Fitting MJE15030/15031 in place of SDS-201/202

Steps

• Note the pinouts: SDS parts are E-B-C, MJE parts are B-C-E.
• Put the MJE's left two legs in the board's second and third holes.
• Cross the right-hand leg under the other two into the first hole.
• Sleeve the crossed leg in heat shrink so it cannot short.

The display supply runs at about 100 volts DC; work with the game off and the capacitors discharged.

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Related tips

• Master display flickers, worst when showing 1: wrong zener diodes at ZR2 and ZR4
• Score displays weak, dim or dead with fuses good
• Lower the display voltage to 91 V to extend display life
• Fit 91 V zeners at Z2/Z4 to extend display life
• Upgrade R2/R5 and check R1/R4 in the display supply
• Display high voltage out of range
• Score displays light then dim or flicker
• All score displays dead

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part One, Clay Harrell (pinrepair.com)