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GumGum

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My mv1fs chucked out error "hardware test failed backup ram". Do you guys know which backup ram that i need to replace based on the screenshot? is it lower or higher backup ram that needs replacement? thanks
F9826887-A9BB-4459-87FA-B8322B8F14DF.jpeg
 
i see. I replaced the original with coin cell battery holder like few weeks ago. Everything seems to run fine up until now.
Do you reckon it has anything to do with coin cell battery holder installed? or was it more a very common issue with backup ram failure in mv1fs?
 
i see. I replaced the original with coin cell battery holder like few weeks ago. Everything seems to run fine up until now.
Do you reckon it has anything to do with coin cell battery holder installed? or was it more a very common issue with backup ram failure in mv1fs?

No, the coin cell battery should be fine (but unless you disabled the recharging circuit make sure you're using a rechargeable LIR2032 and not a CR2032). What I was thinking was that the old battery might have leaked, and eaten through some of the traces in the area where the backup RAM is. Seems a little odd that both would fail in the same way. But, always possible. If you have the NeoDiagnostics BIOS that might give more details. But as I said, from my reading of the error both chips are showing the wrong value. If only the low ram had failed, I would expect to see 5540 and if it were just the high it would read B255.
 
ok oddest thing just happened. I took the board, and then clean up the solder side with isopropyl alcohol because I see some glue residue remaint... then when I hook up the board back, ram backup failure is gone.... it's odd...
 
ok oddest thing just happened. I took the board, and then clean up the solder side with isopropyl alcohol because I see some glue residue remaint... then when I hook up the board back, ram backup failure is gone.... it's odd...
A possible short? Maybe?
 
ok oddest thing just happened. I took the board, and then clean up the solder side with isopropyl alcohol because I see some glue residue remaint... then when I hook up the board back, ram backup failure is gone.... it's odd...
Could have been something conductive that was causing a short that you cleaned off. (Shrug)

I’d get the diagnostic bios and see if it finds any other issues, but working is working.
 
B240 is a very odd error that has to do with the transistors in the backup RAM section. The only time I've ever seen it I found one of the transistors had gone open. The battery crud creeped up the leg into the transistor. I shared my findings on this repair years ago on the Neo Geo forums and Nightmare Tony himself popped into my thread to comment. :)
 
The battery crud creeped up the leg into the transistor.
I did reseat the coin cell battery after cleaning up all the flux / adhesive residue.... so perhaps it's the coin cepp battery reseating that resolve the issue....?
 
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