A fuse blows at power-on or during play.

Finding why a fuse blows: start with which circuit

Cause: 120 V line fuse: shorted power cord or (rarely) transformer. 6.3 V lamp fuses: a shorted bulb or socket, or lamp wire on the frame. 30/50 V solenoid fuse (the most common): a coil locked on, low-resistance coil or shorted switch. Some 1970s Williams and Bally and 1950s Genco games have an extra fuse for a rectifier.

Checks

• Vacuum out the cabinet first; loose parts lying across wiring often cause the short, and keep any hardware you find.
• Identify which fuse is blowing and trace only that circuit.

Fix

• Use a plug-in circuit breaker instead of fuses while chasing the fault.

Systems

• Electro-mechanical

Related tips

• Solenoid fuse blows
• A fuse blows as soon as a game is started
• Check fuse ratings before the first power-up
• Make a plug-in circuit breaker for chasing blown fuses
• Bally EM: GI dims during play
• Fuses to keep for EM games
• Where EM fuses are
• Game won't start and score motor won't run: bad fuse clips on the 25 V fuse

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