Xybots sound problem

[nickfredmick]

Hi,

When I play the right side player (Ace) on my Xybots cab the background music is normal but the sound effects are very quiet. The left side player (Rock) volumes are fine.  In the self test mode it seems like the left channel is fine while the right channel is at a lower volume.  The machine has an ‘atari JSA I’ audio PCB.  Sound is amplified stereo through two speakers.
I have read repair logs from other machines with similar issues and tried their solutions without success:  Cleaned the audio PCB, checked wiring and continuity to speakers, checked impedance of speakers, swapped speakers over, swapped out YM2151 and YM3012 chips on the audio board – a random approach because tbh I don’t know what Im doing.
I looked at the schematic for the audio PCB, part of it is shown here:



Do you think the problem might be a faulty amplifier on the board and if so, any idea which chip is the amplifier?
Some of the Integrated Circuits on the board:
6502A (designated CPU in the manual), LM324, TDA2030

Thanks for any suggestions.