Gorf Sprite/Text Issues

tomoro

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I've been having some issues with a Gorf cab we just got in, specifically intermittently, the sprites (especially the text) are vertically staggered across the screen, so one part of a letter will be where it should be, and the other part will be way down the screen. Typically when it works it boots messed up, fixes itself after about 30 minutes, then it works completely fine for another 30 minutes, then errors again.

Pins have all been reseated and cleaned on ICs and edge connectors, and cold solder joints have been searched out thoroughly. Voltage is right on expectations. Boards have also all been moved to different slots with no change in behavior, ruling out the comm board.

My current guess is something on the pattern board and not either ram board.

If anyone has any clues, even just where sprite generation/placement is located that might lead to this, I'd much appreciate it!
 

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looks like pattern board. if I had the test card gimmick for those I would fix them. but alas I do not

@KPW66 is my Astrocade sage, maybe he can help
 
I've been having some issues with a Gorf cab we just got in, specifically intermittently, the sprites (especially the text) are vertically staggered across the screen, so one part of a letter will be where it should be, and the other part will be way down the screen. Typically when it works it boots messed up, fixes itself after about 30 minutes, then it works completely fine for another 30 minutes, then errors again.

Pins have all been reseated and cleaned on ICs and edge connectors, and cold solder joints have been searched out thoroughly. Voltage is right on expectations. Boards have also all been moved to different slots with no change in behavior, ruling out the comm board.

My current guess is something on the pattern board and not either ram board.

If anyone has any clues, even just where sprite generation/placement is located that might lead to this, I'd much appreciate it!

Is the small text drawn wrong initially or does it only tear when the scrolling starts?
 
I too would think pattern board but would not rule out CPU board customs. Wouldn't be hard to diagnose which of those two on a bench
 
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