PC Engine Duo Sound issues

Hello,

I recapped a PC Engine Duo a few weeks ago, and immediately ran into crackling sound issues. It's mostly sat on the shelf because I've been busy with the end of my college semester.

I have since re-cleaned the board, and now instead of the crackling sound issues, I get what seems like no sound. However, if I crank my PVM to max volume I can faintly hear the sound, and it sounds like it should. If I'm not mistaken this is a sign that the amplification circuitry is malfunctioning.

My guess is that I have a dead trace or via somewhere, and I'm having a bit of trouble tracking it down.

Does anyone have any suggestions for this? I know the op amp circuit near the AV jack has some issues, as the voltages seemed off when I probed around. (1.4V on the output, 3.8ish on the non-inverting, and I think 4 on the inverting? Been a bit since I measured it.)

Has anyone reverse engineered the audio circuitry in the PCE/Turbo Duo? Some sort of a schematic would be extremely helpful here.

Thanks in advance for any help. It's appreciated.

 

bump

 

I managed to figure it out, and repaired both the hucard and CD audio for the console.

The problems were a missing ground connection on an op-amp, and a missing 5V rail to pin8 of the M51131L volume control IC. 2 jumper wires and the audio was working perfectly again.

After that I went to reset the laser, and found that it was a bit... touchy. It likes to randomly go out of calibration, so I decided to just replace the entire HOP-M3 laser assembly and tune the new laser.

May also need to replace some of the trimmer pots for it if that doesn't fix the issues.