Mvs1B1 graphic issue blue screen/watchdog -can’t use diag bios

Tengugurl

Cheng's Errand Boy
Joined
Feb 9, 2017
Posts
111
Hi!
Just sharing what I learned on my latest mvs fix tonight :)

TL;dr mvs is stuck on watch dog and unibios can’t be used, try what I did and you may have luck

1) started out with a parts console that had a lot of corrosion, cleaned the ICs with a fiberglass pen
2) tested with diag bios and no image just a garbled mess
3) thought to self maybe it’s video ram related.
4) replaced the crappy z80 ram patch job the previous owner did and added legit sockets to test out the z80 rams I have lying around
5) got it to boot to the unibios screen yay! But it was still illegible text
6) kept cleaning cleaning cleaning those pins on the bram and vram- lucked out and saw something that looked like vram as the error, sure enough it was and I saw it was the 32k ram upper here is a great link for those who may need it
7) sharing some knowledge on how to read the locations if you have such a jumbled mess and you can’t get enough text to say if it’s upper/lower


Here is a simple example:
ACTUAL: AAA9
EXPECTED: AAAA

AA in the actual are upper and A9 is the lower
It doesn’t match expected so prob is lower

Mine reads that it was an upper issue if we follow the same logic
8) replaced that bad boy upper ram issue and ….tada fixed!
9) ran it through the diag test a few times
10) popped in a test cart (yes you need a specific cart with specific diag m1 bios inside the car + the regular unibios—lesson learned there haha +++++ to one of my fav people on the forum. He knows how awesome he is for helping me level up my skills
11) popped in a cart with the unibios and I am off to the races

Hope this helps someone who runs into a similar issue :)

If you need help, I hope I can be a fraction as helpful as those who have been cheering me on! <3

Yay for fixing parts neo geo consoles.
 

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Last edited:

Tengugurl

Cheng's Errand Boy
Joined
Feb 9, 2017
Posts
111
I replaced the upper.

The example above was from the Link so I didn’t write it incorrectly as I get weird stage freight when I have to post “this is what I learned” posts lol
 

BIG BEAR

SHOCKbox Developer,
20 Year Member
Joined
Dec 14, 2001
Posts
8,230
Ok.I thought you were posting you actual results..my bad.
Congrats on the repair!
BB
 
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