MV2-01 ZMC2 repair - no C-Rom sprites?

avramce

Kabuki Klasher
Joined
Sep 24, 2019
Posts
125
I got a 2-slot board with heavy corrosion damage around the battery circuit:
https://www.mvs-scans.com/images/5/5d/Mv2-01_set1_top.jpg

At this point, I probed all the C-lines on the ZMC2 chip, restored all the connections between the C0 and the LSPC-A0, but I'm getting gameplay with sound and no characters on screen:

For LSPC-A0, restored connections for EVEN, H and LOAD


For PRO-C0, restored connections for GAD0 and GAD1

Whats weird is the static sprites on the screen are loading fine, but anything that I would assume comes from the C-Roms is not displaying on screen. I ran NeoDiag on the board, and supposedly, all tests passed.
 

ack

Ninja Combat Warrior
15 Year Member
Joined
Apr 9, 2009
Posts
538
The flow of sprite data on the zmc2 should be C0-31 as inputs and GAD0-3/DBD0-3 as outputs. In general you should expect to see pulsing on all of those pins.

I would verify connectivity between the zmc2 and the 2x neo-257 chips to the right of it and then from the neo-257 to the slots. The static images come from the S rom.

If the corrosion got to the zmc2 chip, its possible the chip is bad.
 

avramce

Kabuki Klasher
Joined
Sep 24, 2019
Posts
125
Thanks Ack, I pulled a ZMC2 from a donor board and have an image with tons of lines. Sounds like I have a stuck C-rom line, but I get pulses for all my inputs to the ZMC2, any suggestions on what to look at next?https://imgur.com/a/mxv7Uvu
 

ack

Ninja Combat Warrior
15 Year Member
Joined
Apr 9, 2009
Posts
538
I would verify connectivity between GAD/GBD lines from zmc2 to PRO-C0
 
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