All CPU-controlled lamps are dim, and on SEB games the expander relay buzzes instead of clicking.
Dim controlled lamps and a buzzing expander relay
Cause: A tired 6 V lamp bridge rectifier on the rectifier board, especially on games before Xenon.
Checks
- Measure the controlled-lamp supply; a low reading points to the bridge, its connector pins, or rectifier board resistor R2 (25 ohm, 5 W).
Fix
- Replace the lamp bridge with a 35 A, 400 V bridge rectifier.
Systems
Related tips
- None of the controlled lamps light
- No feature lamp voltage at TP1 (-18 board)
- How Bally controlled lamps are powered and switched
- No general illumination after a new rectifier board, fuses good: check the bulbs
- Finding a short that blows GI fuse F5
- Find a short that blows the 20 A GI fuse
- Solenoid expander relay buzzes or does not switch
- Expander games: check the controlled-lamp power first
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)