PC Engine Duo Sound Problems on CD games

[shadowman]

I wonder if anyone can assist me in diagnosing a sound problem I have with my PCE Duo console.

Basically I've noticed that for CD based games certain sound effects are so quiet they are almost impossible to hear. For example:

Tenchi wo Kurau: The voices are all missing (even when playing with them turned on)
Chiki Chiki Boys: All sound effects are almost mute (bar the coin pickup sound strangely)
Dracula X: Certain sound effects like the "getting hit", "window shattering" and the little speech the Grim Reaper gives at the start of the game are all missing. Weirdly the fully voiced intro is still perfectly ok.

The music for all these games play perfectly fine. As mentioned above I can hear the sound effects, but they are so quiet they almost always get drowned out by the CD soundtrack.

Hu Card games all seem ok. For example Street Fighter 2 sounds perfect - with all the music, sound effects and voices all perfectly intact so I believe this issue is most likely isolated to CD games only.

Secondly I had the capacitors replaced on my PC Engine just this week as I was aware of this issue for a little while. I was hoping replacing the capacitors would have fixed things but clearly the issue is ongoing.

Any tips/advice on what might be causing this issue? I've tested the console on two TV's and the problem is present on both, and also tried the games on the PC Emulator "Magic Engine" and the sound issues aren't present there so I believe its a console based issue.

[Niku-Sama]

sounds like this:
https://www.youtube.com/watch?v=WgxVbtoXziI

possible pot adjustment issue

[shadowman]

Yeah, that sounds like it might possibly be the issue. I've cleaned the CD laser and that's made no difference, and the rest of my Hu Cards seem ok. I'll have to investigate this further, hopefully it fixes the issue. Thanks :)

[FABombjoy]

If all other CD functions are good - audio discs play, games load quickly, it could possibly be an issue surrounding the M5205. Either defective chip or problem with the audio mixing circuit.

I've had bad ones before where they distort the audio (I posted a sample (http://console5.com/wiki/MSM5205) here). If it's completely dead I'd probe the audio outputs first to make sure it isn't something further downstream.

[shadowman]

If all other CD functions are good - audio discs play, games load quickly, it could possibly be an issue surrounding the M5205. Either defective chip or problem with the audio mixing circuit.

I've had bad ones before where they distort the audio (I posted a sample (http://console5.com/wiki/MSM5205) here). If it's completely dead I'd probe the audio outputs first to make sure it isn't something further downstream.

Thannks for the tip. I'm quite a newbie at this, how would I probe the audio outputs? Thanks

[FABombjoy]

To probe audio I use a set of cheapo PC speakers with a modified line-in cord. Really you just need to tie the speaker line-in ground (-) to the console ground and then rig something up so you can probe using the line-in positive (+) connection. For audio problems like this I find this arrangement more useful than an oscilloscope... and cheaper too :)

The M5205 generates the ADPCM audio that is unique to the CD-based systems which is probably why HuCards sound fine. It was used frequently for compressed speech or complex sound FX which seems to jive with your list of affected sounds.