PCE Duo - No Sound *solved*

[HuMan]

I bought one of these and installed it myself. It went very well, not a single ripped solder pad.

https://console5.com/store/nec-turbo-duo-pc-engine-duo-smd-cap-kit.html

[YoshiKnuckles]

HuMan, you can still get to those caps. It's just a bit tricky.

The chip should be a SIP package and you should be able to stand it up, remove the tape and get to the capacitors. Then just put the tape back and bend the chip back down after you replace the caps.

[HuMan]

I don't want to risk breaking the pins on that SIP IC. I could desolder it but, really, what difference would 2 leaded caps make?

In other news, I also took the time to recap my white PC Engine, hopefully it'll keep going for another 30 years (almost 30, PCE turns 30 next year).

[Keith Courage]

you can change those two capacitors from up above but you honestly don't need to. Those two capacitors have nothing to do with the audio issues you are having.

[HuMan]

Good news everyone! I believe I have found the source of the voltage drop - by accident.

R306. When I was checking voltages, I accidentally touched R306 to that nearby power cap, which effectively bypassed that resistor. Doing that brought the audio back nice and loud. Both the AV port and the headphone jack, I only tested with a HuCard game.

Someone with a working Duo, please check the resistance of R306, I'd like to replace it. Also wattage if possible, most of mine are 1/4w, not sure if that's acceptable. I have a few bigger ones though.

EDIT: Yes, I also replaced those two 100uF 16v caps under the SIP package chip. The entire Console5 cap kit has now been applied.

[mickcris]

What is the code on the resistor.  It's kind of blurry so  can't make it out.  You would need to remove it to measure so it's easier to just match it up with the value on it.  It also looks to be at least 1206 size which would be 1/4 watt

i forgot i had one half pulled apart.  it says 202 on it so it is a 2k ohm resistor.  also the size is 1210 so its a 1/2 or 1/4 watt resistor.

[HuMan]

It's got "202" written on it. I did try to get a resistance value but it doesn't stay consistent. I don't have any smd resistors, or at least probably not correct ones.

[mickcris]

It's got "202" written on it. I did try to get a resistance value but it doesn't stay consistent. I don't have any smd resistors, or at least probably not correct ones.

i edited my post above.  its a 2k ohm 1/4 or 1/2 watt resistor.

edit:
the first site i looked at said 1210 was 1/2 watt but most others say 1/4 watt.  better to use a 1/2 watt just to be safe though.

[HuMan]

Ok, compared to my previous fixes, this one kinda sucks, but I don't have anything close to "2k ohm 1/2w resistor", I'll have to buy that at a later time. I have 2k resistors but they're 1/8w. For now, I stuck a 600 ohm resistor in there - I won't play the Duo much for now until then. It's bad but the sound finally works now. AV port, headphone jack, HuCard and CDs, it all works.

I also did one more voltage check. The caps are at 3v, op amps are at 6.2v. Still a bit low, will probably be improved further with a correct resistor.

For posterity: Fixes made were patching corroded vias at the 22uF 16v cap near the super cap, at the 4.7uF cap at the volume wheel and lastly the 2k ohm resistor near a 330uF cap under the board.





(pretend you can hear Bomberman 94 playing triumphantly)


Thanks everyone for helping to resurrect my Duo!

[mickcris]

It's a 2k ohm not 20k ohm.

[HuMan]

... *sigh*, at least it's just text I get stuff wrong in. I'd like to hope that never happened with my Duo.

Still, YAY I got my Duo working!! Thank you to everyone who pitched in to help with the repair!

[Necromancer]

Well done! 

It's always nice to hear when someone gets a system back to playin'.

[crispytreat]

This thread was a great help to me as well.  I was finally able to get my Duo up and running with full audio, HuCard and CD.  My issue was related to the transistor that is near pin 1 of IC505.  It appears it is supposed to convert the 12V to 8V but one leg was only outputting 1.6V so I assume it was bad.

I just jumped from the good leg and everything started working after cleaning up a few vias.

I need help with sourcing a replacement part for that transistor.  I am not the electronically inclined, so if someone could help that would be greatly appreciated.

I am not sure if it is ok to ask this here or if I should start a new thread.

Thanks