PC Engine Duo - recap, CD-ROM calibration and audio fix

This PC Engine Duo arrived in a state “occasionally loads CD-ROM games but has major audio issues”.

Diagnosis

Given the experience on PCE Duo, an unserviced PCE Duo certainly needs a recap first. The audio issue may very likely related to the leaky capacitor. Only a matter of to what degree.

Open up and found leaked capacitor.

You may think it's dust but they are dried electrolytics

And Hudson bee too :)

The repair

First to remove all the 55 capacitors, and clean up the board.

Fit all the new capacitors in.

The next step is CD-ROM calibration.

Test shows ADPCM sound is missing. This is mostly the voice acting in games. The leaked electrolytics has damaged several VIAs and traces in audio circuitry.

Headphone dial wheel isn’t working, not a big deal but worth fixing.

Finally the audio will disappear after warming up 10-20 minutes. Checked on oscilloscope, the wave from the amp IC506 is getting flatter when the console is on for a while. Replace the amp, but still having issues. Found there is a reference voltage ground has a marginal continuity due to corrosion from the leaked capacitor, again. Fix them.

Some of the trace repairs on the top:

Some of the trace repair on the bottom:

The result: a fully working PC Engine Duo.