Miss Pac Issue, Two Seperate Boards, Same Problem, confirmed over two Hardware Sets.

Joshmans

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Miss Pac Issue, Two Seperate Boards, Same Problem, confirmed over two Hardware Sets.

The issue is a static screen of characters. This is on two of the boards now, so I suspect either I somehow zapped it (unlikely due to use of antistatic bags and grounded discharges, aswell as edge handling) or that it has something to do with the socketed chips.

Heres what I get on the screen. Both machines are running original Power-Supply at a solid and acceptable voltage and have working edge connectors.

The two pictures are from two seperate boards on two seperate sets of hardware.

http://imgur.com/a/p44lG

A hum from the amplification circuit can be heard, but thats about it.

Thanks for all the help so far, guys.
 
Does the screen change any or is it just stuck like that? First make sure dip #8 is off. After that I would check program roms, ram and cpu.
 
Thats a good sign. Usually if its a bad ram or rom it will watchdog and the garbage on the screen will change every reset.
 
Finally fixed the problem.

The issue was the Z80 Sync Bus having problems either via the pins on one board, or from a zip tie over trace fix wires on one.
 
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