How a coil or flasher is switched: PIA to TTL to pre-driver to driver
Every coil has power on it all the time; the game fires it by switching its ground side. The 6821 PIA drives a 7408 or 7402 TTL gate, which turns on a 2N4401 pre-driver, which turns on the TIP122/TIP102 driver. For the heaviest coils on the PPB board, that TIP122/TIP102 in turn drives a TIP36c. The stages exist so the 5 V logic can control the high-current coil ground, and a failure at any stage can lock a coil on.
Systems
Related tips
- 50 V coils use PPB TIP36c transistors, pre-driven from the CPU board
- Three-stage drive for 50 V coils
- Solenoid driver transistor positions on the CPU and PPB boards
- A coil or flasher comes on and stays on at power-up
- Which logic chips drive which solenoid transistor pairs
- Lamp column still dead after a new TIP42
- Coil fires when tested but not in game play: TTL driver chip
- CPU and driver board transistors by position
Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Two, Clay Harrell (pinrepair.com)