Judging the logic filter cap by AC ripple

With the game on and the meter on AC volts across the filter cap leads, 0.300 VAC or more means the cap needs replacing. On System 3-6 even a new cap reads at least about 0.200 VAC because of half-wave rectification. A new cap on System 7 should read 0.100 to 0.200 VAC.

Systems

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

Related tips

• Replace the +5/+12 V logic filter capacitor
• Upgrade logic rectifier diodes D7 and D8
• +5 V logic low or noisy
• Leave the big lamp filter capacitor unless it is leaking
• Display supply low (under 90 V) after the resistors are changed
• Cross the legs when MJE15030/15031 replace SDS201/SDS202
• High-voltage supply rebuild parts, System 3 to 11C
• Fitting the high-voltage kit

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