On a Bally 6-digit score display one segment (for example the bottom or bottom-left) is missing on all digits, and a new decoder chip does not help.
Bally 6-digit display: one segment out on every digit, find the bad driver by swapping
Cause: The segment driver transistor for that segment had failed. Replacement transistors pulled from other old display boards can be bad too, which makes the fault look like it is somewhere else.
Checks
- Swap the suspect segment driver transistor with the one for a working segment: if the missing segment moves, the transistor is bad.
- Check the glass for cracks and broken pins, and reflow the header and glass pins.
Fix
- Fit a known-good (new) transistor of the correct type in the bad segment position. If it still fails, check that segment's resistors.
Score displays run on high voltage (around 190 V): unplug the game and let it discharge before touching the display boards.
Systems
Related tips
- Bally score display looks gassed with good voltages: replace its 4543 decoder chip
- Bally 7-digit display misbehaves wherever it is fitted: replace the decoder chip
- Bally 6-digit display: the decoder chip should be E-620-38 (4543)
- All displays show strange scores (one bad decoder)
- One digit missing on a score display
- Bally and Stern score display boards
- Score display digit parts by position
- One segment always lit on a display
Source: Pinball Repair help group!! (Facebook group)