When the last ball drains, the match relay pulls in as it should but never releases, so the score motor keeps running.

Score motor runs on at game over: end game relay not pulling in

Cause: The match relay could not pull in the end game relay (XB), because the switches that energise that relay were dirty. The end game relay is what interrupts the match relay and the scoring.

Checks

• On the schematic, follow the match relay circuit to the end game relay and find every switch in its coil circuit.
• Check that the end game relay pulls in when the match sequence runs.
• The 'on ball rack' switch on the match relay circuit is in the stack of three switches on the outside of the ball trough by the gate; also check the motor run switch on the match relay for a gap that is too small.

Fix

• Clean and adjust the switches that energise the end game relay.

Unplug the game before working on relays: parts of an EM's wiring carry line voltage.

Systems

• Electro-mechanical

Games

• Slick Chick

Related tips

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• Next ball sometimes not served after a drain: C relay path switches, then new rubbers
• Game resets but the outhole relay never fires: feed wire hanging by a strand
• Game keeps cycling the reset and starts in Game Over: dirty P5A switch and shorted wires

Source: Pinball Repair help group!! (Facebook group)