TurboDuo - 1 second of audio then cut to silence (Hu and CD)

Started by ZenicReverie, 07/12/2018, 01:42 AM

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ZenicReverie

Nearly 2 years ago I went through a successful full cap replacement on my TurboDuo: https://www.pcengine-fx.com/forums/index.php?topic=21541.msg473529#msg473529

That was followed by happily playing through about 5 games, 4 CD and 1 Hu, over the next year with only a minor stereo issue that I could bypass by adjusting the A/V cable into a different position. I didn't bother to resolder the DIN as I didn't want to disturb a working system any more than I had to. The system has been sitting on a shelf unpowered since then until today when I plugged it in to play a CD game, and noticed there was no sound (again). I tried a Hu-card game, and noted there is initially full audio for about a second before it cuts out completely (tested 5+ times, confirmed each time).

I'm still quite new to troubleshooting audio issues on a console like this, so I'm looking for ideas on how to determine where the fault lies. I have a multi-meter, but aside from an obvious burnt or leaking cap I'm not sure how to determine if any of them have gone bad. I won't have time to open it up and attempt this until the weekend. Any ideas or guidance is welcomed. Will follow-up on Saturday.

Keith Courage

Sounds like bad traces around the 4558 op amp right next to the AV jack. There should be 3.8V going to these two pins on it. If there is not then there is either a bad trace or old cap goop underneath the op amp that needs to be cleaned out.  I like to remove the op amp, clean, then reinstall.
IMG

Oh, I just had one more thought. Might be a bad trace for the ground on the op amp as well. The grounding pin (if looking at the photo I posted) is on the bottom row farthest to the right.

ZenicReverie

That chip does not look easy to replace. I do see what looks like might be corrosion under the top right pin at least. Using my meter I get 0 V between the two even though I can get it to ping. I'm not sure how to check the grounding pin.

I don't think I would have been brave enough to try replacing that with all the caps off when I first replaced them. I think I'm just done with this system. Thanks for the help.

Keith Courage

No reason to give up on it if it can be repaired. I'd be happy to repair it for you if you don't want to deal with it for a small fee.

NightWolve

Quote from: ZenicReverie on 07/15/2018, 10:11 PMI think I'm just done with this system. Thanks for the help.
Not what we like it to hear! Never surrender!!! ;)

ZenicReverie

Quote from: Keith Courage on 07/15/2018, 11:41 PMNo reason to give up on it if it can be repaired. I'd be happy to repair it for you if you don't want to deal with it for a small fee.
I'm not sure I need the console anymore. I've found an emulator that allows me play the remaining CD games off the original discs, so that's probably what I'll be doing. I was planning on selling the console and games once I finished with them. I'm not sure how much I could get for it in the current state though.

Do you think it's an easy fix? If you're up for it I'll send it off to you.

Quote from: NightWolve on 07/16/2018, 12:52 AM
Quote from: ZenicReverie on 07/15/2018, 10:11 PMI think I'm just done with this system. Thanks for the help.
Not what we like it to hear! Never surrender!!! ;)
I'm fairly sure I don't have the tools to replace an IC, and I'd end up damaging it if I tried.

JoeQuaker

Check c604 and c610. Are they make making a solid connection?

Does the audio work correctly through headphone jack?
Mir ist kalt, so kalt...

ZenicReverie

Yeah, both capacitors are making solid contact. The headphone jack has the same issue, power on the system, about a second of full stereo audio, then cut to silence.

Keith Courage

It's the traces to the op amp for sure. Sound for a split second symptom is almost always fixed by repairing 1 or 2 of the traces for the 4558 op amp just to the right of the AV jack.

thesteve

could also be an open connection to one of the center references
check C322 and C323 voltages
should be around 4V

ZenicReverie

As an update. I sent the system off to Keith Courage, and it's now working perfectly. I'm still considering getting rid of the system eventually, but now I can enjoy the games I have left on the actual system instead of emulating. Thanks again!