Targets drop or a lock kicks out unexpectedly after a ball is served, and the game thinks it is in multiball with a ball trapped.
Expander game ejects or drops targets at the wrong time
Cause: A failed diode on one of the double-diode coils served by the solenoid expander board.
Checks
- Test both diodes on every coil wired through the expander, plus the diode on the expander board.
Fix
- Replace any faulty diodes; replacing all of them on those coils cured the reported case.
Systems
Related tips
- Drop target falls instead of the ball being kicked out (SEB games)
- Expander games: check the controlled-lamp power first
- Expander-driven coils fire in pairs: drop target coil fitted without its second diode
- Centaur uses its solenoid expander for the ball-to-playfield kicker
- Drop target coils misfire after LEDs or a new lamp driver: expander boards need bulbs
- How the solenoid expander board doubles up coils
- Test the coils behind the solenoid expander
- Replacing the hard-to-find 48 V expander relay
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)