[PC Engine Duo] Missing parts.

[crossmanbx]

Hello,

I've just ordered a duo via Ebay, and received this one from Japan.

Seller described it as no sound and no cd working only.

After opening it, the backplate under the mainboard is missing, and several wires are cutted.

Some caps are already changed. And there is no front plate too. Hucard are ok, with no sound like expected.

Is the backplate missing a "no go" for the repairing ?

Should I contact the seller about these problems ?

Thank you and sorry for my poor english

[soop]

The backplate provides some RF Shielding, and ground to several points on the board.  As long as you ground these points, you can still use a system without the plate.

also, if the hucards work, that means the system is fixable.  You probably need to replace some more caps, or fix traces for the sound, and then work on the CD side, if you know what you're doing.

[crossmanbx]

Thank you soop for your answer.

I'm going to repair this duo without the backplate so, and i will ground the other points.

I'll change all the caps too, and, little question, for cleaning cap leakage, what is the best solution, water or isopropylic alcohol ? Nobody says the same thing on the net.

[soop]

Thank you soop for your answer.

I'm going to repair this duo without the backplate so, and i will ground the other points.

I'll change all the caps too, and, little question, for cleaning cap leakage, what is the best solution, water or isopropylic alcohol ? Nobody says the same thing on the net.

if you're doing it at home, I'm pretty sure the best option is to use rosin flux over the entire affected area, then activate it with a heat source.  If you don't have a hot air attachment for your station (mine has one and it was £30!) you could try picking up a heat gun, but if it's not variable temprature, be careful not to overheat the board or components.  The board can crack imperceptibly if it's heated too high or too quickly.

Once the flux activates, it should take away most of the crap, and you can then clean the flux away with isopropyl alcohol.

You'll want to do the cleaning after you've removed all the caps, and removed the old solder from the pads (the old solder won't be any good for the new components.

*edit*  Here's a video that should help you:

The guy does everything textbook, but as other people have said, he does have a very expensive setup.

[NecroPhile]

I'm not smart enough to fix stuff myself, so I'm no help there.  I'm just here to say welcome aboard! and I hope you get 'er working 100% soon.  Good luck!

[crossmanbx]

Thank you too Necromancer !

Today i've spent 2 hours to decaps and to remove old solder.

Tomorrow, i will try to clean the board. I think it's going to be a hard trick, I will see at work if we have isopropylic alcohol.

I'm a bit afraid with Rosin flux, do you think it's really necessary soop ?

By the way, two solder pads are gone out due to soldering iron ! Much better with cutting pliers, at least for me ! It sucks a lot ...

[Cordelay]

May those pads rest in peace. 
Patience and good luck repairing them!
Hope it all goes well.

[soop]

Rosin flux is nothing to be afraid of, it's just a mild acid.  Best to make sure the area is well ventilated though, the fumes aren't good for you.

Incidentally, rosin flux is inside of electrical solder; it's actually a hollow tube, and the flux inside is released onto a component as you heat the solder, destroying (at least part of) the layer of oxidisation, and allowing a proper bond between the solder and component.

Isopropyl alcohol might not be enough to clean the board on its own, but you can try

[crossmanbx]

Today, i've successfully cleaned, I hope, the board with IPA. I left soaked it completely for 3 hours, and thanks to the brush, it looks like new. On the other hand, serial number is gone.  . I've got a picture, and will rewrite it on the pcb.



This evening, i'll try to solder again a few caps.

@++

[soop]

Wow, great job!

Keep us updated please

What caps are you gonna put on there?

[crossmanbx]

Ok, it's done !
All caps soldered again !
I've grounded all the needed points too, i hope it will do the job.


4K: 180419050757568874.jpg


4K: 180419050800358092.jpg

But still no sound when i power on the duo (A little bit with jack out)
Very dissapointed.

And i begin to read again some post on this forum, and Slypty give me the solution (big thank you to him !).

Sound solved!  Sorta 

  By connecting the 2nd leg on the Op Amp (counting from the right, bottom as 1), I  noticed it would come to life by touching it or bridging it to positive output on caps.  So, I attached a wire to it and probed for a consistent audio feedback, and came to C322 as the culprit.  I just soldered the wire to the C322 positive out, finding the exact trace seems like a lot of work.

I will post a picture later.

Now, i can't continue to repair cd chapter, cause i don't have yet a controller, it is on the road...
Is it possible to simulate the "RUN" button, with a trick, to pass the "super cd rom2 screen", so i could see what happens next ?

Thank you !

[crossmanbx]

OK, controller received. 

Finally, i can push "RUN" ! ;) 

No cd spinning but after hack (lens was stuck so i have to remove and lubricate all what i could, it's okay. No problem with Audio-cd.

I don't own original cd games, so i burn a few iso on cdr.
Sadly, no way to launch only one game.

After playing a while with VR102 and VR104, dracula X is starting. Very cool.

But sometimes, cd player doesn't start, and I don't know why. No "Busy" light on, no lens focusing, no movement, no sound from the cd player. Screen displays "Wait a moment" and nothing after, system is idling. I have to turn OFF the duo and wait for a time. Sometimes 15 minutes, sometimes 2-3 hours, and everything works again.

Do you have an idea ? Thank you

[soop]

Great job, I'm really impressed that you figured so much out just by reading around!

The warm-up issue does ring some bells, but I can't remember the solution.  Off the top of my head:

could be a cold solder joint
could be a pad lifting
Could be that the back plate was actually providing some heat disipation as well as ground.

Probably the easiest thing to start with, if possible, is to try the unit without case, and some kind of active cooling, like a fan, or even try refrigerating it and see if that reduces the "reset time".

[crossmanbx]

Thank you soop !!! But when i was young, i already used to mod 50hz system to 60hz !
Very interesting stuffs !

I have a problem with ADPCM too. Troubleshooting coming ! ;)

[senkun]

I love this thread! Inspiring to see patience, tenacity and knowledge at work. I would have given up seeing that board in that butchered state, but crossmanbx never said never and revived it to such a beautiful current state. I have no doubts once he's done it would be 100% again.

[crossmanbx]

Ok, i have found why ADPCM was dead.

IC503 was not grounding on pin 4. While looking closer, via near pin 5 of IC503 was corroded, that's why IC503 was not working.

So i put an electrical cable into the via and soldered each side of the pcb. It' s not pretty to see but it works. By the way, this stuff solved my main audio problem, i can now desolder Slipty's trick !

All audio problems were ground related, at least for me.



Thanks to the guy for these two diagram, I found them on this wonderful forum :

Abbreviated schematic of DUO audio circuitry, part 2:


Abbreviated schematic of DUO audio circuitry, part 1:

They are very useful !

After that, I took a second look to other vias, next to the cd side of the Duo.  I had to repair 2 others the same way.
CD works 100% now, just fine !

I'm waiting now for a RGB mod, and i have to 3d print an Hucard door cover too ! Mine was missing.

Thank you everybody for all your advices.

[soop]

Hey, well done!!  And thanks for posting the solution!  One more duo saved from the scrap heap ^_^