Planning to do some surgery on a Japanese PCE Duo very soon

[pooyan]

I plan to do a RGB mod and a sound fix on my Japanese PCE duo, and today I bought all necessary parts, including a nice DIN 8 plug which will be mounted in the PCE case.

However, I still am unsure about a few things which first have to be cleared. When the RGB mod is done I want to connect the PCE Duo via a homemade RGB scart cable to a TV which accepts RGB scart input. I know I need to make a RGB amplifier, and that I have to get RGB directly from the chip. But:
1. bearing in mind that I will connect via scart to a TV, do I have to lead composite sync also through the RGB amplifier, or can I just tap composite video from the original 5 pin AV output and lead it directly to the scart cable (I suppose a TV uses composite video instead of composite sync)?
2. I know I can tap ground, +5V and composite video from the original AV ouput, but are there perhaps other, better places to get it from?
3. According the RGB amplifier schema I use, the left and right sound channel signals need to go to a 10uF capacitor each. Why is that?

I hope someone can help me with the answers, and in the meanwhile I will keep myself busy by adding a 50-60 Hz switch an a lockout switch to my PAL SNES 

[Ravij]

I'd been interested to know how this goes!

What circuit are you using for the RGB amp? Is it using an existing chip/video encoder or is it going to be discrete transistors?

[pooyan]

I'll keep you informed. I use the RGB amplifier circuit on this page http://www.gamesx.com/rgbadd/duorgb.php

[pooyan]

Today I exchanged some capacitors which are all loacted above the two heat sinks of my PCE Duo with new ones (all 50V): 4X10uF, 2x22uF and 2x47uF. I also replaced the remaining two original 10uF caps on the board. After this the sound quality improved a lot, I had game music again in my CD games, although with some soundglitches. However, after an hour or so the glitches became more present and a short time later all in-game music was gone on all CD games (as it was before the caps exchange).  Only the sound effects are still there. Luckily my Hucard games do play with sound and effects.

I examined the PCB again for more bad capacitors, and I noticed one more bad one, a 22uF located at the top center of the PCB. Unfortunately I'm out of caps, so I have to get me some more. This can take a while because I don't live nearby an electronics shop (Internet is a no for such small order).
I also decided that if I still have no good CD sound after replacing this remainign 22uF cap, I will try the dishwasher procedure.

I first want to have sound OK, before I go on with my RGB mod. Oh, and the mods on my SNES went allright, I now have beautiful 60Hz pictures on my PAL SNES.

[pooyan]

Yesterday I replaced another few caps in order to solve my sound problem with the PCE Duo. Unfortunately it didn't work. On the contrary, now I had no sound at all anymore, not from CD games, not from hucard games, not from the AV and not from the Headphone out. It doesn't matter how high the volume is set, I hear nothing, even no static noise. In the attachment I marked the 18 caps I replaced with a blue sign. I double checked all replaces caps on shortcircuit etc., and they are all soldered in the right way. Most replaced caps are 50V, a few are 35V and 63V.

What the heck, I thought, and I threw the PCB in the diswasher (I mean, it can't get more worse). I gave it a nice and warm (50 degrees Celcius) soap bath for 90 minutes. I have to say it came out very clean and I got hope again. I dried it for 24 hours (the last hour in the kitchen oven which I heated to 50 degrees Celcius (I mean, it can't get more worse) and I assembled the PCE Duo again.

I have to say it was a scary moment turning the power on, but nothing bad happened. The PCE Duo still works OK with regard to the Hucard en CD Games. But there is still NO sound at all.

Now I am lost and I hope someone has another idea or even better, a solution. I would hate it if I have to throw the PCE Duo in the carbage bin (don't want to spend another dime on it).

[Necromancer]

That blows herpes infected hermaphroditic goats!  Don't chuck it in the dust bin just yet; you more than likely just need to replace a few more caps.  I understand not wanting to sink any more dough into it, but replacing the rest of the 'em will still be cheaper than buying another Duo, which will eventually have the exact same problem anyway (unless the caps have already been swapped).  Best of luck to ya.

[Michael Helgeson]

Double check your solder work,and also if you have a meter maybe the caps themselves. Although rare you can get new caps that are bad. Make sure you have the polarity position correct too.

[Duo_R]

I just noticed that your cap values look different than this photo:




I see you have a yellow for the 10uf caps, but I don't see it anywhere on the image you attached. Also, what voltages did you go with?

[pooyan]

I did use tis image. I replaced ALL but one of the caps you see in this picture (and more) with caps with the same uF value ( I double checked). The one I didn't replace yet is the 100uF 10V.

The caps I used range in voltage from 35V to 63V.

[Duo_R]

Pooyan, did you replace the 100uf, 1000uf, 470uf, 330uf? I had bad ones in my Duo. I have replaced almost all the caps, and running a dishwash tonight. I wonder if I should replace the 3.3uf? I have a spare one so I might if it doesn't fix.