Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: rutledj on August 31, 2021, 06:43:08 pm
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I built the princeton reverb found on this site. It sounds great, everything works as expected, but when I play certain notes (like the G on the low E string, 3rd fret), I get all kinds of static noise through the speaker. I've taken the chassis out of the cabinet and hooked it to an unmounted speaker to try to eliminate the cabinet and it still does it. I tap on the chassis (anywhere on it) and I get the static. I've tried new tubes, resoldered all wires and components. Not really sure what else to try. Voltages all look good.
Any suggestions?
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Double check all of your grounds.
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bad connection somewhere
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I would "chop Stick" every connection see if you can make it make the noise.
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> certain notes
Can you hold those notes? Friend? Signal generator?
Then take a rubber-ended pencil and try holding it various places to damp the mechanical vibration.
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Good idea with the signal generator. I'll try that. Have one I built over 35 years ago in tech school!
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Well, spent the last week completely taking the amp apart, replaced every wire, put in brand new tube sockets, re-soldered every connection, tightened down every pot and jack, put in new tubes and tried a different speaker.. Dang thing still has that static noise on certain notes. Tapping almost anywhere on the chassis, board, or any tube will also create the static. Completely disillusioned at this point. Have no idea what to try next.
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Hello, have you tried a different instrument cord and guitar? Also you prolly need to try different tubes. Does it do this with the reverb driver V2 pulled ?
Oops reread and see you tried different tubes.
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You have already tried a ton of ideas. Persistence is the only answer I can offer. Once I had a volume pot that got solder or flux inside and showed that symptom. I was chopsticking it for the 11th time when I finally noticed that pushing on one of the pot terminals made a little static. New pot was the permanent solution. Good luck with your brain-teaser.
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I think I'd find a spot of the fretboard where it consistently makes the static sound and adjust every pot one at a time and see if it goes away. Static as you describe it has also in my experience been a cracked or insufficient solder joint of a ground termination and would make the noise when there was physical vibration or shock, like you describe. It could also do it with sympathetic vibration from a certain frequency being played on the guitar. Some pictures of the inside of your amp could be helpful.