Thanks. I have installed new ribbon cables except for the one between the sound board and the aux. sound board, still looking for one of those. Both ribbon cables on the cpu were bad, pin 1 on both of them, probably caused by folks squeezing the cable to pull it off.
I have repinned the .156 connectors, new EPROMs, new ram, checked traces, reflowed solder, etc. I am going to swap cards between my Super Mario Bros. Mushroom World and Gladiators one at a time and see if I can identify which board, if any, is causing the problem. I’ll start with the ribbon cable.
The cpu and display driver continues to work when the sound board locks up and the game plays fine, just no sound, so I don’t think the problem is coming from the cpu but anything is possible. I’ll direct some heat on the board to see if it could be heat related but first I’ll see if I can identify which board is the problem.