The CPU board never boots.

Dead CPU: no clock signal at the 6809

Cause: The clock from the U9 ASIC (pins 81 and 82) through U5 (74LS14) isn't reaching CPU U4 pins 34 and 35.

Checks

• Check U4 pins 34 and 35 with a logic probe for activity.

Fix

• Replace U5 (74LS14); reseat the ASIC or replace its socket.

Systems

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

Related tips

• Signals a dead CPU board should show
• Dead CPU: isolate it from the other boards
• Why coils stay off until the CPU boots
• Reseating the U9 ASIC on a dead CPU board
• CPU board from an early game won't boot: ROM jumper W1
• Dead CPU: checking address and data lines
• CPU won't boot, blanking LED stays on: check the game ROM
• CPU board completely dead

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