Kaneko Super Nova hardware - A OK B-NG :(

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So I have a game that only booted sometimes, and now it doesn't boot at all. I've only got the one Super Nova cart so I can't test another cart to see if it's the motherboard or not.

If the motherboard is plugged in by itself should I get anything at all?



Managed to get the PCB to boot as far as the self-check. It says A - OK B -NG. Now if only I had any idea what A was and what B was. I'm assuming one of them is U8 and the other U10 but no idea which is which.

 

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Well, I've replaced both U8 and U10 to no avail.

Does anyone know what the startup checks are for on SuperNova? What it checks for A and what it checks for B? Maybe ROMs then RAM?

There are the 2 socketed program roms you'd swap out to change languages, two 20-pin socketed chips that aren't listed in the MAME rom (I'm assuming they're in the SuperNova BIOS file), and 6 surface mount chips on the cart.

I've tried hex editing each different file in the romset to have a bunch of garbage in various places in hopes of MAME failing one of the checks, but it just always says both A and B are okay. You can get some pretty rad graphic and sound issues that way though!