One score display does not work properly while the others are fine.

Bally six-digit score display fault fixed by replacing transistor Q14

Cause: A failed transistor (Q14) on the display board.

Checks

• Swap the display into another position to confirm the fault follows the display, not the driver wiring.
• Follow a Bally display failure guide to work out which transistor matches the bad section, then test it.

Fix

• Replace Q14 (or whichever transistor tests bad) and reflow the display's header pins, which commonly crack.

Bally displays run on high voltage (around 190 V). Power off and let it discharge before handling the display board.

Systems

• Bally MPU AS-2518-35

Games

• Harlem Globetrotters On Tour

Related tips

• Bally -35: same digit positions dark on every display: open digit drive resistors
• Bally and Stern score display boards
• One digit missing on a score display
• Seven-digit and six-digit displays
• Score display digit parts by position
• First checks before repairing Bally score displays
• One or two score displays completely blank
• Making Bally and Stern 7-digit displays swap between makes

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