Bank select relay and CPU transistor Q29
With the select relay off, solenoid power goes to the L bank only. When CPU transistor Q29 energises the relay, power moves to the R bank and the L bank is dead. Flasher returns pass through a sandstone resistor and a diode on the PPB, coil returns through a diode, then on to the CPU driver.
Systems
Related tips
- The solenoid L/R select relay and transistor Q29
- Testing the L/R select relay by grounding Q29
- L/R relay never clicks: test Q29
- All L or all R bank coils/flashers dead: PPB relay K1
- L/R relay burnt or intermittent
- Time Machine to The Simpsons swap the L and R banks
- Under-playfield relay boards and the PPB board
- Always check the coil diode when a driver transistor has failed
Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part One, Clay Harrell (pinrepair.com)