Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on June 06, 2018, 09:21:48 pm
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Beautiful virgin example. A mass of weeds! 1966 pot code dates.
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Chassis pic's
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I do not understand this thing you speak of, this... "lead dress" :laugh:
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I would be very interested to see some of the waveforms from the nest of snake style builds, as well as hear the amp at idle. It must buzz like a bee and hum like a busy housewife doing chores. Parasitic oscillations must be everywhere.
btw, If you ever want to see a marvelous piece of engineering, pick up a mid 60's mechanical cash register, if you can lift it. About 1500 parts including the "dog legs". I worked on those for a while in the 80's. Very complicated mechanics and inevitably the part that failed was buried at center mass. Would you like to upgrade to an electronic, cause this can't be fixed. A regular mode of failure was known as a: Dead Lock. A Dead Lock was cause by a loose shaft, failed bushing, maybe a gear that skipped a beat or two and, the whole internal mass would bind up in jam that couldn't be unwound with a pipe wrench.
Some of the techs when they saw one get wheeled in as a trade in would attack the beast with hammers or whatever as a final act of revenge and defilement to the monsters that had caused them so much grief in the past. The only redeeming attribute about them from the tech side was: As you may recall, the cashiers used to lift the tray and put the large bills underneath. As they did so some bills would drift to the rear of the drawer and end up exiting into the rear of the drawer housing. That was the cause of the other reason to get to the beast when they came in for any reason. Pull the drawers out and look for lost cash. Once an old monstrous 4 drawer unit yielded over $100 bucks.
silverfox.
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I do not understand this thing you speak of, this... "lead dress" :laugh:
I know! There's enough spaghetti to feed 10 people in there!
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I would be very interested to see some of the waveforms from the nest of snake style builds, as well as hear the amp at idle. It must buzz like a bee and hum like a busy housewife doing chores. Parasitic oscillations must be everywhere.
btw, If you ever want to see a marvelous piece of engineering, pick up a mid 60's mechanical cash register, if you can lift it. About 1500 parts including the "dog legs". I worked on those for a while in the 80's. Very complicated mechanics and inevitably the part that failed was buried at center mass. Would you like to upgrade to an electronic, cause this can't be fixed. A regular mode of failure was known as a: Dead Lock. A Dead Lock was cause by a loose shaft, failed bushing, maybe a gear that skipped a beat or two and, the whole internal mass would bind up in jam that couldn't be unwound with a pipe wrench.
Some of the techs when they saw one get wheeled in as a trade in would attack the beast with hammers or whatever as a final act of revenge and defilement to the monsters that had caused them so much grief in the past. The only redeeming attribute about them from the tech side was: As you may recall, the cashiers used to lift the tray and put the large bills underneath. As they did so some bills would drift to the rear of the drawer and end up exiting into the rear of the drawer housing. That was the cause of the other reason to get to the beast when they came in for any reason. Pull the drawers out and look for lost cash. Once an old monstrous 4 drawer unit yielded over $100 bucks.
silverfox.
:laugh:
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Where to start?
Miswired channel 2 input jack. Bad treble pot. Have reverb working. Tremelo works if i touch the intensity pot wires, but need to go through oscillator caps and test resistor values and pots. Bias is equal -28-47VDC per pairs of 6L6GC power tubes. Amp has some balls! Nice reverb.
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I have two valco amps that look the same in terms of wiring "nest". an airline '68 62-9052A that is nearly the same as yours and a 67 Airline 62-9049A which is a transistor version. neither is noisy, neither is buzzy or hums. It looks like a basket case that wasn't thought out, but if you study what things are grounded and where, you'll find there was some planning involved and is part of the reason they are as quiet as they are.
These 2 output transformer amps require intelligence when plugging them into cabinets. There are two output jacks, one at each end of the cabinet next to each transformer but they used a stereo plug. So if you plug in with a mono plug you short one OT's secondary. On my airline they are not marked other than "8ohm". I'm sure a lot of these blew up as heads became separated from cabinets and went in and out of pawn shops, and ended up being plugged into a single cabinet with a mono plug.
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Can you post a schematic?
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Can you post a schematic?
Yes. I forgot how to add them to Dougs library. Let me go fishing and see if i can add it.
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I don't see an email link at the bottom of the schematics page to send the Gretsch Fury 6169 PDF schematic to Doug.
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> if you plug in with a mono plug you short one OT's secondary.
A tube amp, cathode biased, may be safely shorted-out.
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I don't see an email link at the bottom of the schematics page to send the Gretsch Fury 6169 PDF schematic to Doug.
Just attach to a message in this thread. I'll get it to him.
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A tube amp, cathode biased, may be safely shorted-out.
wow! I didn't know that. how does that work?
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Here is a schematic diagramm
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how does that work?
my guess, if you have zero ohm speaker, it will reflect an infinite load on the primary, causing current to slow way down :dontknow:
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I don't see an email link at the bottom of the schematics page to send the Gretsch Fury 6169 PDF schematic to Doug.
Just attach to a message in this thread. I'll get it to him.
Ok here is the schematic i have.
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A cathode-biased tube amp idles full-hot. It runs cooler when working hard into a proper load. If shorted, it runs just as hot as at idle. No harm. (If opened, kick-back can puncture OT insulation.)
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Nearly the same circuit as this Airline. Probably the same as a Supro S6699 and a National N6899
http://el34world.com/charts/Schematics/files/Airline_wards/Airline_wards_gvc_9052a.pdf
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Nice amplifier. Just a mess of wire. Luckily no oscillation problems. But you know there is a lot of coupling going on in there just the same to some degree that effects the tone. Today i can get in and out without much problem. But in the beginning of learning amps, Sluckey and others can tell you i was lost period. All part of learning. Very tedious on the brain sometimes.
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I do not understand this thing you speak of, this... "lead dress" :laugh:
I know! There's enough spaghetti to feed 10 people in there!
They used shielded wire like it was going out of style! Makes me wonder if they had a more compact layout that all the shielded wire wouldn't be necessary...