Spy Hunter background glitch

LyonsArcade

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Hi folks;
I've got a Spy Hunter i've been messing with forever. Power supply puts out good voltages, I've got 5.1 volts at the chips on the board stack. I cleaned all the chips and reseated them, and bought new SCSI cables from Bob Roberts and installed them.

Game plays great, and passes self test (I guess, it just cycles through the color screens?)... but when you're playing, every few seconds a piece of the background shows up in the wrong place. For instance you'll be driving down the road and they'll be a tree in the road! Little blocks of the background in the wrong area. Makes it pretty hard to play!

Any ideas? I've heard the CPU pcb controls the backgrounds. Does this sound like a Ram problem the self test wouldn't pick up?
 
i think i've ran into something very similar. I forget the positions on the pcb, but there are 2 24 pin rams. One near the processor, and the other near the top of the pcb. The one near the top is the one to look at. If its not a 58725 (ie if its a 6116 or 2116) it'll glitch like that. Took me forever to finally run that down. That ram is the first one i'd try replacing.
 
Alright, thanks for the tip. Was yours heat related? For instance, tonight I took it all apart, resocketed the chips again, and SWITCHED the two 6116's. I believe one is right next to the processor and handles the battery memory, correct? I swapped it with the other 6116, and put everything back together. Popped the board back in, and everything was fine for a couple quick games, then the bad spots in the background started popping up a bit here and there again. Seemed better, though! Maybe that confirms your theory, hmmmmmm. I'll have to check around and see if I can find a parts board I can scavenge one off of to try out. I hate to order 1 chip from Bob, I just ordered stuff from him two days ago.
 
it wasn't heat related i don't think, but it did get worse when i played it. You could see it if you looked closely at the edge of the road during attract, every once in a while a piece would be goofed up.
 
Well, I ordered the m58725p chip, put it in, and just like before, everything was fine for about an hour, then it started acting up again. So now I've got a tested fine power supply, new ribbon cables, and replaced the ram chip on the cpu. If I turn the game off for quite a while it's fine when you first turn it on, but after it warms up the background starts having small areas in the wrong place. It's pretty sporadic, about every 10 or 20 seconds it does it right now.

Anybody else have any ideas? Any MCR experts out there?
 
try cleaning the chip legs on the 6116 and the 58725 on the video board, and the 93419's too. make sure they're not bent outward any at all - that sounds like a weak socket that's getting hot and not making good connection.
 
I cleaned and reseated all the chips twice now, no dice. I can eliminate the video board, can't I, since the background is handled on the CPU board?

I think I might try replacing the ram sockets on the cpu board next, I don't know. Does heat change how the socket makes contact? (I really don't know, I'm asking, lol)
 
Know anyone nearby that has a boardset? You could swap one board at a time and isolate the issue to at least the offending board pretty quickly...
 
I cleaned and reseated all the chips twice now, no dice. I can eliminate the video board, can't I, since the background is handled on the CPU board?

I think I might try replacing the ram sockets on the cpu board next, I don't know. Does heat change how the socket makes contact? (I really don't know, I'm asking, lol)

Never eliminate the video board as the problem on a spyhunter.
 
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