The displays slowly fade in a rolling or scrolling way.

Score displays fade in a scrolling pattern

Cause: Failing high-voltage filter capacitors C1/C3 (100 MFD 150 V) on the power supply board.

Checks

• Inspect C1 and C3.

Fix

• Replace C1 and C3.

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

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

Related tips

• All score displays dead
• Score displays light then dim or flicker
• Display high voltage out of range
• Score displays weak, dim or dead with fuses good
• Upgrade R2/R5 and check R1/R4 in the display supply
• Lower the display voltage to 91 V to extend display life
• 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 Three, Clay Harrell (pinrepair.com)