The flippers and a few coils work, but a group of coils further along the playfield do not.
Flippers and some coils work, others are dead
Cause: A break in the yellow coil power wire that daisy-chains from coil to coil, cutting power to every coil after the break; or a bad connection between MPU J4 and SDB J4 that disables coils 1 to 4.
Checks
- In attract mode, put the black probe on cabinet ground and the red on each dead coil lug; expect about 43 V DC on both lugs (page 18).
- Voltage on only one lug: the coil winding is open. None on either lug: follow the power wire back to the last coil that has it.
- If the coils have power, inspect SDB J4 and MPU J4 for cracked header solder joints and worn .100" pins.
Fix
- Repair the broken power wire, replace the open coil, or reflow the header and repin the J4 connector.
Systems
Related tips
- No coils work at all
- How Bally coils are switched
- Test the coils behind the solenoid expander
- Solenoids fire out of order in solenoid test
- Find a shorted coil circuit by plugging SDB connectors one at a time
- Wrong coil fires or a coil never fires
- Coil locks on at power-up or stays on
- Solenoid selection: four MPU lines decoded by a 74154
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)