4 Slot missing graphics

RetroTechRewind

Crazed MVS Addict
Hello all.

Wanted some possible insight with a problem i'm having.

Bought a 4 slot on ebay that was listed as untested, so I assumed it was broken...and I was right.

It had bad caps (replaced all of them), and a work ram error shown below.

IMAG2142.jpg

Since it was the second set of bits, replaced the ram at G9 and it fixed the error.

It also had battery leakage, which I believe I fixed. I tested continuity between the traces shown below, and only the first 4 were bad. The rest look okay, but I'm thinking I'll check all of them regardless again now.


IMAG2144.jpg


Anyway, when I power it on, it recognizes games perfectly fine. Audio works etc. I tried MS2, however, the health bars and credit displays on the bottom are missing. There's only the credit display for player 2, but no health bar.

(pic coming later when I get home from work)

I"m assuming it has something to do with the connections to S1 on the cart. It does this on every game I put in. I've cleared the backup ram as well. Again, I'll post pics of the actual scree later. Everything else works fine. Sound, controls, etc.

I have replacement chips for the top board if need be.

Would love to hear some input, thanks for any help friends!
 

darknezz19

Neo Bubble Buster
I guess burning the diagnostic rom and seeing what it throws is out of the question?

Don't really know enough to diagnose stuff like this based on just symptoms, but sure want to learn.
 

RetroTechRewind

Crazed MVS Addict
I guess burning the diagnostic rom and seeing what it throws is out of the question?

Don't really know enough to diagnose stuff like this based on just symptoms, but sure want to learn.

I have one burned and tried it. Says all tests passed, so that just adds more confusion to the mix.


Depending on certain symptoms, you'll figure out the general problem area. There's lots of info out there. Check out the Neo Geo Development Wiki.
 

shadowkn55

Jaguar Ninja
The diagnostic bios doesn't have access to pixel data so you'll have to manually check the s-rom connections.
 

mikejmoffitt

Mickey's Coach
Maybe check the /CE line going to the S ROM on the cart. Looks like the FIX layer works with the internal S ROM (otherwise the Work RAM error wouldn't show) but perhaps there is no data from the cartridge. If it's missing entirely, and not just vertical lines (data line issues) or wrong tiles (addressing issues), it might not be outputting. That said, I believe open bus behavior for the S ROM bus generally floats to a '1' instead of '0' so your mileage may vary.
 
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