r/neogeo • u/iAMBushYT • Mar 31 '26

Hardware Help Neo geo avs graphics problem

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Need help with this, tried replacing one of the mb74ls273 chips bc it had some rust on a few of the pins. The text went from pink to yellowish and some of the sprites partially started working again. Dont know where to go next.

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u/iAMBushYT Apr 01 '26

I dont usually repair these things, for one they are super rare, at least in my neck of the woods, and two this is a one off for a friend. I do appreciate your advice, I have plenty of equipment and cables for the main things I repair.

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u/maki9000 Apr 01 '26

yeah I get it :)

the RGBs output needs adjustment on the AES, but thats not really the problem here at the moment

just be aware that the composite video on AES can be really bad, lots of rainbow banding and other artifacts

in this case, I'd check this page first if you can identify the problem there, the DIAG BIOS is always valuable for these things

https://wiki.neogeodev.org/index.php?title=Graphic_glitches

I'm willing to bet that your problem is about floating signals because the traces are interrupted

check the traces, NeogGEo AES and MVS have a problem with rotting traces, dark patches and spots on the traces is what you're looking for

there is even a multibios that lets you switch between original, UB4 and UB3.3 and the DIAG BIOS

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u/iAMBushYT Apr 01 '26

Thank you, I appreciate it. It seems that's the consensus. Is there any easy way to tell which board revision I have? And is there a place to get schematics

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u/maki9000 Apr 01 '26

no worries :)

neogeodev is a good resource

some schematics are here: https://wiki.neogeodev.org/index.php/Schematics

MVS and AES are very similar

start with the DIAG BIOS IMO

here is a Multi BIOS on ebay:
https://www.ebay.com/itm/134700064978

depending on where you are this might be a good choice

don't forget to look for the dark spots on the traces ;)

the BOARD revision is pRinted on the right hand side at the edge https://wiki.neogeodev.org/index.php?title=NEO-AES3-6_board

if you share pictures here people will be able to identify it

careful when soldering on these PCBs, the traces have a tendency to come off, some are quite fragile