REPAIR GUIDE - TurboDuo: Sound Fix

[Keith Courage]

I would use a volt meter to find out where voltage is missing. Some traces go bad without any signs of visible damage. Also. make sure the main op amp is getting voltage. Very common for the op amp near the AV jack to have lack of voltage due to board corrosion damage somewhere.

[Zer0-2k11]

Ok i busted out the old multimeter and im getting a rating of 7.81 DC Volts on the Opamp when i place the positive probe onto Pin 8 and the negative probe to ground. I thought the opamp died so i replaced the op amp too as well with the RC4558 but still the same result. Is this normal voltage reading?

[Zer0-2k11]

Double post, please delete.

[Keith Courage]

What voltage are you getting off the positive lead for this cap? Circled in red far left.

[Zer0-2k11]

Im getting 3.88 DCV

[Keith Courage]

Hmm, that sounds correct then. You should have the same reading on the main op amp as well. Sounds to me like the problem is bad traces for one or more of the audio capacitors. I honestly can't suggest which to check next since I didn't do the cap job to know which ones had more leakage or pads lift etc...

[thesteve]

for chiptunes the only amp in play is IC506
check voltages on pin3 (3.88) pin4 (0) pin5 (3.88) pins 1 and 7 (3.88)

[Zer0-2k11]

Ok just got out everything and this is the results,

Multimeter set to DC voltage

Pin 3 = 3.89
Pin 4 = 0
Pin 5 = 3.88
Pin 1 and 7 = 1.45

I think we are getting onto something

The positive pad on C614 did get lifted and i patched it to the closest via with some 30awg kynar wire

[thesteve]

check pins2 and 6
they are your inputs
they feed from C613 and C614, but also get voltage from pins 1 and 7
should be 3.8

[thesteve]

also check voltage at C322
look for black via's by C322 if not 3.88

[Zer0-2k11]

Ok im getting 4.2v on both pins 2 and 6. For C322 im getting 0.030 I don't see any black vias but i am looking

[thesteve]

R321 should be 8v and 3.8
it gets the 8v from a via from the amp power you checked earlier
R321 and R322 are the voltage devider for c322

[Zer0-2k11]

I can see the power rail (Thick trace) that it links too on the IC506 amp . It seems like im not getting any continuity between the via that connects to pin 8 on the IC506 and the positive lead of C322. One of the 2 vias that connect to C322 must corroded damaged. I can't really check the via that connects to C322 as its underneath the 4558 on the bottom side of the motherboard. Would it be safe to link them together with some 26 awg kynar wire?. The via by C322 did look kind of black.

[thesteve]

R322 is the ground side
R321 connects to the power trace

[Zer0-2k11]

Sorry, i did check R321 and im getting the same voltage reading (0.030).

*EDIT* Ohhh i see what your saying. im not getting continuity between the left side of the resistor of R321 and pin 8 on the audio circuit amp.

[thesteve]

looking at R321 one side goes to C322 and R322
the other side goes to a small via, and directly to a large power trace (pin8 all audio amps)

[Zer0-2k11]

Sorry i know what you mean now. im not getting continuity between pin 8 on the amp from the audio circuit and the side of R321 that connects to it

[thesteve]

jumper is fine, once your sure your jumpering the right point
what i like to do is push a wire through the bad via and solder both sides

[Zer0-2k11]

Steve, your a miracle worker!, that was it. Thank you, the sounds working with HuCards

But i got no audio with Far East of Eden except the sound when a dialog pops up just after i press the  run button. Cant get past that dialog but i think i just need to tune the pots a bit more

[Kid Compile]

Sorry for the strange first post - I used post a little bit on an older version of the board back around 2005, my username then was Kakizaki, but for whatever reason that account doesn't work any longer. I suspect due to inactivity.

Anyway, my TurboDuo is starting to falter here and there, mainly sound issues and I suspect it is probably due to bad caps based on everything I have read both here and elsewhere. I am also getting a bit nervous about my lens as the poor guy seems to hang up or take an excessively long time to load CD games.

I've noticed that a few members here repair systems but I didn't want to PM anyone out of the blue without posting first.

I was also looking for a little advice. I was really pretty bummed when this first started happening, and was looking to replace my Duo rather quickly (one of my favorite systems), especially since I made a point of picking up a few extra PC Engine games the last time I was in Japan earlier this year.  I also thought it might be an excuse to snag a Duo R or RX. They just look so damn rad. I was on the cusp of snagging a modded Duo RX from Doujindance on Ebay, but after reading some posts here, I am not so sure anymore. Should I steer clear of Doujindance and try and find someone else to just repair my TurboDuo? I wouldn't mind a region mod, but it isn't a necessity for me right now. I also have a CoreGrafx that I use to play HuCards.

Thanks for the input!

[raylyd]

i just fixed one i had to remove the amp had capacitor fluid all over the chip and cleaned the pcb all works fine now

[Nicktendowii]

Hi, my problem is slightly different, was wondering if it would be the same fix? It's not that the sound is scrambled or doesn't play at all it's just extremely quiet, whether plugged into the headphone socket or direct from the composite cables. The audio on CD games, especially music, is even quieter still. It also produced some static sound as the TV needs to be turned up to full volume to (just about) hear anything..

Any thoughts? Also it's a PC-Engine Duo I'm using. Got it cheap second hand in Japan. Bought the wires separately and they may be Megadrive 1 cables.. Not sure.

Thanks for the help! And as this is my first post, I hope to be posting more in other topics!

[thesteve]

sounds like the normal cap issues

[Nicktendowii]

sounds like the normal cap issues

Thanks, just wanted to make sure before going ahead with the fix

[levesque0999]

thats wonderfull. I just sent my pc-engine to my repair guy with that sheet. It wont be a problem for him . I can repair game boy cartridge battery but i use duckt tape .. for soldering i prefer give it to a pro

[SegaSonic91]

I finally got my junky PCE DUO finished recapping yesterday.  The AC adaptor finally arrived so I was able to test it, at last.  I had no sound when I first turned it on with PAC-LAND in the system.  Hmmm, ok, "I'll test out the CD drive", I thought.  It worked!  Loaded DOWNLOAD 2 with no issues, but still no sound.  I thought that maybe the new caps need to charge up for a while before the sound comes back.  That worked and I had full Hu and CD sound after a good 45mins-1hr. 

I thought I would check this morning to see if it was still working and when I turned it on again, there was no sound   This time, however, sound popped in after about 10mins.  Does it need a long time to charge?  I am letting it sit for a few hours today in the hopes that it will full charge and I'll have no more issues in that area.

EDIT:  Hmmm, well that did not work.  I just checked it and it had no sound again.  I checked the caps to make sure they were OK and discovered that I actually had a cap missing, duh.  Guess I will have to try again after rectifying that later today.

[thesteve]

you have an open via behind the heatsinks, near the 10uf caps

[SegaSonic91]

Thanks, I will take a look and see if I can find it.  I just remembered that I also did not change the electrolytic caps around the heat sink because I was having such a hard time getting them free.  I thought of clipping them off and trying to remove the legs, but decided against it.  It was trying to get the bent bit of the leg from underneath the board to come free that was the problem.

I am happy to say that I had no problems with RGB amp installation on this system.  Tested it yesterday on my wonky French Trinitron, and it was gorgeous.

[jlued686]

Just wanted to give this guide a big thumbs up. My son and I did this fix last week and my Duo sounds fantastic! Thanks D-Lite!

[Abelardo]

Hello everyone, new old member here, recently got into modding systems an I ran across a pc engine duo that needed a recap (or so I thought), ordered cap kit from console5 and proceeded to do my first recap job, took me a long time so I was happy when I was done, but unfortunately CD audio didn't work, if I turn the volume up all I hear is static noise and some ocasional cracking, hucard  audio however is loud and clear. The only thing I'd notice is using 4.7uf 50v caps instead of 16 or 25v ones, console5 sent me the wrong ones and apologetic he was going to send me replacements, but since I'm in Mexico I opted to get them locally, so 50v was the only one I could find.

It's been days already since I've been trying to get it working, I've reseated some caps and I'm sure they're all fitted correctly (no shorts, continuity is there to where they're supposed to go, etc), so now mi conclusion is that there must be a damaged component or trace somewhere, after reading all this thread I found out about the audio diagrams Charlie posted, I'm looking at the TurboDuo Audio Multiplexer diagram, since hucard audio works I'm assuming the problem lies at AVC (u505) or at some point before that, am I correct? All 4558 and 4560 ICs that faced upward had normal voltage apparently, well some 4558 had voltage closer to 7 at pin 8 instead of 8 but I think that's normal, one of the voltage divisors is providing 7v so that's got to be the reason (my ac adaptor provides 9v instead of 10).

Sorry for the lengthy post, it has been more challenging than I expected, I welcome any ideas any of you guys might have, hopefull I can get this thing to work, thank you everyone!

[Keith Courage]

crackling means there could possibly be some bad traces to some of the caps, old cap goop in some of the via holes, or goop underneath some of the 4558 Op amps.

I always remove two of the the 4558 op amps every recap job I perform, clean under them really well, and then reinstall. The two to check would be the one closest the the AV jack next to the two 10UF caps and also do the same for the 4558 op amp that is on the bottom side of the board near the Oki5205 chip.

[Abelardo]

crackling means there could possibly be some bad traces to some of the caps, old cap goop in some of the via holes, or goop underneath some of the 4558 Op amps.

I always remove two of the the 4558 op amps every recap job I perform, clean under them really well, and then reinstall. The two to check would be the one closest the the AV jack next to the two 10UF caps and also do the same for the 4558 op amp that is on the bottom side of the board near the Oki5205 chip.

Thanks! I'll try that, let me see if I can get back to it tomorrow, man who would've though cap goop would cause such havoc, so in theory it's shorting the 4558's? haven't checked the one in the underside for shorts now that think of it, I'll try to remove them but if I find it difficult then at least I'll reflow them.

I've cleaned the board thoroughly with water, soap and a soft brush (that's what I do with arcade boards), sadly things didn't improve after it dried, how can you get cap goop out of the vias? A toothpick for the big ones but would that also work in the small ones? I'm also unsure how can it affect the via, is it shorting the via with the stuff around it?

I almost forgot that I took some photos the other day, looking at them I could've done a better job cleaning the flux I used, and some of my solder job looks sloppy, but aside from that is there something that looks troublesome? Here are the pics: https://imgur.com/a/N7sPh

Thanks again Keith!

[Keith Courage]

If all checks well with the op amps that I mentioned then you should then move onto checking the positive end of the 22uf cap near the AV jack and then also the 22uf cap near the oki5205 chip. Bot of those pads can get damaged from the old caps and sometimes require wires to bridge the damaged traces.

[Abelardo]

I give it a try yesterday, removed de op amp near the power jack and pulled a trace in the process but I was able to fit in a jump wire so still haven't managed to ruin it 

Checked the caps you mentioned, they seemed ok, not shorted and continuity was there, I thought about reflowing all the op amps and I did, but no improvements, so then I took a break and watched one of the longer duo repair videos on YouTube, the guy actually had problems after recapping and turns out a couple of VIAs had failed on his duo, the VIAs in my duo didn't looked that bad so didn't thought the problem would be there but with nothing else working I gave it a try, took me a while but actually found one that failed the continuity test! It was a small one and it's purpose was to ground one of the underside op amps, fixed it and the cracking is gone! Still no CD sound but I'm glad there's some progress after being stuck for a few days.

I'll check for more VIAs today, thanks for all the help Keith I feel that I'm getting very close 

[Abelardo]

Found one more broken VIA, fixed it and CD audio is back! I almost gave up, thank you Keith for giving me new things to check and keep my hopes up, one more Duo saved

[NecroPhile]

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.
https://imgur.com/a/rqyZn

Turbo Duo Board

[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.
https://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.