r/neogeo • u/jtoney7852 • 3d ago

Discussion MVS 1 slot issues - not working.

Gallery image

Gallery image

Original style mvs 1 slot. This thing is starting to make me pull out my hair. It's stuck in the cross patch pattern. Now allow me to explain what's going on with it. I bought this unknowing what the condition was. I also bought a cartridge for real cheap and found that the cartridge didn't work. I have since replaced the battery since it was leaking, and replaced the crystal that was adjacent to it.

Recently I also purchased another one slot motherboard but the smaller version. It is working fully and all the cartridges that came with it are working as well.

So I tried the new cartridges in that old motherboard and they don't read period all I get is that cross patch Period however if I put that old cartridge in that's not working I can get Garbage on my screen Period so now I'm pulling out my hair because I don't know what's causing any of this and I'm not sure what is responsible for reading the cartridge. I've looked inside the cartridge slots and I don't see any Grime inside of the connector or anything that was suggest corrosion or damage.

So can anyone tell me what chip is responsible for reading the cartridge on that old motherboard and what I can start looking at and checking? I'm unsure of how exactly to go about doing this. I know my voltage is good I know all that

8 Upvotes

100% Upvoted

15 comments sorted by

3

u/TooManyBulborbs 3d ago

Check for corrosion damage in the battery section

1

u/jtoney7852 3d ago

There's none

2

u/TooManyBulborbs 3d ago

The crosshatch screen means the MVS finished its self tests but the 68000 CPU couldn't find any bootable code in the P1 ROM chip in the game cartridge.

If you don't even get that and instead just garbage blocks and it flickers, then there's a core system problem between the 68000 CPU, the two work RAM chips (sometimes the backup rams too) and the System ROM (usually labeled SP-U1, 40 pin DIP chip)

Check for cuts or gouge damage under the board. Also corrosion.

2

u/maki9000 2d ago

that just means you are not able to spot it ;)

send good pics of the battery area and the PCB top & bottom

2

u/Neo-Alec AES 2d ago

Test traces with a multimeter. Sometimes they appear corroded but work fine, while other times they look fine but are actually broken.

2

u/jtoney7852 7h ago

https://imgur.com/a/IxCGVi3

Here are those photos

1

u/maki9000 7h ago

thanks for posting these

turns out I was wrong, the traces look fine

as TooManyBulborbs said, crosshatch means the P ROM isn't starting, traces need to be checked, could be anywhere between the slot and the actual ICs

there is also a test PCB for for DIAG bios for that: https://www.arcade-projects.com/threads/neogeo-diag-bios-crosshatch-testing-custom-prog-board.25130/

https://wiki.neogeodev.org/index.php?title=MVS_cartridge_pinout

1

u/jtoney7852 6h ago

Do you know which ICs handle that?

1

u/maki9000 6h ago

well those datalines will be multiplexed, depending on the model different ICs are involved, the 68k actually runs the program

here is a really good tip: https://www.neo-geo.com/forums/index.php?threads/mv2f-only-crosshatch.265141/

use a Unibios, then put in a cart, turn it on and use the memviewer, the interrupted datalines should be clearer then, can be calculated from the displayed value

at address 000100 is should show NEO-GEO, what does yours show?

2

u/jtoney7852 6h ago

Ill have to get one. Don't have unibios available to me at this time.

1

u/maki9000 5h ago

get a Unibios in any case, also get a DIAG Bios if you plan to fix more MVS (you might need it for this one as well)

EEPROM burners/erasers are cheap, but the EEPROM IC itself can be expensive by now, might not be worthwhile if you only need one or two BIOS ICs

there is also a QUAD bios PCB, but I can't find anyone selling that right now

1

u/jtoney7852 1h ago

Money is really tight right now so it's going to have to wait. I'm hoping for other suggestions that I can try in the meantime.

1

u/maki9000 5h ago

btw it should be the NE0-B1 IC you want to check for connections:
https://wiki.neogeodev.org/index.php?title=NEO-B1

all the "P" pins/traces

https://wiki.neogeodev.org/index.php?title=P_bus

edit:
actually for your chipset (first gen), its the B0:
https://wiki.neogeodev.org/index.php?title=PRO-B0

1

u/jtoney7852 3h ago

The B0 looks to just handle joystick input

1

u/jtoney7852 2d ago

I will endeavor to post some when I get home this afternoon.