Neo Geo MVS MV-1A Won't Go Beyond Garbage Screen

[riderigo]

I bought a junk MVS MV-1A in hopes of an easy repair, but when I turn it on, I get this bizarre screen. I've replaced all the capacitors, cut the 12V leg on that voltage regulator, replaced the smaller 32.768 crystal, and removed the battery.

Thank you.

 

[XianXi]

Did you probe the D4990?

 

[riderigo]

Yes. It registers 5V on the bottom legs according to the voltmeter. And there was no battery leakage. The board is more or less satisfactory clean. If a backup data error causes this wouldn't the screen be brighter and be more solid like your typical Neo Geo boot sequence?

And I installed the Neo Diagnostic Bios sp1 and it will not go pass this screen.

 

[ack]

If its a static image (watchdog not resetting the board) you might check the clock pin on the 68k.

Its pretty common for MV-1A boards to have issues because a high failure rate of the NEO-BUF ICs, which causes all kinds of problems.

https://wiki.neogeodev.org/index.php?title=NEO-BUF

Furrtek made a replacement NEO-BUF

https://github.com/neogeodev/NeoChips/tree/master/NEO-BUF
https://www.tindie.com/products/furrtek/neo-buf-replacement/

 

[riderigo]

Yeah, I'm going to have to order the Neo-Buf parts from a pcb fabricator as furrtek has none for sale. But considering what's going on in China, it will be quite a while before I finally fix this unit.