Score displays are dead or faint.
Display high voltage out of range
Cause: A fault in the +/-100 V high-voltage section of the power supply.
Checks
- With outputs unplugged, black lead on J5 pin 1 (ground).
- J5 pin 3 should read -90 to -105 VDC.
- J5 pin 4 should read +90 to +105 VDC.
Fix
- If either is off, rebuild the high-voltage section.
The display supply runs at about 100 volts DC; work with the game off and the capacitors discharged.
Systems
Related tips
- All score displays dead
- Score displays weak, dim or dead with fuses good
- Lower the display voltage to 91 V to extend display life
- Score displays light then dim or flicker
- Score displays fade in a scrolling pattern
- Upgrade R2/R5 and check R1/R4 in the display supply
- Fit 91 V zeners at Z2/Z4 to extend display life
- Parts for rebuilding the System 3-7 display supply
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part One, Clay Harrell (pinrepair.com)