The backbox general illumination is off.

Backbox GI out

Cause: F8 has blown, or the A relay's normally closed contact is out of adjustment.

Checks

• Check F8 (10 A fast-blow) on the A12 panel.
• Check the A relay contact closes with the relay at rest.

Fix

• Replace F8, or adjust and clean the A relay contact.

Systems

• Gottlieb System 3

Related tips

• A relay blanks the backbox GI on purpose
• Bulbs burn out fast: 110 V jumper plug fitted
• DC supplies from the transformer panel
• AC windings from the transformer
• Boots to game over, then lamps and switches are dead
• A12 transformer panel fuses F3 to F7
• A12 transformer panel fuses F8 to F11
• Game won't boot: failed vertical fuse holder

Source: Repairing Gottlieb System 3 Electronic Pinball Games from 1989 to 1996, Clay Harrell (pinrepair.com)