How many coils the driver board can fire
The driver board runs only eight devices: three sound or chime lines, the knocker, the outhole kicker and three game-specific coils. A game needing more borrows driver lamp transistors Q3 or Q4 to pre-drive an under-playfield 2N5875, so at most five game-specific coils are CPU fired.
Systems
Related tips
- Which driver transistor fires which coil
- Testing the 2N6043 coil drivers
- Early driver boards lack isolation diodes
- Diode test of driver board 74175 chips
- Driver transistors Q1-Q4: relays and spare outputs
- Testing MPS-A13 and MPS-U45 driver transistors
- Spare transistors for System 1 boards
- Meter transistor tests are not conclusive
Source: Gottlieb System 1 Pinball Repair from 1977 to 1980, Clay Harrell (pinrepair.com)