Pac Man plus just shows random horizontal colored lines

Vectorman

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Pac Man plus just shows random horizontal colored lines

Guys,

Another weird problem just came up. I've got a Pac Man plus that was working perfectly with new monitor until moments ago. Now it alternates between no picture at all, and a dozen or so colored horizontal lines of various thicknesses from the top of the screen to the bottom.

This is NOT a monitor problem - the picture is perfect and stable. The lines are coming from the boards. tried re-seating the chips - same outcome but lines are in different places and colors.

Where should I look for this problem on the board?

Thanks for any direction you can give me,
John
 

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1) are all your fuses good?

2) does flexing the edge connector make it work?

3) can you post a pic of the lines?
 
1) are all your fuses good?

2) does flexing the edge connector make it work?

3) can you post a pic of the lines?

1) yes
2) no
3) no, but I'll see if I can find a way. I forgot to bring a means to get pics from my camera (or phone) to my computer.

Thanks,
John
 
Howdy..

Kinda hard to diagnose it with that little information, but I'll give it a shot. Horizontal timing ( 3R, 3S, 2P and 8C ) seems to be okay as the picture appears to be stable horizontally. Vertical timing (2R, 2S, 2P and 5M ) looks somewhat suspect as the same pattern is repeated all the way down, although this could also be due to (many) other things.

I'd start with checking the vsync and vertical counters and take it from there..

-Yvo
 
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