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TheBurgerKing

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I have a CPS1 A board that has a minor graphical issue. B+C boards have been tested on two different A boards and work fine. The shadows and feet of the characters in SF2:CE, have a few vertical lines. Other than that, everything else is perfect. I did some probing on the board and compared it to the other working A boards. I havent found anything that stands out. Attached are a few pics of the artifacts. Any help or guidance would be greatly appreciated.


IMG_5044.jpeg
IMG_5047.jpeg
 
No such thing as "minor graphical issues" when it comes to CPS1 my man.
Often times if its A-board related/isolated its a dead or failing custom.
 
A dying graphics custom…

Or if you're lucky, check the pins on the connectors. Maybe a cold joint or two pins bridged on the solder side.

Check the chips on the A board that are socketed. Also the sockets themselves can corrode.
 
Thanks for the tips. Hopefully the CPS-A-01 isnt failing. These A boards are difficult to troubleshoot since a majority of the board is covered by the B board. I suspect this is a memory issue. Just a guess.
 
https://www.arcaniac.com/products/capcom-cps1-a-board-diagnostic-helper-repair-tool

If it were my board I’d try to simulate the error in mame to narrow it down first though. This one ended up being rom but you can at least see where the data is coming from and trace it from there into video memory (and see what kind of corruption can cause that kind of issue… stuck high or low line, what part of the addressing it might involve…)

https://www.arcade-projects.com/threads/lucky-moron-pcb-repair-4-killing-blade-pgm-cart.13939/
 
https://www.arcaniac.com/products/capcom-cps1-a-board-diagnostic-helper-repair-tool

If it were my board I’d try to simulate the error in mame to narrow it down first though. This one ended up being rom but you can at least see where the data is coming from and trace it from there into video memory (and see what kind of corruption can cause that kind of issue… stuck high or low line, what part of the addressing it might involve…)

https://www.arcade-projects.com/threads/lucky-moron-pcb-repair-4-killing-blade-pgm-cart.13939/
Using MAME to simulate the error, great idea. Thank you for the suggestion. As for the helper tool, definitely pricey. Especially if I only use it for this one board.
 
I have a WW board with the accelerator hack that is doing this but probably 75% bigger jail bar sprites on only the characters.
 
You may or may not be aware that you can steal a A-01 custom to fix a CPS1 from a CPS2 A-board.
Up until very recently this was an affordable repair/solution.
 
You may or may not be aware that you can steal a A-01 custom to fix a CPS1 from a CPS2 A-board.
Up until very recently this was an affordable repair/solution.
Yup. I read the chips are more reliable due to manufacturing changes. Don't know how true that is. I would think if the the A-01 chip was bad, the graphical issues would be much worse. What I am experiencing is so minor. Then again, these boards are unpredictable.
 
Using MAME to simulate the error, great idea. Thank you for the suggestion. As for the helper tool, definitely pricey. Especially if I only use it for this one board.

If you have the diagnostic ability and tools to work on this, I can lend you a set of those helpers. Cps1 A boards do have public schematics which is nice, but pcb repair is tough in the first place and most A board errors do dead-end at the custom.
 
If you have the diagnostic ability and tools to work on this, I can lend you a set of those helpers. Cps1 A boards do have public schematics which is nice, but pcb repair is tough in the first place and most A board errors do dead-end at the custom.
Thank you for the offer. Since this is just one board, I will grind it out. Now if I decide to fix a few others, I will definitely take you up on that offer. I have a Rigol o-scope, logic probe, etc. Fixing old game systems is actually hobby of mine They are way more straight forward. These CPS1 boards have a lot of moving parts. Definitely a longer troubleshooting process. BTW the board is a 89626A-4. I can't believe I didn't put that in my original post.
 
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Yea, such a pitta that custom.
Don't trash these dead A-boards however, some day we might get a FPGA replacement solution.
Never give up hope! :saint:
As popular as this hobby is and all the MiSTer progress, I am shocked there isn't one already.
 
If you try the mame route, dip3 bank C is a pause function that might help you when you’re messing with memory
 
Well its not the CPS-A-01. I swapped that out tonight. Same issue. Also swapped out some of the LS245s. On a side note, I did fix another A board and C board. The C Board was tricky. It would randomly cause color issues on boot. If you reset the board a few time, it would display correctly. It was a flaky PAL - IOC1. I was able to download the .jed (Thank you Porchy and Caius) and burn it onto a GAL16V8. Things are much easier to troubleshoot when you have multiple boards to test with. Anyway, back to this issue.
 
i'm amazed there arent replacement chips yet, given the number of dofferent bootlegs that got around it using everything from shitloads of ttl to old pld's
 
This has been repaired. Bad RAM at location 2L. Replaced the RAM chip and the graphical glitches are gone. Lots of troubleshooting with this one. When troubleshooting these boards, especially ram issues, I highly recommend getting female pin headers and socketing the ZIP ram. I cut the strips into rows of 14 pins, straightened the legs on the ZIP chips and inserted them. It made RAM testing much easier. I could easily swap in a known good chip and move on.
 
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