Ms Pac PCB Problem

troxel

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Donor 7 years: 2015-2021
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Working on the PCB on the bench, and the game looks like the sync is off and sometimes I can see sets of zeros. However, the game is playing blind. I know it's not the monitor, because I tested it in another and getting the same problem.

I removed the AUX card and replaced the Z80.

Any suggestions to start troubleshooting this?

Thanks again,
Theron
 

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I wish I could help with the problem, but I just wanted to comment and say I like the little PSOne LCD monitor. :) I was thinking of doing that for my bench setup too, but I have a supergun that I can use with a small TV instead.
 
SuperGunGuru--I have a computer power supply, Sega Genesis controller, along with a PS1 LCD for my test station. Works really well and it's compact. It all fits in a toolbox so I can take it on the go, too. It has helped me narrow down problems pretty quickly.

And now the Ms Pac-Man :) ...any thoughts on the problem(s)?

Theron
 
I would start by looking at the memory section. VRAM addresser, and the counters. 2114 sockets and the like. All zeros or F's on the screen is VRAM addresser, or bad RAm, but the breakup of these is most likely the counters below that on the board. Once all that gets fixed, you hope to get the the screen of garbage. The screen of garbage characters and fragments means now you move to getting the cpu to run!

Mike
 
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