Signals a dead CPU board should show
On a working board the address and data lines on U4, U6, U9 and the buffer chips toggle at about 4 V peak to peak; any line not toggling should sit at a solid high or low, never floating. U4 pins 34 and 35 carry the 2 MHz clock from ASIC pins 81 and 82. Pins 37 (reset), 3 (IRQ) and 32 (R/W) must be active as well.
Systems
Related tips
- Dead CPU: isolate it from the other boards
- Dead CPU: no clock signal at the 6809
- Reseating the U9 ASIC on a dead CPU board
- Dead CPU: the order to replace chips
- Dead CPU: checking address and data lines
- What is on the WPC CPU board
- CPU board completely dead
- Dead CPU: check the reset and IRQ lines
Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part One, Clay Harrell (pinrepair.com)