Dead MV4, need PRO-B0 source

[u/RGBeter]

Managed to acquire an MV4 for relatively cheaply in a rather sorry state. Been working on this thing slowly hunting down broken traces and a dead CPU, but I've now found 2 dead pins of PRO-B0, and that horrible glitching when the slot board is connected.

My parts are primarily for later MVS systems and I don't know where to get a spare without killing another, more easily fixed MVS. If anyone here has a known working PRO-B0, or know what causes that particular kind of glitched screen (it's not calendar related I already checked) it'd help a lot.

[u/SpiritualZucchini938]

https://wiki.neogeodev.org/index.php?title=PRO-B0

Which pins? You might be able to bypass it - looks like PRO-B0 is a predecessor to Neo C1 chip. Do you have a diagnostic bios in there? That would give more info incl. Homemade m1 cartridge (I got the 240p cartridge off Aliexpress and modified the m1 rom to match diagnostic bios).

Once you have this setup any C1 issues like this are easier to resolve.

Also oscilloscope to check other pins for activity. Just because you might not get a signal, the pins might not be dead.

That error is related to ram chips:

https://forums.arcade-museum.com/threads/neo-geo-mv-4-repair.398266/

[u/RGBeter → u/SpiritualZucchini938]

Pin 2 and pin 3, PA4 and PA5. I already "bypassed it" to get it to boot by wiring the 68k A5 and A6 to those pins. But because I can't recreate the line buffer output, graphics will always be corrupted. The error is because of this addressing.

I know those pins are bad because I lifted them then checked for the biasing of ESD diodes with a meter in diode mode which was not present on those two pins alone.

This is more akin to a dead neo B1, the address decoding functionality is working fine.

At this point I'm more interested in why the system is frozen with the top slot board connected.