The CPU board never boots on the bench with good power.

Dead CPU: check the reset and IRQ lines

Cause: The reset line at 6809 CPU U4 pin 37 never goes high, usually from a failed U10 reset chip (34064); or the IRQ line is stuck.

Checks

• Meter U4 pin 37 at power-up: it should go from 0 V to about 4.5 V.
• U4 pin 3 (IRQ) should also start low then go high.

Fix

• Replace U10 (MC34064).

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• MC34064 watchdog at CPU U10: pinout and substitute
• What a WPC game reset is
• Dead CPU: checking address and data lines
• CPU board completely dead
• Dead CPU: isolate it from the other boards
• CPU board from an early game won't boot: ROM jumper W1
• Why coils stay off until the CPU boots
• Running a WPC CPU board on the bench

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Three, Clay Harrell (pinrepair.com)