Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Drgitpiker on April 07, 2020, 04:16:14 pm
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Hi, ive got a strange problem? I have a diy princeton aa1164 build that has hammond m3 organ transformers. Power xformer voltage was to high with a 5u4, but fine with a5y3. The amp had ghost tones mainly on lower strings. I switched output xformer leads to the plates and the ghost tones went away , but now I have no tremolo. Anyone had a problem like this? :dontknow:
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using this schematic;
https://el34world.com/charts/Schematics/files/Fender/Fender_princeton_reverb_aa1164.pdf
I have a diy Princeton aa1164 build
gonna say based on your description above, a wire got knocked loose, a iffy solder joint failed, foot switch didn't engage,............
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No ,it not that I should say there is a very small amount of trem but almost inaudable. Havent tried switching it back yet to see If the trem returns. Thank for responding .
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I should say there is a very small amount of trem
That very small is also a MAJOR part of your bias circuit.
I would highly recommend checking the bias since they are both interconnected by wire :icon_biggrin:
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I switched it back , the ghost overtones came back and so did the trem. I tried switching the coupling caps around, ghost tones went away, so did the trem I have adj.bias, tried high and low bias settings, still almost no trem. When I first got the amp up and running, the trem for me was a little weak. I changed the 1m trem coupling resistor to 500k , got it to my likeing, if I spead up the trem to 8 or higher on the speed the trem would fade out intill I slowed it back down, then it would slowly fade back in. Tried a different tube in v4 ,no change. It seems to be a phase problem.
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I guess no one has any idea what wrong with my amp. If I switch xformer leads around on th 6v6's, I have tremolo ,but with nasty overtones and harmonics. Switch it back good amp tone , very weak trem. HELP !
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Forgot to mention, I put the Paul C pi mod from the start, so I never ran the amp with the stock pi wiring. Could the modded pi cause this problem? :BangHead:
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To start diagnosing the problem, we need to see the voltages throughout the amp. (Including the DC voltages for B+ and each HT node, and all the plates and cathodes.) While you’re at it, check the AC voltage on the sockets heater pins.
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Well guys it took me a few days, but I found the problem. The cathode resistor on v4a the trem side is a 3.3k. By mistake I grabbed a 33k. At 66 my eyes aint what they use to be. Now I have more trem that I know what to do with. Had another problem that was in the reverb. With the hammond organ xformers my b+ was on the high side, changed to a 5y3 and that helped was getting a buzzing distortion when id hit the strings a little harder. It would get louder when I turned up the reverb. Turned out to be to much voltage on the reverb xformer. Moved from the b to c node , no more buzz. Got this amp all biased in. It sounds killer. With all that overkill Hammond iron, it has headroom for days , no sag in this power supply,its on a double dose of viagra ! LOL Thanks for the responces.