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Mac II with no Nubus slots working - can another Mac II owner measure some voltages/resistances?


Well-known member
The only way I found these broken traces was studying the Bomarc schematics and checking that every pin on all those buffer chips went to where they're meant to. Good luck!
Thanks. I spent this morning checking continuity and all is confirmed with the schematics.

The only thing that is incorrect that I have found is with UG1 pins 11, 13, 15 & 17 don't go to RP7, but go to RP8. I also have a battery bombed Mac IIx board and double checked. UG1 Pin 11 goes to RP8 pin 5, 13 to 9, 15 to 3 and 17 to 1.

So I am unsure why I am not getting NuBus to work. This board may have other issues. I thought at first it might be a problem with ROM. There is no boot chime, and no video, similar to not having a ROM stick installed. I replaced the ROM socket.

I will keep digging. Thankfully this is an extra board.

I'm glad you were able to find your issue.


  • mac iix trace check.png
    mac iix trace check.png
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