Neo Geo MVS 2 Slot MOBO - Ram Error

9914ken

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Hey all, Ive had this motherboard for some time. Does anyone know of someone who can fix this? Or is this something that I can perhaps do on my own? Any help would be appreciated.

Ken N.
 

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Looks like one of the battery backup ram chips or interface circuitry to it are faulty. They are 8 bit chips so it looks like the high byte one. There are different 2 slot models, so can't tell you the chip locations off hand. If you have a scope or probe you could locate the battery backup chips and probe the data lines on them to see what is working or not as a starting point to troubleshoot the fault.
 
On my NEO-MVH MV2 (with stamp MVS V5 U) it is the 2 x 43256 SRAM chips (Sony CXK58256MM-12L) at 3H and 4H, just above the SP1 ROM.

A quick bit of continuity testing showed these are connected to the same address and data bus lines as the SP1 ROM. So, according to the pinouts for both, at a guess I would say 3H is this high byte. It could also be a WE, OE going to the RAM that is faulty as those are driven separately for 68000 addressing them as a word, hi byte or low byte.

If you have a different pcb version they may be elsewhere and/or different chip types.
 
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