As many of you already know, I had recently gotten a PCE Duo that the CD sound and the ADPCM sound was not working. Over the weekend I did a ton of capacitor replacement work on the board.
Day 1: When trying to open the unit to take stock about what capacitors I would need to get, after I unscrewed the main cover, a capacitor literally rolled out of the case when I turned the unit upright to remove the top cover. I knew I was in trouble then! But I was also taking this as a good sign that replacing capacitors would be a good thing at this point... Never seen that before - a capacitor rolling out of a unit...
I took stock of the capacitors that I would need, and went to the local Radio Shack. I had to settle for a mixed bag for the type of capacitors - radial, non, polarized and non.
I took it slow and replaced the capacitors one by one in the area marked in many previous pictures as the audio amplifier area - and the capacitor that fell off - a 47uf cap near the front of the unit. I would literally replace one capacitor, then screw things back together and test to see if anything happened - good or bad. Unfortunately, I only had one 22uf cap and really needed more of those. I just took the time to replace some other caps in the nearby region of the audio amplifier area. I found that almost every cap I replaced had either gunky or power residue on the circuit board underneath everything. Another thing I found out - most of the 47uf and 22uf caps were counterfeit caps - probably why they failed and also dried out so badly. At the end of the first day, I had replaced all but 4 caps in the direct audio area, and really needed at least one 22uf cap to complete that area's replacements.
Day 2: Back to Radio Shack - this one was much better stocked, and I was able to get a bunch of 22uf caps and also get a few more space saving versions of some of the other caps.
My first job - finishing the replacement of the 4 remaining caps in the audio amp area. It was not until I replaced the very last cap in that area, a 47uf cap just above the 22uf cap that a previous poster changed that gave them their CD audio back, that the CD audio returned for me. That was great!
Now I was even more determined than ever - I wanted the ADPCM sound too! I replaced all of the 22uf and 47uf caps on the board, replaced the caps next to and nearby the Oki chips on the board, and replaced a few of the larger caps by the headphone output area (I left the smaller 4.7uf caps in place - they seemed to be working). In the end, I replaced over 20 caps on the board. But no ADPCM sound...
](https://www.pcenginefans.com/forum/Smileys/default/eusa_wall.gif "Hitting head on wall")
Day 3: I thought this was good enough for the moment. I only had 6 major caps and a dozen or so tiny minor caps to replace to actually finish a complete replacement. I decided to give one final thing a try - to leave it running for several hours and then see what happens.
I left it on overnight, and the next morning gave it a try. Sure enough, Madou Monogatari did not freeze up in the dungeon anymore, and the special sound effects came out!
So in the end - one weekend's worth of cap replacements and testing is a complete success! I have a totally working PCE Duo!
Many thanks to all who came before me and shared their experiences too!
My own guess: I think it was the two 47uf caps near the front of the board that I replaced that did the trick for the ADPCM sound. Replacing one probably made a nearby crystal start to work properly, and the other probably finally provided the right ground needed for the components in that area - and I think the ADPCM requests filter through one or more of the chips in that area.
