The master (credit/ball) display flickers, most of all when it shows a 1, even when it is the only display connected. Display pins have been reflowed.
Master display flickers, worst when showing 1: wrong zener diodes at ZR2 and ZR4
Cause: During an earlier recap and upgrade the zener diodes ZR2 and ZR4 in the display high-voltage supply had been replaced with the wrong parts, so the display supply was low (about 94 V instead of about 104 V).
Checks
- Measure the display high voltage on the power supply and compare it with the manual or repair guide.
- Check the values of any zener diodes or other parts replaced during earlier power supply work.
Fix
- Fit the correct zener diodes at ZR2 and ZR4 (here the originals were put back).
The display supply runs at around 100 V DC; work with the game unplugged and the supply discharged.
Systems
Games
Related tips
- Change zener diodes Z2 and Z4 for longer display life
- Fit 91 V zeners at Z2/Z4 to extend display life
- Score displays light then dim or flicker
- Upgrade R2/R5 and check R1/R4 in the display supply
- All score displays dead
- Lower the display voltage to 91 V to extend display life
- Parts for rebuilding the System 3-7 display supply
- Find a shorted display glass that blows F1
Source: Pinball Repair help group!! (Facebook group)