REPAIR GUIDE - TurboDuo: Sound Fix

[Necromancer]

Well done!  Another system saved. 

[DarkRider]

I'm also having trouble with a Turbo Duo. I received one from a friend to fix and when I opened it up it was a mess...   So I went through and recapped the entire system turned it on, and no sound. I found a thread back in October with a similar issue and followed the steps in that thread. All the capacitors seems to check out fine on voltage. I ended up narrowing the issue down to ic506 at the top of the board. I used my rework station to remove the chip and it was a mess underneath it. Cleaned the board and reinstalled the chip and I still have no sound. I did find out that if I short pin 5 of the chip to pin 8, the sound kicks on. Do I have a bad 4558? Can I get away with shorting the pins with a wire, or replace the whole chip or could it be a different issue? Thanks.

[Keith Courage]

Probably bad traces to the 4558 op amp and or old cap goop underneath the op amp shorting it out. So it either needs to be removed,cleaned, and then reinstalled or you will need to bridge some wires to repair the bad traces. I typically do both. Meaning remove, clean and reinstall. then repair any bad traces left behind.

just check the voltage on each pin for the 4558 chip and then check the voltage for the trace that pin would run to and you will easily find out which one is not making a connection.

[DarkRider]

I had removed the amp previously and cleaned under it. I went and removed it again and was checking the voltage on the traces. Pins 3, 4, and 5 had no voltage on them. Pins 3 and 5 appear to connect to a via directly under the amp which I traced out to cap 884. I removed that cap and cleaned the entire area incase some fluid was shorting out around there. What's weird to me is I have about 2.5~ volts going across the cap, but when I have to positive lead on the positive side of the cap and neg on neg, I get a negative voltage across the cap. After reinstalling the cap I now have 7 volts going across pins 3, 4, and 5. Cap 323 had almost no voltage previously and is still currently showing almost no voltage.

Here's a couple photos of the board.
http://imgur.com/a/rqyZn

[DarkRider]

I should add that the sound on the system actually was working better without the amp installed. Still not what it was supposed to be but I didn't have to crank my tv to max to hear it.

[Keith Courage]

Double check the grounds for the 10UF capacitors in that area. Sometimes the via short out.

Also, what voltages are the 10UF caps in the area reading? They should all be around 3.8V.

[DarkRider]

I left today and headed down to Too many games in Pennsylvania. When I get back home on Monday, I'll check. Thank you for the help.

[DarkRider]

So I took the amp off again. I appear to be getting 3.6ish volts (which sounds like it's slightly low) through the 10uF capacitors and the grounds seem to be fine. All of the pads for the amp except where 3 and 5 would be connected seem to be getting the correct voltage, also about 3.6. I get continuity for all of the pad also to the closest connect or via. I keep coming back to c884. Pins 3&5 are connected and also connected to a via through to the other side of the board. The trace off of that via runs to a via that connects to c884 and I'm still getting the weird voltage through the capacitor. I have continuity for the entire trace. Just to make sure I'm not doing something stupid, positive lead on positive side of the cap and neg on neg and I'm getting -2.674 volts which seems low and also seems to disappear after going through it. If I keep tracing it out from there it seems to run to a via underneath the hucard connector that I'm unable to access with out removing the whole connector which I could do but...  Am I doing something dumb or missing something. c884 does appear to be installed the correct direction so I'm not sure why I'm getting the neg voltage through it and why the voltage seems to disappear after it. It seems like the pins 3 and 5 are just not getting the voltage they are supposed to be getting and so when I short them to a voltage source the sound kicks on. Thank you again for the help Keith.

[DarkRider]

So I am apparently dumb. With the amp removed the caps seem to be reading the ~3.6 voltage. With the amp installed. Caps 610 & 604 read closer to 6.6~ Caps 613 & 614 I get about ~2.4. I'm getting ~6.6 on pin 1, ~5.1 on 2, almost nothing on pin 3&5, pin 6 is ~5.1 & pin 7 is ~6.6. I did find a bad via and repaired it, but it didn't seem to make a difference. The Amps on the back of the board and the one near the headphone jack are all reading correctly. Could I have a bad amp? It doesn't explain why I don't have voltage on the pads with the amp removed.

[Keith Courage]

This is what usually happens when there are shorts for the traces that are directly under the op amp. Yes it could be bad though. you could always swap two of these amps around to see if the voltage is still the same which would let you know if it's the amp or not.

[8bitplus]

I've recapped and repaired a few DUO's now and I just replace the amps I remove.  No point re-soldering them back on and risk more heat damage from the process. I got 5x of the RC4558D for about £4 on eBay.
I've used them to replace the 2x OpAmp's under the board and main 2 on top by the AV and jack ports.

[Keith Courage]

I had removed the amp previously and cleaned under it. I went and removed it again and was checking the voltage on the traces. Pins 3, 4, and 5 had no voltage on them. Pins 3 and 5 appear to connect to a via directly under the amp which I traced out to cap 884. I removed that cap and cleaned the entire area incase some fluid was shorting out around there. What's weird to me is I have about 2.5~ volts going across the cap, but when I have to positive lead on the positive side of the cap and neg on neg, I get a negative voltage across the cap. After reinstalling the cap I now have 7 volts going across pins 3, 4, and 5. Cap 323 had almost no voltage previously and is still currently showing almost no voltage.

Here's a couple photos of the board.
http://imgur.com/a/rqyZn

I just had to fix this problem on a DUO. There was a shorted via at R324. This area can be seen from underneath the board near the AV jack op amp. I was getting 7V on most of the 4558 op amp pins as well as the 10UF caps. Hope this helps.

[DarkRider]

You were very close. It was a via for a capacitor. When I fixed the bad recap job that the last person did, a couple of the through hole capacitors had pads end up damaged. I thought I fixed them all but I must have missed 1. I repaired it and checked continuity to the resistors you mentioned and that got the sound working. Now I just need to find some new screws to put in the shell and it will be all set. Thank you for all the help! Now time to recap another express lol.

[Enchurito]

So I have a PC Engine Duo first model that came region modded already to play usa hucards with a switch in the back. It has a long switch thing with a bunch of wires to the cart slot and one to the bottom side of the board where one of the chips has a pin cut off and a wire soldered to it. It also seems to have most if not all it's capacitors replaced. I'm posting because it was working pretty well but sometimes if I bumped the av out port the picture would glitch up or the audio would buzz. Now all the sudden I have no audio at all, not in the headphone jack or the av out. The headphone jack has never worked since I got it. The audio never faded out or had any volume issues, just suddenly nothing. I have tried both a cd and hucard, nothing.

[Keith Courage]

Most likely there are some bad traces on the board in the audio section or old cap goop causing a short somewhere. The majority of the time when people do recaps they do not clean or address this when they should. However, this is also something that can sometimes happen no matter how well things are cleaned up prior. It's going to be difficult to fix the problem on your own unless you are good at soldering and using a multi-meter.

Small chance your AV cable or AV jack is the problem since the headphone jack doesn't work either.

I do these repairs as well as others here(thesteve, turbokon, MobiusStripTech, MNKyDeth). Feel free to message me if you would like to ship it off for repair.