CPS1 Repair Help

[twistedsymphony]

I recently picked up an original non-working Forgotten Worlds board set. This had some repair work done previously but looks to have had some additional issues come up.
It's a game I've really wanted as an original board set and it's a numbers matching A and B board set so I'm interested in getting this repaired so I can play and enjoy it.

This is what the board looks like:

outside of the program ROM stacking "repair" it's actually pretty clean with no signs of damage or other hacks.
it seems like the QFP44 Program ROM may have died and the did what you see here to fix it.
I have a few different ideas as to how to repair this proper, or at least more cleanly, but I don't think this repair is actually the problem.
The game boots and actually passes the ROM check which to me implies that this repair is actually good and working.

The problem is the graphics are messed up, and once it gets to gameplay it it freezes.

View: https://youtube.com/shorts/b6I2Uizgt3c?feature=share


So first and easiest check I swapped A-Boards with a known good working game. The A-Board seems to work fine except for sound. there is 0 sound out of this A-Board. and the graphical issues were exactly the same on the good working A-Board, also sound did work fine on the good A-Board, so we know that the graphical/gameplay issues are specific to the B-Board and the no sound issue is specific to the A-Board.

The few original ROMs on the board I was able to dump and confirm good. I did try flexing the board, putting pressure on the SMD chips none of that had any real effect.
Weirdly though I after swapping the A-Board and then swapping back it played perfectly fine! some graphics still had issues but gameplay was perfect.

View: https://youtu.be/D132HUoTwL0


Booting again after that it was busted again like the first video.

This gives me hope that the primary issue is just a bad connection somewhere, but my fear is that this is likely related to the CPS-B-01 chip. I know that the B-01 is often cross compatible with the B-21 and B-11 C-Boards, but I'm curious if the chips themselves are cross compatible.
Anyone with CPS1 repair experience I'd be interested in any advice on where to focus repair efforts given the errors.

 

[GoldenGlover]

I’d try reflowing that B-01 chip to see if it eliminates your graphic errors before diving down the CPS1 repair rabbit hole. The fact you said your B board briefly worked better when using another A gives me loose trace vibes.

 

[twistedsymphony]

The fact you said your B board briefly worked better when using another A gives me loose trace vibes.

It worked the same on a different A-Board, then worked better after putting it back on the original A-Board.
but yes I agree... lose trace vibes.

 

[twistedsymphony]

so my soldering iron has been refusing to work a lot recently, I decided to see if I could do a reflow and sure enough it didn't want to work. thinking about what else I could do I decided to program a new LWCHR PAL ... and sure enough that fixed the major issue the board was having! I've rebooted about a half dozen times and let it run for a while and it plays reliably now.

Still 2 issues left.
1. no audio on A-Board
2. still some graphics issues, certain sprites have jail bars.

playing around in MAME and intentionally corrupting graphics ROMs it's hard to narrow down since it has 64 bit graphics but it seems the graphics problem is related to the ROMs that make up the first half of the ROM region. I think this can rule out a CPS-B-01 issue, which is great, but it's likely one of the QFP44 chips that's a problem...

I'm open to suggestions on the no audio. I think it may be amplifier related as I don't even hear any buzzing when I turn the volume all the way up, nor when I touch the pins of the amp.

Interestingly it looks like someone's reflowed or replaced the amp and another part once before based on some flux on the PCB

 

[twistedsymphony]

So the new WCHR PAL seems to be holding, I haven't had any crashes or garbage on screen since the replacement even after multiple reboots.

Some graphics issues remain though. though playing with MAME and manually corrupting each graphics ROM and seeing which broken graphics match my game I've narrowed it down to one of the QFP44 ROMs along the top ROW, but given these are 64-bit graphics and it uses the whole row together for each asset I'm having some trouble narrowing it down further.

Any CPS1 graphics experts out there know of a good way I can definitively determine which ROM is bad without having to desolder and dump all 4 of them?