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CPS1 flickering graphic layers + reboot

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xnz136

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My SFII CE board worked a few years ago. Pulled it out the other night, and it seems to have developed a fault. Several of the graphics layers flicker on and off (the characters and the sky BG in the intro, title logo, character portraits on the select screen) and the game reboots when trying to start a match, both during attract mode and when starting actual play.
A board is confirmed good.
5v is good.

Any thoughts if this sounds like a B-board or C-board fault? My first step was going to be reflowing the A board connectors on the B-board.
 
That's a good start. You can also check the program roms if you have an eprom programer. Then if all checks, your most probable candidate is the C Board.
 
Must be a corrossion, a cold solder or C Board gone south IMO.
 
Would there be any harm in swapping in a compatible C-board from a working game (or swapping the SFIICE C-board onto a confirmed working B-board)?
 
My Final Fight board experiences similar flickering in certain areas and certain background elements have begun to display only in yellow.

Keeping an eye on this thread to see if any of the suggestions work for you.
 

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Reflowing connectors made no change. Looks like I have a compatible C-board from a working game, will swap that in and see if it fixes the issue. If it does fix the problem, I'll reflow the CPS-B-21 chip, and if that doesn't work... guess I'll either need to source a replacement B-21 chip or just get a whole new C-board.
 
Be careful about "compatible" C Boards, even if it has a B-21 it could be either modded to work in default mode or it could just be from factory like that. Post a picture of your C Board, that might help clarifying things.
 
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The II' Turbo is the good one, II' is the bad one. I'd already gone ahead and swapped the C-boards, and Turbo's C-board made the CE board work properly. I tried swapping just the PAL chips into the faulty C-board and observed no change. Reflowed the CPS-B-21 chip and the LSs while I was at it on the bad one -- no change. The CE's PALs worked fine when used on the Turbo PCB.

I don't have a logic probe so I can't readily check any components. Guessing the CPS chip is the most likely failure point based on the symptoms, but are any other C-board components common failure points? Seems like UTSource no longer has loose CPS chips for sale, so I assume I'll have to buy a whole C-board (or a B+C, since those seem to show up more frequently than just loose Cs).
 
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Look at pins from 41 to 48 from the B21. Do they look the same? Connected to the same place on both pcbs?
 
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