Capcom cps1 problems

[astrodan88]

I'm hoping someone here has some experience with cps1 and can offer some advice.

I just bought a lot of several cps1 boards, many of which were non-working or had problems. I've tested them out and swapped out a and b boards with known working boards to try and isolate problems. After pairing up the working stuffs, I'm still at a loss on the rest. Here it goes:

First:
Does anyone know of if there is any info out there about which cps1 games have interchangable A boards? I know most can be swapped, but not all, IIRC. Can any one shed any light or confirm?

Second:
I have a Mercs board and I get no picture. I originally got no sound but after repairing a visibly broken trace on the A board I get one of the BGM selections endlessly looping but still no picture.
Mercs uses an A board that is visibly different than most (it's longer and has a slightly different component configuration; I'm not sure what, if any, are the tech differences). I swapped the B board with a known working A from a Magic Sword (which is the shorter type A) and got no sound or picture. I swapped with an A from Area 88 (which is the same length as Mercs but still has a slightly different layout) and got the same results are the original A: no picture, looping BMG track.

I have visually inspected the board and resocketed the chips; still the same. I'm guessing there's some problem with the B board but I'm at a loss.

Third: an easy one (I think):
Knights of the Round: It powers on with sound but with severe graphic problems (most of screen black; some partial sprites). I know the A board works (swapped with a magic sword B and was 100%) so I think it is a simple suicide battery issue.

I understand that when they suicide the graphics go with it, so I'm guessing that's it but I've never seen a suicide dead board powered. Can anyone confirm what a board with a dead battery would be showing?

Lastly:
I have a magic sword that shows no picture or sound. I swapped the A with another working magic sword B and got picture and sound but graphic glitches (images were doubled horizontally). When I put the the B board on a working A I still got nothing.
So, the A board works partially but there's clearly something wrong with the B board as it's giving nothing. A visual inspection and resocket yeilds no positive results.


I know that's quite a laundry list of pcb woes. My apologies. Any input would be appreciated.
Thanks!

 

[channelmaniac]

OK...

When a CPS 1 boardset plays music but does nothing else when turned on then the 68000 CPU and the program section of the board is dead. The Z80 and sound section is working.

Check the program ROMs for bad ROMs, bent pins, and incorrectly set jumpers for ROM types. Next check for broken traces and bad connections between the A and B boards. Next check the C board. If the C board is bad you'll get the same thing.

On the ones with graphic glitches, check for bad connections between the B and C boards. Also push down on the chip on the C board while it's powering up and see if the glitches improve. The C board chip may need to be resoldered.

For dead A boards, check for broken traces and shorting pins on the bottom. They left those RAM chip legs pretty long and if they bend and touch another leg then the board will do screwy things.

There's NO good way to check those RAM chips for bad ones. It'd be nice if someone wrote a test routine. The one from Capcom on the board doesn't work for shit.

RJ

 

[68k]

Without the 68000, nothing would function. I have halted the 68000 on a CPS1 board and everything including the sound stops. I'm suspecting a video-related issue here, possibly a cold solder joint somewhere. It is not a dead 68000.

 

[Xian Xi]

On CPS1 boards check those black/blue jumpers on the outside edges, sometimes they are broken off. I had a Final Fight that had one broken and would just keep resetting. Those jumpers connect some pins from A to B.

 

[scgon]

Third: an easy one (I think):
Knights of the Round: It powers on with sound but with severe graphic problems (most of screen black; some partial sprites). I know the A board works (swapped with a magic sword B and was 100%) so I think it is a simple suicide battery issue.


--> I have two Knights of the Round with the same issue, getting them brought back to life as I assumed they suicided, seemed to fit the profile anyway. Should know early next week when I'm done with the repair.

 

[channelmaniac]

Without the 68000, nothing would function. I have halted the 68000 on a CPS1 board and everything including the sound stops. I'm suspecting a video-related issue here, possibly a cold solder joint somewhere. It is not a dead 68000.

How did you "halt" the CPU?

I based my diagnosis on the fact that the sound subsystem was working and there were NO address or data lines pulsing on the program ROMs on the B board. The 68000 CPU was not even trying to read them.

 

[68k]

When pin 19 on the 68000 (PLCC package as used on the CPS1) is grounded, the CPU is halted, and is basically disabled. You can actually adjust the clock speed of the CPU while it is halted. Once you remove the ground, the CPU resumes. This will force some hardware to reboot. The pinout is different for DIP and ceramic PGAs.

While halted, the audio subsystem (Z80, YM2151) does not function.

 

[channelmaniac]

You should check to see if the HALT* pin on the Z80 is hooked to that one on the 68000 CPU as well.

 

[68k]

They aren't connected to anything. I don't know exactly what function it serves in most applications, but I have never seen a trace tied to it, and most of these boards aren't multi-layered.

You can halt the Z80, and in most cases, the game will not freeze. The synth will cease to function, of course. Doing any of this to a Neo causes it to reboot, no surprise there.

 

[dark penguin]

As far as compatibility between boards goes, I use this handy chart:

http://www.arcadecollecting.com/info/cps-b_numbers.html

If you scroll down to the bottom they have a couple lines explaining C board swapping and the chart itself shows which games carry which board revision.