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[Console Repair/Mod Center / Re: REPAIR GUIDE - TurboDuo: Sound Fix]

Hey guys, it's been a while since I last posted here, but I got really frustrated with my Duo repair that I put it aside for over a year and dug it back out today.

Anyways, here's the status:
I replaced all caps, all 4558 amps and even the M51131.

The issue is the following: I get no audio out of the system but I get very very faint sound on the headphones if I crank it up to the max.

Unfortunately I'm no expert, but I read this topic (https://www.pcengine-fx.com/forums/index.php?topic=7328.30) and tried measuring some voltages to see if there's anything suspicious.

So, the 4558 at C506 has a very low output on pins 1 and 7. (Duo_R only had one faulty channel and his amp at 506 had only low voltage at 7).
I also checked the surrounding caps and both the C610 and C604 ones give me lower than expected voltage (again, it's consistent with Duo_R's error, as only the cap at C604 had low voltage for him).

All the other 4558 amps seem to have a correct output and so do the other surrounding caps.

But this is where I'm stuck and I don't know where to investigate further. There might be a bad connection somewhere or damage due to corrosion from the old caps...I'm not sure how to proceed from here. Any suggestions?

[Console Repair/Mod Center / Re: REPAIR GUIDE - TurboDuo: Sound Fix]

2 points
1. adpcm is 1 channel.

I know. Perhaps I didn't phrase my attempt to get it working correctly.
I was just stating, that when I put the ADPCM to one of the AV amp inputs, it came out crystal clear, but when I put the same output from the ADPCM pin10 to the other AV amp input at the same time, the whole sound got messed up.
I'm aware that it's not stereo, but I still have to get the signal on both channels somehow

2. it sounds like you losing it around the AVC.
the avc is voltage controlled, the last one i did wasnt getting the control voltage to it due to a bad via

Anything I can do to test that theory and if necessary fix it?

[Console Repair/Mod Center / Re: REPAIR GUIDE - TurboDuo: Sound Fix]

Yes, I've got a meter. I checked all six 4558 amps and they all get power.

I made some progress, thanks to some very helpful PMs.

I got regular SFX and CD audio working on the headphones, by hooking the output of the upper 4558 (close to the AV port) amp to the L/R channels on the headphone jack. It's just a workaround and not really a fix, but for now it's working.

However, the ADPCM sound is still very faint. I can (barely) hear it, if nothing else plays, but that doesn't really do it for regular gameplay ;)
I put a wire from the M5205's pin10 to one of the 4558 input pins (not permanently, just for testing the ADPCM output) and I got crystal clear sound from it. However, just on one channel, and adding a trace to the other input pin screws the whole sound up.

[Console Repair/Mod Center / Re: REPAIR GUIDE - TurboDuo: Sound Fix]

Hi guys

I recently got my hands on a PCE Duo which was supposed to be working, except for missing sound. I bought it and thought that a simple cap replacement would do the job.
After some online research I stumbled upon this awesome forum and after reading this thread, I was pretty sure that the system could be easily repaired.
When I opened it up, I saw that one of the previous owners already replaced quite a handful of caps around the 4558 amps. I got a little bit worried.


Long story short, I did a full cap replacement (finding a few additional leaky caps in the process), but unfortunately, the problem still persists.

I have full sound from HU card or CD (redbook audio, adpcm etc.), but it's almost inaudible, both on the AV out and the headphone jack.


What could be the cause of this?
I'm considering replacing the 4558 op amps. Could that work? Or does the current problem suggest a different approach/solution?