Sound problems after recapping my Turbo Duo

[mario_pic]

its likely an open via by the heatsinks and the 10UF caps

I made a headphone probe  unit to test the sound so far I got clean good sound from the c6280 chip on both left and right audio out points wondering if anyone knows where the first vias for sound feed what amp ic on what leg  so far pin 18 and 19 are left and right audio on the c6280 ic

[thesteve]

if its chip sound the first stop is the last stop
amp chip between the heatsinks and AV port

[Valkyrie]

I just recently finally started digging into this thing again.  I removed all of the amp caps and started testing a bunch of traces and vias,  but I didn't find anything else obviously bad.  I put it back together and was going to try BlueBMW's suggestion of following the schematic and probing for audio.  But after plugging it up with a new AV cable, I actually found that it worked pretty well! Turned out, the left audio channel on my other cable is flakey.  So that was part of my problem.

In testing it for a while, it seemed good until I realized that the sounds from the ADPCM channel were very quiet.  Looking at the multiplexer schematic, I saw it was handled by IC503.  That's the one I removed to repair a couple vias when I did the cap job.

I took some voltage readings, and confirmed that it had ground on 8v on pin 8.  But where the schematic says it should have 2.5v on pins 3 and 5, I'm getting about 3.8v.  And in checking the other pins, they're all reading 3.8v also.

So I'm not really sure where to go from here.  Does this sound like a bad opamp at IC305?  And is the high voltage on pins 3 and 5 a problem?

[MNKyDeth]

Diagnosing the sound issues on the TurboDuo/PCE Duo has been the hardest for me. After a lot, of console repairs I have found that you need to measure the voltage on the top and bottom of the board around the op-amps.

Specifically, IC506, IC503 and IC521. The areas where the traces go through the PCB to the other side of the board I find get plugged up with gunk. Sometimes they are just bad and you need to run a wire from one side of the board to the other. Follow each ground trace to ensure each ground is really ground and not getting voltage somewhere because of corrosion and electrolytic fluid issues.

IC502 is almost always good although I have run into bad IC505's because of so much corrosion on the legs, they just had to be replaced cause the legs on those chips were literally trashed.

If voltages are not within range on the op-amps there is either a short or bad trace and this I typically find by starting with following ground on pin 4 of the op-amps.