Found a broken Duo

[SamIAm]

Hey guys. I picked up a broken Japanese Duo for 2500 yen, and I'd like to try my hand at fixing it.

The Hucard side works completely. A side by side comparison with my Supergrafx shows weaker sound output. The disc drive will spin a disc and the busy light will turn on, but it won't load any games. I'm not sure if the lens actually moves.

I don't have the screwdriver necessary to open it, so I can't say what the internal situation looks like, but at least the screwdriver is in the mail. I've already looked up places where I can get cheap capacitors online in Japan, too.

Right now, one question I can ask is about how the drive on a properly working Duo spins up a disc. I have a Duo-RX that barely makes any noise and seemingly goes from zero to max speed in just a couple of seconds, but when this broken Duo is spinning up, it distinctly takes a few seconds longer and the motor is more audible. Is this normal?

[Fidde_se]

Leaking capacitors around the audio amps are the fault for the drop in volume to begin with....

[Keith Courage]

the lens motors in those things can be noisy. That is completely normal. however, sometimes this can be a sign that the lens motor is going bad but that is rarely the case.

[SamIAm]

Thanks for your replies.

What about the CD turntable motor itself? Do those ever go bad? That's the part that sounds like it might be struggling.

[Keith Courage]

I've never seen a dead spindle motor. If it sounds funny at all when spinning that could mean 3 things, Bad CD lens, Bad CD drive capacitors, or a need for potentiometer adjustment. Also, are you testing with CDRs? CDR discs usually make the lens whine louder when a CD is spinning.

[SamIAm]

That's great info.

I tested a genuine game and a pressed audio CD, and the results were identical.

Well, the next step for me is to open the system up and replace the capacitors. I'll get back to you guys as soon as I do!

[SamIAm]

I finally got the sucker open.

There doesn't seem to be much in the way of visibly deteriorated capacitors, but I still plan on replacing all of them.

The alarming thing is that OKI M5205 chip, which sits to the left of the laser motor, seems to have leaked something itself. Searching the forum shows that others have had this chip fail on them, so I think it's safe to say that I'll need to replace this as well.

Another thing that shows signs of leakage is the 21.4MHz oscillator. What does this operate?

And finally there's a little thing marked 5.5V sticking up that I would guess is the save battery. Well, it's got leakage around it too, but save functionality still works. Or at least it worked for the five minutes I shut the system off after making saves in Neutopia.

It's a lot to work on, but if I can get the parts, I'll happily take a crack at it.

[Fidde_se]

The M5205 is the ADPCM voice chip, it has nothing in it that can leak, it has a few capacitors around it that can and are very common to leak giving very low volume in voices and certain fx sounds, only affects cd games should be noted.

[SamIAm]

I know it sounds incredible, but I'm pretty sure that something came out of that chip. Bearing in mind that it's a couple of millimeters above the PCB and the goo could hardly have climbed up it, you can see how something came out of the two halves of the black plastic casing like melted cheese from a sandwich. It covered the middle legs of the chip completely. And there's a puddle of the stuff under the chip that doesn't quite extend to the two caps next to the chip.

The STC chip inside Dai Kaiju Monogatari 2 for SFC is known to go bad and leak stuff as the battery dies. I've seen that first hand. This is fairly similar. I'm not sure what it is, but something is in the chip, I think.

Anyway, as I look at the bottom of the PCB, I can see all kinds of goo. This definitely needs a full capacitor replacement. I'd be surprised if that crystal oscillator wasn't borked as well.

A good source for all the necessary capacitors in Japan continues to elude me, however. Currently it appears I'll have to buy from a few different places and take a hit on shipping. If anyone has extras to send, I'd be willing to work out a trade for something from Japan.

[Fidde_se]

The timekeeper IC in CDi:s have batteries in them too, but this one is as dry as a desert, a silicon chip bonded to the legs and pressed into a plastic body.



It's more likely it's flux of some kind being dropped or even sprayed up or foamed up during the wave soldering process traveling up the legs as it goes threw the heating stage or even the solderwave itself.

Touching it with the tip of the solder iron would melt it, electrolytic fluid smells like old fish...

[Fidde_se]

gamedoctorhk has the on his site too
http://gamedoctorhk.com/index.php?main_page=product_info&products_id=1143

[SamIAm]

Thing is, the STC chip is powered by an external battery as well.

Don't get me wrong, I know I could be totally off, but at a glance I think anyone would conclude that something had come out of the chip itself. It's like the Space Jockey in Alien or something.

Anyway, maybe I'll see about ordering one of these sets. I can get a complete set in here Japan with lots of spares for about $30. Is it easy to accidentally destroy a capacitor while working with it as a clumsy noob?

[thesteve]

neither the adpcm or the backup cap can leak
the goo however is formed by power running through the leakage, so will be most evident where +5 and ground run close without any coating