2 "broken" arcade PCBs

[ken_cinder]

Ok, here's the deal, I have 2 "broken" arcade PCBs.

1 is an original Double Dragon Jamma PCB, and the problem appears to be a background layer. It appears to be corrupted, as it displays 1: The wrong colors 2: garbled graphics.

The second, is a Taito F3, running Puzzle Bobble 2. Some character sprites and other things appear to be garbled. I don't have another cart to test and see if it's the motherboard, or the game cart.

What should I be starting to check on these boards? Chips containing this data, how would I check them? Since all tests are passed on starting up these boards, including checksum checks, would that indicate the roms etc are fine, and it's a component problem, like a capacitor/resistor etc somewhere?

[l_oliveira]

honestly like 60% of arcade board faults are related to printed circuit board corrosion.
You will have a hard time tracking the signals down, but if you do it as hobby it won't be too painful.

I use o-scope to follow broken tracks on arcade boards, but you can try to use your own finger. All you have to do is run the game board and
try touching the pins of the ICs related to the graphics. If a track is broken somewhere, touching will cause the graphics to change. It's just a matter of figure out which pin of which chip is loose and repair the broken copper track.

Good luck

[ken_cinder]

Thanks , but I'm pretty sure these are both "shorts".
There is no corrosion on my boards, these are both my own fault in being clumsy (Both years apart from eachother) and knocking a board placed poorly, into something else.

I checked the DD board out for damaged traces after knocking it over, and there weren't any. The traces on that board are huge too, nothing tiny and easily damaged and unseen under a microscope (Or with the naked eye for that matter).

[l_oliveira]

Then next step is check the SMD QFP (Quad Flat Pack) chips for bent pins touching their neighbour pins.
That's common on boards that were stored in boxes without proper protection.

[ken_cinder]

I just tried to get back to trying to fix my Taito F3. I checked all the resistors, diodes and capacitors on the motherboard and the game cartridge and they all seemed fine.

Unfortunately, this thing doesn't have a test menu function to check the roms, so I can't do that. And the board boots up fine so it must do those checks on it's own (There is a 5 second wait on boot, but it's not verbose)

I think I'm going to have to resort to your finger technique and if that doesn't work........I dunno.

Edit: Nope, I can't trigger anything odd that way. Here's a picture of the problem. I get the feeling the data on a ROM/ROM(s) is corrupt, but I don't know how I'd find it.

[ken_cinder]

After alot of bullsh*t and tinkering, I managed to pinpoint the sprite roms as the problem. Thanks to the MAME source for taito_f3.

I then spent some time ripping the source tree apart, so I was left with nothing but the F3 drivers and related. I then marked the eproms for my game as "NO_DUMP" so MAME would not audit them, renamed the E10-01 rom..........and lookey here!



The same problem I have on the real hardware (Almost, I think I may have a bad tile PROM too).

Hooray for MAME! Too bad I'm ready to throw my Double Dragon board at the wall. MAME driver is no help, WTF kind of naming scheme is 21j3-1.rom? Theres no chips named anything like that on DD boards and there are over 100 freaking chips on this 2 PCB game.

[ken_cinder]

Well I managed to diagnose the F3 myself, the Double Dragon I'm not so lucky since it's a bootleg that has (most likely) scrambled GFX ROMs.
I can't do the same thing as I did with the F3 to figure it out, because MAME can't even run those particular bootlegs.

But the LAST thing in the world I would have ever expected happened.

TheGuru offered to repair my board for me. This guy is very busy with the MAME dumping/decapping projects, and he offers to repair my crappy bootleg board for me?
Amazing......the world isn't going to hell in a handbag after all it seems.

[l_oliveira]

Of course ! Your board is going to be dumped and analyzed in the process and that's ... well...  what he does...

Glad to hear that you were able to figure out your own solution for this problem. I bet most MAME users don't even remember (or know) that MAME original purpose was aid on repairs of old boards... Exactly what you did.

[ken_cinder]

No, it's your common bootleg board with the ROMs doubled up on half the number. He has no interest in dumping it, he just offered to repair it when he gets the time.

I didn't take him up on the offer, the shipping back and forth etc would not be worth it. Selling the board on Ebay, maybe someone who can fix it buys it.