OutRun very strange fault

parism

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Hey guys, it took me a long time to get this PCB working, learned a lot, but this little problem remains. Take a look at the video and notice how the sky jumps as soon as the go green light turns on.

https://www.youtube.com/watch?v=-J5heD6q2bA

Anyone ever seen and fixed this?

I have a logic probe, a logic pulser, a logic comparator (HP) and an oscilloscope so if you have the answer let me know!

Thanks,

paris
 
That is truly weird and a very specific failure. Hopefully some of the great gurus here can steer you in the right direction. Good luck.

Scott C.
 
Small update, the fault is on the CPU board, based on some pcb exchange experiments with a known working board.

Will update this thread if I make any progress...
 
I would have sworn the problem was in scroll RAM on Video Bd. There really isn't anything on CPU Bd that could cause this. Does it do anything else or is this the only problem at start?
 
The game passes the memory test (I have used the one from the OutRun SDK). The pcb had some RAM on the cpu board that I had to replace, one IC in the road section of the cpu board, then it would run fine for 45 min then the road would get stuck in whatever direction it happened to be at that time. Restart would fix it but it would crash again at progressively shorter times. That took me a while to figure out but it turned out to be a faulty 68k cpu (long story). In any case, this seems to be the only fault now. Luckily I can have the pcb on the bench and start a game, so I don't need to have it in the cab to troubleshoot. I will update when something comes up, I need to find a way to reproduce this error which will point me to the right IC....
 
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