Missing transparencies in sprites

barakka

Twinkle Star Sprite
Joined
Mar 17, 2005
Posts
32
Hello,
I have an MV1A with an unusual graphical problem, please see the attached photo:

NEOGEO Sprites.jpg

Basically it looks like the machine is missing the transparency features and all the sprites overlap.

Does someone have an idea of what could be the problem?
Maybe a dead custom chip? Which chip does the mixing of sprites?
 

konrad

NEST Puppet
Joined
Aug 20, 2013
Posts
163
Hello,
I have an MV1A with an unusual graphical problem, please see the attached photo:

View attachment 59046

Basically it looks like the machine is missing the transparency features and all the sprites overlap.

Does someone have an idea of what could be the problem?
Maybe a dead custom chip? Which chip does the mixing of sprites?

Clean the contacts with alcohol and the slot and when you insert the cartridge sometimes you don't have to put it in until the end, leave it inside more or less halfway.
 

ChuChu Flamingo

We have purposely, trained him wrong, ...as a joke
Joined
Nov 23, 2010
Posts
2,306
What konrad said.

But also pull the cartridge connector out and reinsert it (the black, white, black connector pictured below is what it looks like without the cartridge pins). Sometimes it can come undone. I thought my MV1f needed repair but it was just the cartridge connector being pushed up.

https://wiki.neogeodev.org/index.php?title=MV1A
 

barakka

Twinkle Star Sprite
Joined
Mar 17, 2005
Posts
32
Unfortunately it's not something that relates to dirty contacts, this board has an history of multiple failures.
Anyway, after some repairs was working Ok, but then it had:

Z80 error (still does it sometimes)
Watchdog (probably caused by the next problem)
Work ram error (replaced both chips)
Crosshatch of death (Bridged GA11 Neo-Buf).

After fixing those, came the missing transparency problem.

Could someone explain what chip does the mixing (transparency/priority)?
I think the NEO-ZMC2 has been replaced sometime ago, but maybe it has developed a fault?
 

barakka

Twinkle Star Sprite
Joined
Mar 17, 2005
Posts
32
Solved, it was the NEO-ZMC2.
I've noticed that pin 4 [DOTA] was stuck high, which according to the neogeodev wiki meant:
DOTA: High when pixel A is opaque (color > 0)
Replacing the chip fixed the problem.
 

barakka

Twinkle Star Sprite
Joined
Mar 17, 2005
Posts
32
And just a few hours later is dead again...

I get a red screen with fast reset in the diag bios.
 
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