Flippers never work in a game, or keep working after the game ends.

Flippers dead, or still live after game over: the flipper relay

Cause: The Z1 flipper relay on the driver board or its drive: 2N4401 transistor Q13 beside the relay, the 7402 at IC8, resistors R27 (4.7k) and R26 (10k), diode D1 (1N4001). The drive parts are the same on all System 3 to 7 boards. Relay faults are uncommon, so check this last.

Checks

• Diode-test Q13.
• Check IC8, R26, R27 and D1.
• With the driver board out, put a 9 V battery across the relay coil lugs (the two lugs separate from the other twelve); it should click in and out cleanly.

Fix

• Replace the failed part. The relay is a 4PDT, 6 V, 40 ohm type; MagneCraft W78CSX-1 is a suitable replacement.

Systems

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

Related tips

• Flipper relay does not click on in test
• No flippers at all: flipper relay K1 not pulling in
• Test a 2N4401 pre-driver with a meter
• Solenoid driver test at 2J9 and 2J11 with Leon's code
• One or a few coils lock on at power-up
• Diode-test the TIP120/TIP102 and 2N4401
• Flippers never work: flipper relay RY1 not pulling in
• CPU flipper enable relay RY1

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