In solenoid test only the continuous solenoids (outhole gate, coin lockout, flipper enable relay) work; every momentary solenoid stays dead, yet each one fires if its driver transistor tab is grounded. Fuses are good.
Bally -35: momentary solenoids all dead but fire when grounded: solenoid driver U3
Cause: The MPU sends a 4-bit code to the solenoid driver board, where a decoder chip (U3) selects which momentary solenoid to fire. Here U3 had failed. A bad pin on the data lines between the boards gives the same symptom, and can also kill sound.
Checks
- Check the top pins of the MPU's lower-left connector and the matching pins on the solenoid driver board connector (the data bits and the coil/sound select line); repin any that are corroded or loose.
- If the connections are good, test or replace U3 on the solenoid driver board.
Fix
- Replace U3 on the solenoid driver board (socket it).
Systems
Related tips
- Arcing between J3 pins on the solenoid driver board and displays out
- Pop bumpers fire nonstop after a solenoid expander swap: board jumper set wrong
- Coil in the drop target assembly is always on: burnt trace on the solenoid driver board
- Kickout coil burns up in attract mode: driver transistor, resistor and the CA3081 at U3
- Bally: flipper relay won't fire in game: hairline trace break that still beeps
- Top lane gate never opens, even in solenoid test: failed driver transistor
- Saucer fires at power-on and blows the playfield fuse: wrong coil killed its transistor
- One flipper dead with full voltage at the coil: cracked joints at the flipper relay
Source: Pinball Repair help group!! (Facebook group)