The main fuse in the cabinet blows the moment a new one is fitted, often after a power surge in the building.

Main cabinet fuse blows instantly after a power surge: shorted varistor

Cause: The surge-protection varistor (a green disc) inside the line filter box had shorted. It is meant to short above about 200 V to protect the game, and takes the fuse with it.

Checks

• Unplug the game, open the metal line filter box in the cabinet and inspect the green disc; a failed one is often cracked or blown out on the back.

Fix

• Replace the varistor (part number 5017-09044-00 was given).
• As a temporary measure it can be cut out so the game runs, but it should be replaced, and a surge-protected power strip is worth adding.

This is in the line voltage (120 V) input. Unplug the game from the wall before opening the filter box.

Systems

• WPC Fliptronics

Games

• Twilight Zone

Related tips

• Main fuse in the power switch box blows at switch-on: shorted varistor
• Shorted or open bridge rectifiers
• Burned power driver board traces at the header feeding AC to the Fliptronic board
• Game dead after a lightning strike or surge
• F116 blows a few seconds after power-up with a new clock board: uncut header pins
• Won't start after a power surge, 5 V reads very low: failed C4 on the power driver board

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