Asking for assistance diagnosing a preamp

[coromonadalix]

your orange con19 wire is not good we see the center pin, correct this ...

normally get an service manual, sometimes you can order them directly from the company

1 - check all the psus voltages ac, dc, ac+dc

2 - put the equalizers setups effects to none / off / or flat no correction at all  if there is

3 - i would inject an 0db 1 khz signal and follow it up to the preamp and amp section, always compairing the 2 audio sides( left right) with an isolated main ac voltage scope

4 - try every input line level,  not the phono input if you have one  loll

And yes  you have to do some fault finding logic,  do go here and there thinking this is bad or else,  sometimes you can pull out pcbs  to simplify your search and signal tracing

I had in the past an Sony prologic 5.1 sound system, the bug was after 30min - 1 hrs of use, i had dc component at the output and heard distortion,  tons of boards to check, had to follow the signal path with an scope, an signal tracer, and a signal generator to help, and to my surprise there was a missing thru hole resistor in the amp feedback,  straight brand new form sony  lolll

[adauphin]

your orange con19 wire is not good we see the center pin, correct this.

2-  put the equalizers setups effects to none / off / or flat no correction at all

The CON 19 is probably using the center wire in the Series 2 version, mine only has the single lead.

I do have the preamp in Direct mode...no eq.

I will try all you suggested.