Cinematronics CPU board problem

Has anyone ever been doing Cine CPU troubleshooting using an exorciser setup and found 100% of the signatures to be correct but the board still won't run? I'm having this problem with a Rip Off CCPU. It is not a mod'ed board (meaning it uses 2716 eprom's). I've tested or replaced about 30 chips including the eproms, a few bipolar d_roms, some 74LS163 counters that were messed up, a few gates, all the 74LS377's, the 74LS181's, the ram chips, all of the original chip sockets, and so on. Like I said, all the sigs are perfect. I tried the "load loop timer" test, the "spac" test, the "no-op" test, and the standard test. I've done them all 3x or more. The old original docs are loaded with numerical errors but I have sorted them all out already. The PCB is very clean, no open traces that I can find, no missing pads, no broken resistors or caps, etc. It is visually perfect. All the clock signals are perfect as well.

I had a stack of about 10 old CCPU's and I finally decided to repair them all. I whipped through the batch and fixed 6 of them within a couple of days. I'm now down to just 3 left. I probably should move on to the last 2 boards and come back to this one last, but I don't want to let it beat me. I'll keep at it even if I have to replace every last chip on the whole board one at a time if that's what it takes. At this point, I'm simply out of ideas.

One of my other boards that doesn't work also has all good signatures as well. I can only hope that it doesn't turn out to be the same nightmare all over again. I don't really understand how all of the signatures can be correct and the roms all verified and the ram replaced with known-good chips and the thing still won't run.

Any thoughts or suggestions?

William Boucher
http://www.biltronix.com/arcade_01.html

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Received on Sun Jan 18 22:37:23 2009