A coil or CPU lamp fuse on the bottom panel is blown or blows again at power-on.

Bottom panel fuse keeps blowing

Cause: Usually a shorted bridge rectifier, most often the 6 V CPU lamp bridge, sometimes the coil bridge; a fuse can also simply age out.

Checks

• Test the bridge for that supply with the meter on diode test (see the bridge test entry).

Fix

• Replace a bad bridge with a 35 amp lug-style bridge, then fit the correct fuse.

The bottom panel carries 120 volt line power; unplug the game before touching the transformers, line filter or fuse block.

Systems

• Gottlieb System 1

Related tips

• Bottom panel fuses on System 1
• Coil, CPU lamp and GI supplies
• What is on the System 1 bottom panel
• All CPU controlled lamps are dim
• None of the CPU controlled lamps light
• No CPU controlled lamps light
• How power reaches a System 1 game
• Power supply bring-up, step 1: inputs

Source: Gottlieb System 1 Pinball Repair from 1977 to 1980, Clay Harrell (pinrepair.com)