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Apt Amplifier Model 1 amplifier question - buzzing

Gazdatronik said:
They were trying to do a lot in not enough space. I agree, the chassis should have been 1 rack unit taller.
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I have been listening to this amp for the whole evening yesterday. It sounds so good. I was poking around the wiring with a wooden stick between listening periods. I can get buzz slightly quieter, but wires are very stiff and there is no space to move them around, so I'm afraid of breaking the solder joints where they are attached to the boards.
 
ViperZ said:
I have been listening to this amp for the whole evening yesterday. It sounds so good. I was poking around the wiring with a wooden stick between listening periods. I can get buzz slightly quieter, but wires are very stiff and there is no space to move them around, so I'm afraid of breaking the solder joints where they are attached to the boards.
Click to expand...
A possibility, but not a probability. Sounds like you are on the right track though.
 
FWIW I have one too and it has never buzzed with or without input connected. My unit was purchased in 1981 (ser#03543) and according to the service manual it has the Rev 3-6 amp and display boards, so maybe OP has an earlier unit. Holman built these amps to last. Despite continuous use my unit has never skipped a beat and has all original parts which is amazing given its vintage. I recently checked bias (first time ever) and it was right on in both channels.
 
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