ms pac double/split characters

TheShanMan

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Was working fine one day and the next I start seeing this. Only happens on the left half of the screen. As you can see from the 2 ghosts and ms pac, they start out as cut in half (when right in the center of the screen), and then as they move left they just become 2 whole images, like the 3rd ghost.

Anyone know what causes this? I tried reseating the daughter boards and also took out the filter board.
 

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None of the ones on the mikesarcade page quite match what I'm seeing. I'd love to find the place that documents this problem. :)
 
Looking at the pic I would check out the character roms 5E & 5F.
Could be a bad 7489 ram. Im thinking the problem is down around F/H rows 1-3. I cant remember off the top of my head but I have seen that a couple times.
 
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Image99.jpg



Double characters
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2F p10,13 high

Directly from... http://www.arcadegameover.com/pactrouble.html
 
Yeah, just saw that one. That's certainly the closest match, but definitely not the same. Again, this only happens for sprites on the left half of the screen, and the 2nd image is to the left of the real image, not the right. Still think it's the same problem?

I've reseated the vram board a few times (as mentioned).
 
Looking at the pic I would check out the character roms 5E & 5F.
Could be a bad 7489 ram. Im thinking the problem is down around F/H rows 1-3. I cant remember off the top of my head but I have seen that a couple times.

Am I wrong in thinking it wouldn't be the roms since the sprites look fine on the right side of the screen but split/double on the left half? I've wondered about the ram from the beginning, but I don't claim to be an expert. :)

Assuming they are socketed, I'll try swapping some rams and see what happens tomorrow.

Thanks!
 
No, probably not roms but they are easy enough to check. If they are original masked roms they need to be changed at your first chance anyways.
Yes I would say its probably the same issue. The LS283's @ 1F & 2F seem to go bad often and also the ram at 3F occasionally. Piggybacking these usually work.
 
Here's my follow up if anyone cares. I piggybacked the 283's one at a time, and the 1F and 2F both made the problem worse. So I figured that's probably a decent sign that one or both of them were the culprit. Soldered in new ones (dang, should have bought sockets rather than soldering them in directly) and the game wouldn't even boot. Even though I couldn't see it, I discovered that I had a solder splash short to one of the traces that go between the pins. Fixed that, and I once again have a perfectly functioning ms pac.

Thank you guys for the help!!!
 
I know. It just didn't occur to me until tonight because this is the first time I've ever had to replace a non-socketed chip. But while I was doing it I was thinking "add sockets of all sizes to mouser shopping list". :)
 
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