Parts for rebuilding the System 3-7 display supply
Q1 MJE15030 (replaces SDS-201), Q3 MJE15031 (replaces SDS-202), Q2 MPSD52 (or 2N5401/2N5400), Q4 MPSD02 (or MPS-A42/MPS-A06), Z2/Z4 1N4763 91 V zeners, Z1/Z3 1N4730 3.9 V 1 W zeners (replace 1N5990), R2/R5 1.2K 1/2 W, R1/R4 39K flameproof, and C7/C11 (C1/C3 on System 7) 100 mfd 150 V.
The display supply runs at about 100 volts DC; work with the game off and the capacitors discharged.
Systems
Related tips
- Upgrade R2/R5 and check R1/R4 in the display supply
- High-voltage supply rebuild parts, System 3 to 11C
- All score displays dead
- Lower the display voltage to 91 V to extend display life
- Fit 91 V zeners at Z2/Z4 to extend display life
- Score displays light then dim or flicker
- Find a shorted display glass that blows F1
- Change zener diodes Z2 and Z4 for longer display life
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part One, Clay Harrell (pinrepair.com)