Players 2 and 4 show scores; players 1 and 3 do not.

Only even-numbered score displays show numbers

Cause: A bad 5101 RAM on the MPU board.

Checks

• Swap in a known-good 5101.

Fix

• Replace the 5101.

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35

Related tips

• Flickering score displays
• Score display J1 to MPU J1 connections
• All digits on all displays show 2s or 7s
• One score display dark: poor contact at MPU J1 pin 20
• A display not working from MPU or sound board faults
• First checks before repairing Bally score displays
• Same digit missing or stuck on every display
• All 7-digit displays show a dim first digit and comma

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)