First power-up, step 1: check the bottom-panel fuses

Steps

• With the game off, pull each bottom-panel fuse and test it out of the holder on continuity.
• Leave blown fuses out for now and note what each one feeds from its label.
• If the 6 V CPU lamp fuse is blown, test its bridge rectifier, since a shorted bridge blows its fuse.
• If the display fuse (about 60-69 V) is blown on 80/80A, suspect one of the four 1N4004 diodes on the power supply that rectify it.
• A blown 6.3 V GI fuse often means a shorted lamp socket on the playfield.
• On 80/80A, replace the orange 12 V logic filter capacitor while you are there.
• Finally, take the 28 V solenoid fuse out and set it aside before going on.

The bottom panel carries 120 V AC from the wall; unplug the game before touching the line filter, fuse block or transformers.

Systems

• Gottlieb System 80
• Gottlieb System 80A
• Gottlieb System 80B

Related tips

• Bottom-panel bridge rectifiers and fuses
• A bottom-panel fuse blows the moment the game is switched on
• Quick diode test of a bottom-panel bridge rectifier
• Identifying the leads of a bottom-panel bridge rectifier
• Bottom board fuses and what each feeds
• Check the 80B bottom-cabinet 10,000 mfd filter capacitor
• Check the bottom board and playfield fuses early
• System 80B ground lost at the transformer panel plugs

Source: Repairing & Upgrading Gottlieb System 80 Pinballs from 1980 to 1989, Part One, Clay Harrell (pinrepair.com)