Some digits glow too bright while others are faint or missing, and the fault affects player 1 and 3 displays together (or 2 and 4).
Digits burning or faint on players 1 and 3 (or 2 and 4)
Cause: A bad 74154 on the CPU board (IC6 in a reported Black Knight case).
Checks
- Confirm the master display board is good (try another game or swap display cables).
Fix
- Replace the 74154.
Systems
Related tips
- Missing digit on one or more score displays
- F-14 Tomcat: left credit-display character scrambled
- Score displays dead but digits glow: bad wire in the CPU blanking plug (1J3)
- Seven-digit scoring on six-digit displays for green-ROM games
- Ball and credit displays show only even numbers after header work
- Displays have high voltage but stay blank
- CPU LEDs flash and go out but the score displays stay dark
- System 7 CPU digit display dead: check IC34 7447
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Three, Clay Harrell (pinrepair.com)