CPS3

[John Bennett]

A (fair) while ago, I offered to look at this CPS3 for a VAC-er living around the corner from me (Hi Geldra

).

It was an 'unknown' motherboard with some missing input filters and suspicious burnt bits.

Anyway, with enough extra parts obtained (by Geldra) it started up, suprisingly!

A missing CD ROM error came up, even with known working drives.

Fortunately via a cheap (irreparably wrecked - massive PPU torn off) donor board, the missing filters were replaced (and an audio cap).

Unsuprisingly they didn't fix the CDrom issue.

So I swapped over the SCSI controller (also available fairly cheaply as it's off-the-shelf).

And it started up!

When copying onto the flash SIMM, it failed.

Looking at one of the SIMMs, the reason why was clear (top one in photo). A chip had actually fallen off.

So a 32MB SIMM was obtained (bottom SIMM) and the chip nicked off it (note they're in 'handed' pairs, so you need the correct side, I presume).

And into the game it went.

And almost there, but player 2 couldn't move down

.

So I probed around the input filters. And via a multimeter I discovered the IOU custom was damaged!

That maybe explained why the board had missing filters - someone had tried to fix it and given up.

So I swapped over the IOU (took longer than it should, but I'm not so experienced in 200+ pin TQFP swapping).

Success!

And one thing less cluttering up my office

.

 

[yoganuggy]

great job, especially on that QFP stuff. I love the way you casually describe using just a multimeter to discover an IOU custom was damaged. That would be impossible for 99% of folk

 

[John Bennett]

Thanks

. It's a neat trick for the multimeter to do a basic output test of logic ICs that I read on a forum years ago.
Switch the game off.

Set it to the diode setting and put the red probe on 0V/ground.

Now put the black probe on a series of pins that should be doing the same thing. If one of them gives a radically different reading then it's suspect.

I'd traced a few I/O pins back to that custom and the one for P2 down had a very different reading (0.2V vs 0.7V diode drop). So it was more of a confirmation, really.

Can also put the black probe onto 5V and red probe onto each pin to be thorough.

 

[geldra]

Absolute dark art genius level skills. Absolutely buzzing that John got this up and running.

 

[John Bennett]

Too kind! It was relatively a straightforward diagnosis compared to something that just blank screens.

 

[neo-geo-mvs]

Skillz

Nice one

 

[Flinnster]

Yeah awesome stuff

 

[Hawkeye]

Well done John! and a valuable asset to the community here you are.. Impressive work.

 

[extant83]

I take my hat off, great Job

 

[ShootTheCore]

Great repair! Make sure to open the white plastic capsule and replace the lithium battery in there if your board has one. This is the surprise I encountered on my CPS3 board when I opened the capsule:

 

[John Bennett]

Wow. The capsule is only present on the dead donor board, but I didn’t think to open it. What is the suicide battery actually doing?