Several displays lose segments or digits right after a display was unplugged or swapped.

Display chips on the CPU board fail after swapping displays

Cause: The display was connected or disconnected with the game switched on, which nearly always takes out one or more of the CPU display chips: the 7448s at Z19, Z21 and Z23 or the 7404s at Z17, Z24 and Z26.

Checks

• Check those chips with a logic probe.

Fix

• Replace the failed chips, and only ever move displays with the power off.

System 80/80A displays run on about 60 V DC; switch the game off before unplugging or touching a display or its connector.

Systems

• Gottlieb System 80
• Gottlieb System 80A

Related tips

• Missing segment on one or more score displays
• Missing digit on one or more score displays
• Displays never show the digit 1
• Damage after the black and white plugs were swapped
• Scores show only a single 0 and the credit display is blank: failed 7404 at IC31
• Boot stops after the ninth LED flash: IRQ fault
• Gottlieb System 80: bottom segment missing on one display that follows it: replace Z1
• Blanking circuit parts: C32/C84, IC7, Q5/Q1 and IC23

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