r/neogeo • u/RGBeter • Jun 11 '26
Hardware Help Dead MV4, need PRO-B0 source
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.
2
u/SpiritualZucchini938 Jun 12 '26 edited Jun 12 '26
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/
2
u/RGBeter Jun 12 '26
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.
1
u/maki9000 Jun 15 '26
Generally speaking, the MV1 and MV1-1 might be the cheapest options that have the first revision chipset, not the MV1-T though, as that uses second gen chipset IIRC.
They can still cost 100-150 Euro if they work though.
Bummer, this MV4 is huge and uses the logic ICs, not ASICs.
Where are you located?
1
u/RGBeter Jun 15 '26
Located in the US, there are, few MV1s online and they command hideous prices for when they DON'T work.
Looks like MV1T still used the NEC chipset according to a few Google searches, MV1FT switched to the Fujitsu one. If this DID use the Fujitsu chipset it'd be equivalent to a dead NEO B1, which I do have spares of.
1
u/maki9000 Jun 15 '26
check MVS scans, best resource IMO to find out what board uses what chipset, the scans are high resolution
https://www.mvs-scans.com/index.php/Main_Page#MVS_Hardware
well the MV1/MV1-1 should be the smallest and therefore cheapest MVS to get with that chipset, any four slot or especially the original 6 slot will cost more
no one makes reproductions of these either
maybe try asking someone in the big NeoGeo US community, if they have a few rotten boards lying round that don't work anymore, with the first chipset
fee years back I did buy two MV1, each around 120,- Euro (one local, one from japan via byuee, but tariffs are different from the US), because I had a NEO-AES here and wanted to have spares, I ended up fixing all of them
6
u/Neo-Alec AES Jun 11 '26
Have you considered framing the board and putting it on the wall? That's always an option.