Replace the +5/+12 V logic filter capacitor

Steps

• Locate C15 (System 3-6, originally 12,000 mfd 20 V) or C10 (System 7, 18,000 mfd 20 V) on the power supply board.
• Use any new capacitor of 10,000 to 18,000 mfd at 16 V or more; use 15,000 mfd or more on games with three or four flippers.
• If fitting a radial snap-in cap, lay it flat on the board with its leads facing down, glue it with silicone (and a tie wrap if possible) and wire it to the pads.
• Do not stand a tall snap cap up on its leads, or drill the board for it; vibration will crack the joints or the glue.

Systems

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

Related tips

• Judging the logic filter cap by AC ripple
• Leave the big lamp filter capacitor unless it is leaking
• Upgrade logic rectifier diodes D7 and D8
• Spare diodes, capacitors and resistors for System 3-7
• +5 V logic low or noisy
• 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

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