(Topic ID: 163953)

Bally / Stern MPU boot issue

By TZ

7 years ago



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    #1 7 years ago

    I need help getting MPU to boot. Reset section works OK, but I can't get U9 pin 5 to pulse (CPU won't run).

    I have been troubleshooting per Clay's guide and have reached the point where the CPU is not running, pin 5 = low on my logic probe. I have swapped in a couple of different 6802's with no help. I am going to replace the socket hoping that will help; not sure what else to try....

    #4 7 years ago
    Quoted from barakandl:

    oh and the 6802 CPU is not going to work too. must be 6800

    Good to know.

    I will find a known working 6800 and test again. I can remove the socket and solder in some new machined sockets, but I really don't think that is the issue since it is factory and has not been disturbed.

    #5 7 years ago

    I pulled all of the chips except for U9 and U11. I put in a good U9 (6800) from a working machine. Now U9 pin 5 remains High. Clock pins 3, 36, and 37 pulse. I'm guessing next step is re-socket U9?

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