Change zener diodes Z2 and Z4 for longer display life
Replacing power supply board diodes Z2 and Z4 (1N4764, 100 V) with 1N4763 (91 V) makes the displays slightly dimmer but greatly extends their life.
The display supply carries about 100 V DC (plus and minus); keep fingers and probes off the master display board and power supply high-voltage section with the game on.
Systems
Related tips
- Fit 91 V zeners at Z2/Z4 to extend display life
- Run alphanumeric displays at 91 V for longer life
- Lower the display voltage to 91 V to extend display life
- Master display flickers, worst when showing 1: wrong zener diodes at ZR2 and ZR4
- Upgrade R2/R5 and check R1/R4 in the display supply
- All score displays dead
- Score displays light then dim or flicker
- Parts for rebuilding the System 3-7 display supply
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Three, Clay Harrell (pinrepair.com)