Score motor won't stop at a home position, or stalls part-way and freezes the game.

Score motor overruns or freezes: worn home switch

Cause: The home switch (usually 1C or 4C on Gottlieb) keeps the motor running between home positions. Each time it opens, the motor's collapsing field throws an arc at about twice the supply voltage, so it pits and drifts out of adjustment. Worn, it can let the motor overrun; dirty, it can fail to carry the motor to the next home.

Checks

• Watch the switch as the motor turns: a bright arc as it opens is expected, but look for pitting and a poor gap.

Fix

• File the contacts clean and set the gap. Do this on every EM you service.

Systems

• Electro-mechanical

Related tips

• Why the score motor home switch arcs on opening only
• Check the score motor switches before power-up
• EM score motor will not stop
• Score motor doesn't move to its next home position
• A score motor that won't stop is rarely the motor's fault
• Score motor switch numbering (Gottlieb and Bally)
• Getting at score motor switches, and slowing a sequence down
• Finding a Gottlieb score motor switch from its schematic name

Source: Repairing Electro-Mechanical (EM) Coin Operated Games to 1978, Part Two, Clay Harrell (pinrepair.com)