The 60 V and/or 42 V display supplies are present with J3 unplugged but vanish once the displays are connected; the 60 V fuse may blow.

60 V and 42 V disappear when the displays are connected

Cause: A shorted score display, which is fairly common.

Checks

• Refit the 60 V fuse on the bottom panel.
• Unplug all score display connectors except one (Black Hole and Haunted House have one in the playfield too), power up and check 42 V and 60 V.
• Add one display at a time, powering off between each, until the voltage drops.

Fix

• Repair or replace the display that pulls the voltage down.

The System 80/80A power supply makes about 60 V and 42 V DC for the displays; keep fingers off the board and connectors with the game on.

Systems

• Gottlieb System 80
• Gottlieb System 80A

Related tips

• The display voltages to check
• System 80 schematics' 'offset' voltages are DC bias for the display filaments
• Score displays flicker
• Flickering displays and erratic pops from a poor J3 ground
• Which System 80 power supply boards are interchangeable
• First power-up, step 3: run the power supply on its own
• Tie the 80/80A power supply logic ground to its heat sink plate
• Original 80/80A power supply design overheats CR7

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