Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on September 12, 2015, 09:41:53 pm
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I am almost finished building a 1959 Tweed Bassman clone board. I have used all NOS Allen Bradley carbon comps.
For coupling and tone caps i used 1963 Good All .022 & .02 capacitors. .1 Mullard Mustard caps from a Traynor YSR1.
Surprising enough they are all dead on there rated values.
The resistors as well are in good value range. All i need is the 250 pf Molded Mica axial lead treble cap. Super hard to find but i managed and it is on the way to me.
I have a 1968 50 watt Bassman output transformer which is 4 ohm. Don't think i will hear a major difference from the original 2 ohm impedance but time will tell.
The cab is Peavey Classic 410E cab. Funny but it worked out having nearly the exact same dimensions as a tweed bassman cab.
The Peavey cab is 1/4" wider but thats it. Hopefully i will be done in the next month. All these parts are not cheap. I used Doug's yellow cloth 22 gauge wire. I have found no better wire than what Doug has.
Edit: I am scratching the use of the Peavey 410E cabinet. No sense in altering a perfectly good 410 cab. I am thinking of a Tweed Head cab like the ones a guy is selling on ebay.
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Bias
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Got Doug's yellow 22 gauge cloth wire this morning. Ordered Saturday. I didn't expect it to arrive that fast, as i ordered it over the weekend.
Well 10' of wire went fast. I was left with 1" of it. Now i need to order a little more. Surprising just how much wire it takes for a complete build.
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Looks great man. Do yourself a favor and order way more wire than you think you need as you will end up using it somewhere.
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Do yourself a favor and order way more wire than you think you need as you will end up using it somewhere.
Exactly what i have been thinking the last 4 days. 100' of each color should last me for some time. Not to mention that if Doug runs out of this wire i will regret it later. Most of the cloth wire online is really chessy stuff. Thanks for the compliment. I cant wait to hear it.
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Found some 47pf Erie 1kv Ceramic caps for the PI plate resistors.
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Got the Molded Mica El Menco axial 250pf / 500 volt treble cap today. I bought a bunch of them. They are a little smaller than the originals but good enough for me. Waiting on the 5F6A Chassis to arrive.
Edit: Look where i soldered the treble peak cap on the board! Ha!!!!!!!!!!!
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Treble cap position corrected. That's a first!
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The 5F6A Chassis arrived this morning. I have the board screwed down to the chassis and the transformers in place. I wasn't sure the 1968 Bassman OT would have the same bolt hole spacing but it's dead on. Have to put it to the side for a day but will show the progress of it as it gets built. I used fender short stubby 60's screws to screw the board in place.
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Liking your build
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Liking your build
One part at a time. If i had the time i would be finished in about 3-4 hours. But i have other things to take care of.
I got a little more done earlier today. Tonight i'm taking a break/
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What size of self tapping screws do i need to buy from Doug for the (3) Belton preamp tube sockets and (3) 8 pin octal tube sockets?
I want this build to have the best hardware i can find. The hole size in my chassis is 6/32. Will Doug's 6/32 size self tapping screws be a tad wider as they are screwed into the chassis? That's what i need.
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What size of self tapping screws do i need to buy from Doug for the (3) Belton preamp tube sockets and (3) 8 pin octal tube sockets?
I want this build to have the best hardware i can find.
what is the ID of the hole?
--pete
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All tube sockets holes are drilled 6/32
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I would use 4-40 x 1/4" with kep nuts for all tube sockets on that chassis. I tap my own 4-40 threads when I'm working with a blank chassis.
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Well, looky that. A 60's Bassman output tranny will fit. Never thought of that. I have one of those and 2 Bassman chassis I got in a trade.
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I would use 4-40 x 1/4" with kep nuts for all tube sockets on that chassis. I tap my own 4-40 threads when I'm working with a blank chassis.
I was hoping to not have to use nuts on screws. So is the 6/32 self taping screw 6/32 at the base of the phillips head?
Also i am thinking a 6/32 head will butt up to close into the preamp socket base.
eleventeen (http://el34world.com/Forum/index.php?action=profile;u=2988) i was really surprised that the holes for the OT were spot on and not a hair off.
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Plus i think a 6/32 head will butt up to close into the preamp socket base.
That's why I use 4-40 on sockets. 6-32 will not fit my Cinch noval sockets.
Since your chassis holes are already drilled your options are kinda limited. Unless--- you rotate the sockets and drill and tap new 4-40 holes. Not something I would do on a chromed steel chassis.
Kep nuts ain't gonna be seen in that crowded tweed chassis. :wink:
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I predict: you're not going to be happy using 6-32 screws on most 9 pin sockets. You put that all together and it just doesn't sit right; the screws don't sit quite vertical through the chassis...one screw eats up all the tolerance for the other one. The heads are a bit too big, too, unless you get a specific variation of pan-head with a slightly smaller head diameter. Most Chinese 9-pin tube sockets don't have mounting hole clearance for 6-32....I don't know what mfr you are using. Some older US made phenolic or black sockets can pass 6-32 without enlarging the mounting holes. I reco you go for 4-40, I think you'll end up a lot happier with the finished product and it will go together with much less grief.
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I want this build to have the best hardware i can find.
I would use 4-40 x 1/4" with kep nuts for all tube sockets on that chassis.
Sluckey's suggestion is the finest hardware in this case. Only step up would be the same but stainless steel.
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run with 4-40 for the 9 pin and 6-32 for the octal. you can use 4-40 for the octal, but 6-32 hardware fits better. use 1/4" with a keps nut. i use stainless for just about all my builds.
loose fit or close fit 6-32 hole? why asked what the actual hole diameter is. if the hole was drilled for loose or close fit BOLT, then to install a self-threading screw, you'd need to use self tapping screw that fits and cuts thread. assume the hole was drilled @ .149" for 6/32 bolt, then you'd need to use a #10 self tapping screw to cut thread with type A, AB, B, or 25 self tapping screw - see chart below.
http://www.shender4.com/thread_chart.htm (http://www.shender4.com/thread_chart.htm) <---- for machine screws
http://www.ebninc.com/technical/screws-self-tap.pdf <---- for self tapping screws
--pete
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This guy has a large selection of stainless hardware, at cheap prices:
http://stores.ebay.com/Albany-County-Fasteners?_rdc=1 (http://stores.ebay.com/Albany-County-Fasteners?_rdc=1)
Jack
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Great replies. I will go with the 4-40 (was thinking MOPAR) for a minute here. 4-40 for the preamp & 6/32 for the octals.
More later. Much thank all!
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Good decision. What you said earlier----that 6-32 screw heads are a bit too big and will impinge on the area they go in when mounting 9-pin sockets---it is very true. I don't know what the particular head type Fender used on their screws is called. It is smaller diameter than nominal pan head but larger than filister head. "Modified pan head?"
I can tell you, you'll completely hate life if you try to use 6-32 on a chassis where you cut/drill the holes. The big hole and the two small holes have to be made with better than NASA-grade precision or they will simply not sit properly, and even then....... The heads interfere with the tube sockets, the screws pull against each other, it's a mess. And to gain what? A 4-40 screw is only 20 times stronger than it needs to be to secure the tube and socket under any imaginable conditions versus 50 times stronger as a 6-32 would be? Save yourself the grief.
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I ordered 12 of each. 4-40 with kep nut and 6/32 with kep nut. Also 2 Carling switches. I am using Marshall tube sockets instead of the fender type. Those Marshall sockets really grab power tube pins good. I just don't like the new fender sockets. Retention a few time and the pins break off. Maybe there is a good Fender socket someone could recommend before i commit to using what i have?
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I am using Marshall tube sockets instead of the fender type. Those Marshall sockets really grab power tube pins good.
Which 1's?
Got a picture/description/company model #?
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I am using Marshall tube sockets instead of the fender type. Those Marshall sockets really grab power tube pins good.
Which 1's?
Got a picture/description/company model #?
The Belton socket pictured.
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Oh, Ok, thank's. :icon_biggrin:
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Today progress. I'm tired/ :help:
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More/
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I went to the ACE hardware store and found the 4-40 preamp socket screws & 6/32 octal socket screws. I just had to get those sockets mounted so i could get some work out of the way. The 4-40 screws with nut are perfect! Everything went pretty smooth.The worst part is yet to come. I actually dread heater filament wiring. It's not as bad as it used to be for me to do but i still hate the getting the wiring exact looking on all sockets. I simply (Hate) heater filament wiring. Give me a chassis run over by a truck and i am happier. :laugh:
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Looking great!
Oooo, next the dreaded heaters. :BangHead: :cussing: :laugh:
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I always lay in heaters first on a tweed chassis; last on a blackface chassis.
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I don't have any green heater wire. I feel better now. I will order some from Doug now.
I decided to put a switchcraft jack between the (4) RCA speaker out connectors.
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Power transformer from a 1962 Wurlitzer Organ. 360-0-360. Not sure i will keep it in the amp. I was shooting for 325-0-325 for the original Tweed Bassman B+ of 400 VDC on the power tube plates. Will see/
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Nice work Plexi.
I have a chassis similar to yours, just a bit smaller. I gutted it for parts and was going to chuck it as the layout was not great.
I held onto it just in case. Not looking forward to squeezing a board into it. :think1:
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Power transformer from a 1962 Wurlitzer Organ. 360-0-360. ... I was shooting for 325-0-325 for the original Tweed Bassman B+ of 400 VDC on the power tube plates. ...
I believe you'll have over 450vdc loaded, and a tad over 500vdc unloaded.
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Power transformer from a 1962 Wurlitzer Organ. 360-0-360. ... I was shooting for 325-0-325 for the original Tweed Bassman B+ of 400 VDC on the power tube plates. ...
I believe you'll have over 450vdc loaded, and a tad over 500vdc unloaded.
Yeah i know it's not the right PT for this.
I am just going to spring out in the morning,load my visa and buy the right PT for it. I have come this far and i don't want to skimp and wind up with a Tweed Ampeg. The PT has been removed/
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I got the advertised 325-0-325 PT this morning. Unloaded i decided to check the HV A/C recto leads and i am getting, Edit 340-0-340. Will see what it winds up being after it is under load. I should be seeing 325-0-325 on my DVM. I am almost ready to flip the switch and hear good stuff. But i ran a foot short on the heater wire i had got from Doug. Ordered more and it will be here friday. All in all the hard work is finished minus 12" of heater wire from the PI pins 4&5 to the octals and lamp.
NOS Sylvania preamp 12AX7A tubes. NOS 1958 5U4GB for now. Bogen 6L6GC power tubes for now.
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I also need to take a 1968 Fender doghouse to a machine shop and get it shortened up by a few inches. Width and screw hole spacing is spot on. Length is over sized a bit.
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Oh i almost forgot the NOS 12AY7 V1 tube. Have 12ax7's in my mind and over looked that.
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Finished heater wiring and fired it up. Sounds pretty darn good. Checked bias and plate voltage. Stone quiet amp at idle.
Plate voltage after 30 minutes is steady at 419VDC. Bias in grid volts is -53 VDC. Schematic says -48. I am using a 5U4GB rectifier seeing as i used the last GZ34 i had earlier this week on another amp. The V1 cathode voltage is as the schematic at 2.500 volts. I will post the voltages later on the valve voltage page after i get another GZ34 and do some comparisons in tone and voltages. I am very satisfied as to the entire build process. It went smoother than i expected. I'm sort of burned out building amps. After i built the board i was basically committed to find the chassis and go for it.
More later/ :worthy1: :worthy1: :worthy1: :worthy1: :worthy1: :worthy1:
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Final/
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Great job all around!!
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Thanks HBP! I have been wanting to do this particular build for years but always got side tracked.
Remember that 1955 Bassman i found for pennies? That got me started on my Tweed kick.
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Really looks good! That would make a nice plexi conversion! :icon_biggrin:
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Really looks good! That would make a nice plexi conversion! :icon_biggrin:
If i had my way i would get bed sheets and T shirts with the 5F6A print on them. No socks though. :laugh:
Bigger Pic's / http://triodeamplification.com/5F6A.HTML (http://triodeamplification.com/5F6A.HTML)
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Got the 1968 Super Reverb Doghouse pan shortened up back from the metal shop today. Have to do a few little cosmetic finishing touches but it fits perfectly. Have it wired through rubber bushing and mounted. This is as close to the real thing as i am ever going to own. Waiting on those 1959 Tungsol 5881 tubes.
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very nice build. congrats.
--pete
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I think i have some OCD going on here. Selenium rectifier.
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Ha! Wrong color. Why not just bolt it down and hook it up?
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I tried so bad to find the light blue one but no luck. Most of them on Ebay are too big as well. The other orange ones are pretty small (penny size).
I am am not sure what they are rated at either. I have like a 58VAC bias tap. Educate me on these rectifiers.
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Can i use this orange one from the box?
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Ha! Wrong color. Why not just bolt it down and hook it up?
It works! :worthy1:
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I was just kidding. I left the selenium rectifier in my 5F10 just because it was working, but if it ever fails I'll replace it with a trusty 1N4007.
I never bought into the amp forums' chatter about toxic poisons associated with selenium. I've worked with selenium rectifiers all my life, some as big as gallon paint cans. I respect the fact that they are poisonous but I don't intend to eat one or smoke one. I don't chew on lead or sip antifreeze either! :icon_biggrin:
Back in the late '60s we used to occasionally pull a trick on the instructor in tech school. At the end of the day the circuit breakers for lights and work benches would be turned off. Someone would connect a SR across a tv cheater cord and plug it into a workbench outlet. Whoever turned the breakers on the next day got a strong rotten egg smell as the selenium rectifier smoked! We didn't know it was poison gas back then. No one ever suffered except for the foul smell. Well, there was that one time with Billy, be that was probably the mushrooms! :laugh:
Anyhow, at least you know how to connect one properly. And if you ever smell rotten eggs, you'll know where to look. :icon_biggrin:
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That a real good story! Man i don't want to smell that smell. I used to drill water well's in the early 1980's. The sulfur smell of rotten eggs is pretty bad at times. Depended on how much vegetation and such from the Dinosaur era there was.
I drilled Lion Country Safari's well in Palm Beach at 800'. I had someone with a shotgun keeping an eye out for lions while drilling in the field. Looking back i don't think i would do that again.
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I couldn't resist buying these NOS 1958 CBS 5881 tubes. I feel like i am paying alimony to my 5F6A amp.
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CBS made tubes, so I assume they made those. But aside from the label, those look 100% like 50's Tung Sol 5881's.
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Yes they sure do HBP. And maybe a tad more robust. But what turns me on is the script on the box:
A Division Of Columbia Broadcasting System Inc. Guaranteed 1000 year usage! Ha!
Edit: I ran across a tube store that has these same tubes and are advertised as being made by Tungsol.
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I am going to try a NOS RCA GZ34 i just bought and compare voltages with the NOS CBS 5U4GB i have in the amp now.
I looked at cheaper tubes but i just have this thing for vintage real tubes made of stronger metal than they use today.
Welded plates vs Stapled plates as well.
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Oh you have an RCA GZ34, nice! :icon_biggrin:
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Oh you have an RCA GZ34, nice! :icon_biggrin:
Not yet. Just paid for it. Looks nice
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They want money for those.
I have been able to get NOS RCA 5V4A tubes for under $10 each. No, it ain't a GZ34. It ain't $50 either for a dumb rectifier. But it's a robust tube w/indirect heating and the later ones, the ones that are NOT shaped like bowling pins but same envelope as RCA 6L6GC: straightsided but with that slightly rounded top. Those are nice tubes.
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Power transformer from a 1962 Wurlitzer Organ. 360-0-360. ... I was shooting for 325-0-325 for the original Tweed Bassman B+ of 400 VDC on the power tube plates. ...
I believe you'll have over 450vdc loaded, and a tad over 500vdc unloaded.
Yeah i know it's not the right PT for this.
I am just going to spring out in the morning,load my visa and buy the right PT for it. I have come this far and i don't want to skimp and wind up with a Tweed Ampeg. The PT has been removed/
it'll sound better with the higher b÷.
--pete
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The 5V4 is a fine tube. I used to have some of them. I am looking forward to hearing the amp with that GZ34.
I look at it and don't believe sometimes i actually built it with all the old parts i could find. And that they were all good parts.
I wanted to do it proud
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Amazing build, congrads
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Amazing build, congrads
Thanks much mscaggs. Cant wait to get the tweed head cab being made by John Mergili
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I am going to try a NOS RCA GZ34 i just bought ...
RCA box & label, but that's a Mullard GZ34; again 100%.
The plate structure, "Made in Great Britain" label, hole in the guide post and 2-line code in faint gray on the glass (above the "RCA Electron Tube" on the base) confirm it's a Mullard GZ34. Hard to see, but the 1st character in the upper line of that code looks like a "B" which indicates Mulard's Blackburn plant.
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Bravo !! :bravo1:
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I am going to try a NOS RCA GZ34 i just bought ...
RCA box & label, but that's a Mullard GZ34; again 100%.
The plate structure, "Made in Great Britain" label, hole in the guide post and 2-line code in faint gray on the glass (above the "RCA Electron Tube" on the base) confirm it's a Mullard GZ34. Hard to see, but the 1st character in the upper line of that code looks like a "B" which indicates Mulard's Blackburn plant.
I have had a lot on my plate lately (not tube related) and didn't even notice the hole in the guide pin and BK Mullard script before i purchsed it. I stole that tube for $125.00 + $5.95 ship. Thanks for noticing all that HBP.
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... didn't even notice the ... BK Mullard script ...
The "BK" on the tube base is RCA's date code. Look on the glass above the "A" in "RCA" for a faint code, 2-lines made of ~3 characters per line. The 1st character in the top line is probably a "B".
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What is the big deal with the GZ34 Mullard? The metal base ones bring insane money. I have a a few around. One has Heath on it another Amperex and a couple of RCA's as well. I have heard they are very durable, but is there some other reason they are in great demand?
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What is the big deal with the GZ34 Mullard? The metal base ones bring insane money. I have a a few around. One has Heath on it another Amperex and a couple of RCA's as well. I have heard they are very durable, but is there some other reason they are in great demand?
I wonder why they are so expensive as well. No answers from me. I can now see the faint digits HBP
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What is the big deal with the GZ34 Mullard? The metal base ones bring insane money.
I wonder why they are so expensive as well. No answers from me. I can now see the faint digits HBP
1 reason is the Hi-Fi guy's love them.
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What is the big deal with the GZ34 Mullard? ... I have a a few around. One has Heath on it another Amperex and a couple of RCA's as well. ...
A number of sources talked them up as the ultimate GZ34 (Mullard, as well as Amperex/Philips in general).
I have a few as well, never used them in anything. To me, a rectifier with a larger voltage drop makes more sense in a tube amp where you want rectifier-sag or rectifier-sound...
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I wonder what the date code will be. I will have it here Wednesday.
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I am wonder what the date code will be. I will have it here Wednesday.
From a probably-reliable source (http://pax-comm.com/rcadates.pdf), Feb 1967. The Philips factory codes I pointed you towards on the glass carry their own date code, and could be used to corroborate the RCA-brand date code.
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I am wonder what the date code will be. I will have it here Wednesday.
From a probably-reliable source (http://pax-comm.com/rcadates.pdf), Feb 1967. The Philips factory codes I pointed you towards on the glass carry their own date code, and could be used to corroborate the RCA-brand date code.
Yes i found that source info as well earlier tonight and saw RCA's secret code. BK Philips to reflect Feb 1967.
I think i can see The letter F ? B 2 but it is clearly eye ball guessing from the faded angle of the picture.
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Wow this is an amazing work ! :bravo1:
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Wow this is an amazing work ! :bravo1:
Thankyou uki.
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Received 5AR4 / GZ34 this morning. Pin#4 dead. No filament or emissions. Bummed out. D*m! :cussing:
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Refund for DOA? (I hope)
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Received 5AR4 / GZ34 this morning. Pin#4 dead. No filament or emissions. Bummed out. D*m! :cussing:
if you want it, i have a used GE 5AR4 with plenty of life left. 35bux + postage. last used one i have.
--pete
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Refund for DOA? (I hope)
The seller says they have more NOS 5AR4 tubes and will do an exchange. I sent the bad one back yesterday.
Thanks DummyLoad i may take you up on that offer.
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Got a refund on the DOA RCA GZ34. Decided to grab this Amperex Bugle BOY GZ34 while i could.
Steve i found the powder blue Selenium rectifier. 1961 Date. :icon_biggrin:
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Steve i found the powder blue Selenium rectifier. 1961 Date.
Great! I heard that most of the Bassman magic is inside that rectifier. Don't let the stink out!
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Steve i found the powder blue Selenium rectifier. 1961 Date.
Great! I heard that most of the Bassman magic is inside that rectifier. Don't let the stink out!
Ha!!! What if i put a moth ball next to it? :l2:
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Ha!!! What if i were to put a moth ball next to it?
Moth balls are easier to chew than selenium rectifiers. I loved that smell when I was a kid! :icon_biggrin:
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Ha!!! What if i were to put a moth ball next to it?
Moth balls are easier to chew than selenium rectifiers. I loved that smell when I was a kid! :icon_biggrin:
Moth balls did have a strange smell . If you sniffed to hard it would make your eyes water. Never sorted a moth ball.
Maybe that's the next craze we will here about in the news.
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I received the Amperex GZ34 this morning. The code from what i can see is,
1 07
f33
LOD
My B+ is now 425VDC (edit: (430 VDC) and bias grid is -48.5VDC. The amp does sound good with the plate voltage up from 408 VDC.
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:icon_biggrin:
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I received the Amperex GZ34 this morning. The code from what i can see is
...
f33
LOD
That "L" is almost certainly a right-triangle. The right-triangle indicates Amperex's Heerlen, Holland factory.
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I received the Amperex GZ34 this morning. The code from what i can see is
...
f33
LOD
That "L" is almost certainly a right-triangle. The right-triangle indicates Amperex's Heerlen, Holland factory.
I am using magnifier lens and still cant see it all that good. This is the best pic i can get of it. Very difficult.
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Received the Tweed Head cabinet this afternoon. Just beautiful Craftsman ship. I had no trouble getting the holes marked and drilled for the screws. Of all things, i forgot i don't have any power cord retainers.
The Peavey 410 cab doesn't look so nice in comparison.
John Mergili sure does nice cabinet work. :worthy1:
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Wood knots!
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Dam this amp sounds incredible! Not to brag but man this thing is different than just another amp build for me. I have had several people play it and it is exceptional. I suppose that 4 ohm OT has it under control.
2 Ohm is loud but tone suffers. 4 Ohm has less bass and mid's but tone is greatly improved from what i have read online with a 4 ohm OT.
Of course this was a Hi-Fi thread i got this info from. Got the 5F6A Bassman tube chart and early 60's power cord retainer for it.
I'm in awe of having actually built it with all the NOS parts i have been able to find.
I will do a sound clip of it soon. More than a keeper.
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excellent workmanship. :icon_biggrin:
--pete
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I found a 1959 8087 power tranformer in a 1960 6G6 Blonde Bassman i worked on 2 week ago. I was drooling. Real early 6G6.
Never expected to see one in anything other than a Tweed Bassman. Pic of it/
Look at the circle on the transformer with the (T) inside of the triangle. It measured 380-0-380 VAC/