CPS-1 motherboard and game board repairs?

iatneH · Post by **iatneH** » Tue Jun 27, 2006 9:42 pm

I brought home a doubly dead CPS-1 set today which I pinched for free...

The motherboard (when tested with a known working game board) outputs some scrambled-ish graphics, and appears to be missing some sprite/bg layers as well.
The mobo is one of the larger old versions (the one that's about the same size as a CPS-2).

The game board is a Carrier Air Wing, and is completely knackered from what I can tell, but I basically haven't had any experience with CPS-1 stuff. It won't boot at all on a known working motherboard, I just get a black screen. I don't know if it's missing some ROM chips, or if the software board is genuinely dead.

Anybody seen these symptoms, and know how to repair them? Thanks.

Also, what about a CPS-1 motherboard that works fine but has no sound? I might end up with one of those later too...

edit: OK, I've looked at the cawing.zip romset and it looks like all the necessary EPROMs are present and in their correct slots. What could it be??? Also, still couldn't find anything about fixing the mobo...

edit2: I also noticed on the Carrier Air Wing board that EPROMs 18 and 19 are missing their stickers, so there is this clear window visible. EPROM 36 also has the sticker partially peeled. Could the chips have been erased accidentally from light exposure during this time?
If this is the cause of the problem, could it be fixed by burning an EEPROM with the appropriate file, and fitting it in the board?

Stefan_L · Post by **Stefan_L** » Wed Jun 28, 2006 10:54 pm

Here is a pic of my Carrier Airwing, maybe you could compare and see if you PCB is missing some parts? PAL's or resistors and such.
Carrier Air Wing PCB pic

iatneH · Post by **iatneH** » Wed Jun 28, 2006 11:12 pm

Thanks for the pic Stefan, everything seems to match (except my stickers say CAU). Two of my EPROMS don't have the sticker, so I *suspect* that they got erased from light exposure, but I have no way to test it unless I can get a working motherboard and an EPROM burner.

Actually, I have another question.

Anybody know what CPS-1 games have interchangeable C-boards? And are conversions as simple as burning EEPROMs from a downloaded romset and replacing the chips on the B-board? I'm just curious because I came across a CPS-1 set with a C-board labeled as Mercs, but the game was booting up as Sangokushi.

Might be nice if I could get a couple of cheap Street Fighter IIs or something and just swap out the chips for Varth and Area 88 (for personal use, of course! Not for resale profit)

Post by **system11** » Wed Jun 28, 2006 11:56 pm

All CPS1 boards are not created equal. Some of them actually have more ram than others... Also, there are a couple of PALs that may vary between game or board revision - never worked out which matters to which, but I did find that Carrier Airwing would run on some boards and not others - had one with a toasted mainboard myself.

To repair mainboard: Check all the solder joins where the four interconnects are - these frequently fracture. Reseat any socketed chips, past that you're pretty much screwed unless you want to learn how to use a logic probe. Even then it's no fun, believe me - I've done this

What you've described sounds RAM or ROM addressing related, and might just be the point above about not all being equal..

As for the B+C pair, you really will need to verify all the ROMs, but bear in mind again the point above. Past that, again there's very little you can do apart from swapping the C board only. I'm not aware of any list of ones that will work in others, aside from specific mentions in the Dead Battery Society. Edit: I'd check the code ROM first - sadly you'll need a fairly decent reader to read that one. If you follow the jumper settings on an older game with normal EPROMs in it, you can rejumper the board to use the split images instead. That's the 4 pairs of zero ohm resistors and associated sockets near the C board.

As for a CPS1 with no sound - you've got a much better chance of getting it working. Check the volume control first, and the large capacitors. Broken legs of being missing entirely will basically turn the sound off due to no 12v. If the amp is functioning at all, usually you can get some random hums out of it by running your fingers along the amp pins. Past there it's time to check the op-amp (hard without an oscilloscope), and basic checks like the sound CPU clock signal - could be as simple as a dead crystal after all.

iatneH · Post by **iatneH** » Thu Jun 29, 2006 1:51 am

Thanks a lot for the tips, bloodflowers.

I'll take a closer look tomorrow maybe. Also might see if I can strike a deal with a sound-less motherboard too. That's to do in a week or two though.

footix · Post by **footix** » Thu Jun 29, 2006 8:32 am

no sound on a working game is usually a dead audio amplifier or a dead Z80

Post by **system11** » Thu Jun 29, 2006 10:56 am

footix wrote:no sound on a working game is usually a dead audio amplifier or a dead Z80

Um, both are uncommon failures to be quite honest. The #1 cause of dead sound is caps, usually through careless handling. Here's my repair log, see how many sound issues were caps compared to power amps.

footix · Post by **footix** » Thu Jun 29, 2006 11:27 am

i did get two mobos that showed sound failures, one had the Z80 toasted and the other had some amplifier failure

Stefan_L · Post by **Stefan_L** » Thu Jun 29, 2006 8:56 pm

bloodflowers wrote:All CPS1 boards are not created equal. Some of them actually have more ram than others... Also, there are a couple of PALs that may vary between game or board revision - never worked out which matters to which, but I did find that Carrier Airwing would run on some boards and not others

So there is CPS1 mainboards that are totally incompatible with certain games?
The only game i know is "Lost World" that shows minor graphics glitch on any other than it's (forgot number) mainboard.