, success is a well littered road of great failures

[Guitarzan]

Just take your time and enjoy the process, success is a well littered road of great failures

Great quote man, mind if I steal it?


So I printed  your schemo, and the data sheets for the 6SL7 and 6SN7 tubes as well as the Maggie layout from Weber, AND, the layout for Weber's 5E3X2. It occurred to me that it had the a very similar setup going on in which an input goes to a preamp tube and the next input to the next tube. I haven't looked at that one in a couple of years which is why it didn't come to me sooner but having a look pretty much verified that the right hand section of my "broken" eyelet board sketch is in fact pretty close to what it needs to be to work. I didn't add the connections behind the board or where the components connect to the cap can, tubes, pots, etc. I just left that part for the board to assume I'd get those things worked out and I will/have. I was just thinking about the components on the board itself and how they'll reside there. Anyway, I'm headed for the bench now. TTYGL   

[shooter]

mind if I steal it

sure, since "a good artist will borrow, but a great artist will steal" (this one's NOT mine )

[Guitarzan]

   LOL!!
Thanks man.

[lego4040]

Very cool looking project there. As a licensed HVAC mechanic myself I have been able to learn so much more in amps because of the electrical understanding needed and all the help given here