[SOLVED] PCE Duo - Recapped - 6270 replaced - all great except... NO CD Audio

[bitwiz]

Hi all, My first time posting here.

I have a PCE Duo. I bought it already recapped. It was fairly good work, with the board cleaned. It had only 1 trail jumped to fix a small corrosion.

It all worked (including CD Audio), but it had a random graphic glitch, which the previous owner did not get to the bottom of.

It took me a while to figure out that the problem was the 6270?probably a busted memory cell.

I got one from a white PCE donor and swapped it. It fixed the issue, and I was happy!

I assembled it and stored it away a couple of months ago.

Two days back, I decided to play a CD game on that bad boy. I fired it up, and for my surprise there was no CD Audio.

I tried to play a music CD, but there was no audio. Game FX works with no problem.

I have been trying to find the issue with no luck thus far :-(

Any ideas?

I suspect it could be the DAC LC881M, but how can I test it properly?

Is it possible that by changing the 6270 I busted something else that messed up the CD Audio?

Granted, I transplanted the chip and had to reflow/touch up the leads to get it to work (it was not a hole-in-one), but come on!

Any pointers or ideas on how to diagnose this would be deeply appreciated.
 

[Keith Courage]

There are many traces and via hole connections that can go bad from old capacitor leakage. I doubt the LC881 is bad.

Check all the traces and via holes above the 7805 heatsinks.

Is all audio missing? If so, the 4558 op amp near the AV port should have 3.8V or around that going to two pins on the op amp. If that voltage is missing, find the bad connection. IF there is too high of voltage there, Ground to the op amp could be bad.

There could also be a bunch of old leakage under the 4558 op amp itself which would require you to remove the amp, clean under it, re-install and then repair any connections that could still be bad after wards.

Also check for leakage under 4558 op amp under the board that is near the oki5205 chip.

[bitwiz]

Thanks a lot, Keith Courage! Regular audio is all good. Only CD audio is missing. Given that, any of the 4558 amp area in particular would be more suspect and I should tackle first?

[Keith Courage]

If only CD audio is missing, there is a 4558 op-amp that controls this. It's on the bottom of the board but usually this amplifier isn't bad. Most likely you have some bad via hole connections.  I can post a picture of it later tonight but I'll try to describe the area as best as possible now.

Look above the heat sinks for the voltage regulators. There's a section just to the right where there's a 22 and 47 microfarad capacitor right next to one another. The via holes for both of those capacitors lots of times need new connections run through them. Also, it's not uncommon for the via holes just to the right of those two capacitors to need new connections run through them as well. So basically check all the via connections around those two capacitors.

[bitwiz]

Hi Keith, Indeed. I found a few corroded via-hole connections in the area (7, to be precise).

I patched them, and CD Audio is back. All working now.

Thank you so much!

Best,