REPAIR GUIDE - TurboDuo: Sound Fix

[BlueBMW]

Since you have a Duo system you just need an Arcade Card Duo.  The Pro cards are for systems that don't already have system 3.0 built in.

Look over this compatibility guide for some more information on this subject:

http://pcenginefx.com/main/nec_compatibility_guide.html

Region mod info can be found in this thread:

http://www.pcenginefx.com/forums/index.php?topic=10112.0


Also, you should be able to find an Arcade Card Pro for less than $80.. that seems like the top of end of what it should cost.  An Arcade Card Duo can probably be had for closer to $30-$40.

[Mystery]

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 (http://www.pcenginefx.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?

[thesteve]

could be a bad amp, or a bad connection
check the reference voltages (inputs) on the affected amp, odds are either the - inputs are high or the + inputs are low

[michichan]

Hi, and thanks already for all the wonderful maps, schematics, and videos I've seen from everyone!

I'm attempting to replace several caps (I don't have the time or money for a full replacement right now, so I'm just hitting the bad ones) and I've gotten them all off the board without any damage EXCEPT for C323. For some reason (probably corrosion) the trace just came right off the board, and I'm guessing I'm gonna have to use a wire now. However, I'm having trouble figuring out the path, since it seems to have two? I read somewhere that C323 has a second source? If someone could help me figure out where I need to solder this wire, I should be able to get everything rolling. Thanks! (If you need a picture, I can get one)

[Fidde_se]

Well C323, the minus side connects to the ground, which can be connected a little here and there, and the plus side goes to leg 3 of IC506 (4558).

[michichan]

Ah, ok! Only the plus side came off, so if I just run a trace wire to the IC's 3rd leg, I'm all good?

[Fidde_se]

Thats correct

[Everblue]

Not sure is this is related but I will have a go:


I just bought a brand new old stock white PC Engine (the very first model) along with an AV Adapter for it as sold here:

http://www.otakus-store.net/en/nec-pc-engine/155-nec-rgb-av-box-for-nec-pc-engine-console.html

It works great but audio volume is around 40% too low, no distortion or anything....

Anyone knows if this is a case of the capacitors needing replacement, or audio from a white PCE's expansion port is too low? I have confirmed with the maker of the AV adapter that it doesn't come with an audio amp.

Any help is appreciated

Thanks!

[michichan]

So I've been working on the capacitors, but I've got a problem where the audio has a lot of electronic static noise when you turn on the system, and then sometimes CD audio will play for a moment and then the whole system audio just kinda dies. Nothing seems to be crossed or short circuited, and I've redone several solders, but it just keeps happening. Any clue? And if there's not a clue, I'll probably just have to send it off...but I don't wanna admit defeat yet!

[BlueBMW]

How much cleaning did you do once the caps were removed?  Often the fluid gets on everything and will cause static / shorts.  Be sure to check around the amp chips on the backside of the board too.  Look for any vias or traces that have turned black.

[blueraven]

Make sure that the trace wire you installed has a solid connection. I had the exact same problem with my primary unit a year or so ago, and it turned out to be a bad connection from the wire to the IC, and it "popped" off like you described. Also, like BMW said, use a toothbrush and cleaner to get the grime off of the trouble areas, and remove any unnecessary flux. You did use flux on the wire?

[michichan]

I did use flux, and I did do quite a lot of cleaning, but not on the underside. I'll try that and also try redoing the line to the IC. Hopefully one of those will work...

[thesteve]

if all  sound is fading in or out, it could be a missing voltage to the amp by the AV plug
had one here that had no sound for the first few min, then would crackle to life.
found an open via feeding a ref voltage to that amp.
the amp would generate the voltage after some time, masking the issue

[kisaku]

hello, i have a sound problem with duo. when i start it, it is all ok, but after about 5 MINUTES the audio fades in and out... i replaces the post op amp, but nothing changed... should i change other caps? or is it a laser problem?

[thesteve]

Laser issues will cause only cd sound to drop, if chip sounds fade its not cd related

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