The MPU restarts its LED flash sequence during play, especially when flipping.

Game reboots during play from slam switch noise

Cause: The coin door slam switch closing, or its long wires picking up flipper coil noise.

Checks

• Check the slam switch for a closed or bent contact.

Fix

• Disable the input by cutting the slam switch wire where it lands on MPU J3 pin 16, the lowest pin of that bottom-right connector.

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35

Related tips

• Globetrotters reboots during play (GI stays on)
• Game reboots at random: R11 heating Q5
• What each MPU LED flash proves
• MPU boots only when U9 pins 39 and 40 are shorted
• MPU LED locked on with no flicker: likely causes
• MPU stops before the seventh flash: check the 43 V at R113
• Good MPU stays LED-on with a PC power supply
• MPU reboots right after the seventh flash

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)