Coils 1-8: connector, transistors, PIA pin
Driver is the TIP120 (fit a TIP102), pre-driver the 2N4401, gate a 7408 whose two inputs are the PIA line and blanking; the PIA outputs read low in attract mode. Coil 1: J11-4; driver Q15, pre-driver Q14; gate IC1 out 8, in 10/9; PIA IC5-2. Coil 2: J11-5; driver Q17, pre-driver Q16; gate IC1 out 11, in 12/13; PIA IC5-3. Coil 3: J11-7; gate IC1 out 6, in 4/5; PIA IC5-4. Coil 4: J11-8; driver Q21, pre-driver Q20; gate IC1 out 3, in 1/2; PIA IC5-5. Coil 5: J11-9; driver Q23, pre-driver Q22; gate IC2 out 8, in 10/9; PIA IC5-6. Coil 6: J11-3; driver Q25, pre-driver Q24; gate IC2 out 11, in 12/13; PIA IC5-7. Coil 7: J11-2; driver Q27, pre-driver Q26; gate IC2 out 6, in 4/5; PIA IC5-8. Coil 8: J11-1; driver Q29, pre-driver Q28; gate IC2 out 3, in 1/2; PIA IC5-9.
Systems
Related tips
- A low resistance coil points to a bad driver transistor
- What each 6821 PIA does
- How a coil is switched on
- Coil locks on and new transistors don't help: a failed 7408 on the driver board
- Driver board transistors and what they drive
- Slings and pops all burned at once: CPU lock-up from the 40-pin interconnect
- Why the solenoid and switch PIAs fail most
- Spare transistors for driver board and power supply
Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Three, Clay Harrell (pinrepair.com)