The display doesn't work and both negative supplies read the same voltage.

-125 V and -113 V read the same and the display is dark

Cause: The 12 V zener D6 (D3 on WPC-95, 1N4742) that sets the gap between them has failed, which also kills transistor Q7 (MJE15030). An open R8 (4.7k ohm 5 W) gives the same symptom.

Checks

• Test D6/D3, Q7 and R8 (R43 on WPC-95).

Fix

• Replace the failed parts; better, rebuild the whole HV section.

High voltage section: work with the game unplugged.

Systems

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

Related tips

• Rebuild the high-voltage section of a 520-5047-00/-01/-02 supply
• Zener diodes D10 and D11 by DMD power supply revision
• Rebuilding the +100 V section of the power supply
• Cross the legs when MJE15030/15031 replace SDS201/SDS202
• Dot matrix display supply voltages
• Dot matrix display power connector pinout and voltages
• Rebuilding the dot matrix high voltage section
• Dot matrix display blank or faulty

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