Finding a coil's driver transistor without a manual
Steps
- At the coil, identify the ground wire: the thinner wire on the lug with the non-banded end of the diode. Note its colours.
- Find that wire colour on the driver board connectors and write down the connector and pin.
- Unplug that connector and, with the meter on continuity, probe from that header pin to the metal tabs of the TIP transistors until you find the one it connects to.
Systems
Related tips
- Use the manual's coil/flasher chart to find driver transistors
- Always check the coil diode when a driver transistor has failed
- Constant power coil drivers Q8-Q13 and Q23-Q30
- A low resistance coil means checking its driver chain too
- Check every coil's resistance before first power-up
- The solenoid L/R select relay and transistor Q29
- Solenoid driver layout: 16 multiplexed plus 14 constant
- Bank select relay and CPU transistor Q29
Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Two, Clay Harrell (pinrepair.com)