The ball-in-play and credit displays only ever show even digits: ball 1 shows 0, balls 2 and 3 both show 2, and adjustment numbers show only even values. Everything else plays normally.

Ball and credit displays show only even numbers after header work

Cause: After the display connector headers on the CPU board were replaced, one header pin was no longer connected because its trace or pad had lifted, so one display data line never reached the displays.

Checks

• Check continuity from each display header pin on the CPU board back to its trace and chip.
• Look closely at pads around any replaced headers for lifting or cracks.

Fix

• Repair the broken connection with a jumper wire from the header pin to the point where the trace is still good.

Systems

• Williams System 7

Games

• Laser Cue

Related tips

• Displays have high voltage but stay blank
• Score displays dead but digits glow: bad wire in the CPU blanking plug (1J3)
• Digits burning or faint on players 1 and 3 (or 2 and 4)
• Whole digits missing
• CPU LEDs flash and go out but the score displays stay dark
• Game powers up in audit mode instead of attract mode
• Game powers up in audit mode
• System 7 CPU digit display dead: check IC34 7447

Source: Pinball Repair help group!! (Facebook group)