One score reel stays off zero, and the motor may run on.

EM score reel will not reset to zero

Cause: Dirt or old grease binding the reel mechanism, a broken reel part, misadjusted reel switches, or a faulty switch on the reel's relay in the backbox.

Checks

• Unclip the reel from its bracket and step it to zero by working its solenoid by hand; if the motor stops, the reel is the problem.
• Look for a broken switch or wire on the reel.
• Operate the reel solenoid and watch the reel switches open and close; compare with a reel that works.
• Find the matching relay in the backbox (often labelled 10, 100 or 1,000 point) and check its switches by hand.

Fix

• Clean the reel mechanism (dismantle only if needed; it is full of small washers and springs).
• Clean and adjust the reel and relay switches.

Systems

• Electro-mechanical

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Source: Pinball Machine Care & Maintenance, Bernard B. Kamoroff (Bell Springs Pinball Alley)