Picked up a NeoGeo MVS with 'Backup Memory' error on boot. It was a solid fault returning a read/write mismatch on the same address every time - 0x00D00010 0xB255 and this is the first address in the backup memory region.
First step was to replace the rechargeable battery and inspect for and damage caused by battery leakage. In this case no damage was found so the root cause of the backup memory error elsewhere.
Probing around indicated a defective 74HC32 which is part of the decoding logic for the backup memory.
Decided to use Chipquik to remove the device rather than hot air - Chipquik is a low melting point alloy that says molten for several seconds allowing you to remove smd devices easily.
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| New battery and holder fitted |
The original 74HC32 came off the board easily and no damage to the PCB as the temperature required to remove it was low.
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| Original chip removed and pads cleaned |
The replacement part was slightly narrower that the original package size but fitted ok. Board booted up perfectly afterwards with no more memory errors.
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