The +62 V supply drops to around 12 V with the display connected.

+62 V collapses to about +12 V under load

Cause: Transistor Q3 (Q1 on WPC-95) has shorted; diode D3 may also be bad.

Checks

• Test Q3 and D3.

Fix

• Replace them, or rebuild the 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

• Outgassed displays and the 5 V supply
• -125 V reads about -140 V
• Dot matrix display supply voltages
• +62 V reads over 70 V
• Replace the whole display, not just the glass
• +5 V or +12 V missing at the display

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