Version 3 CPU fires special coils once per switch closure
From Back to the Future the CPU runs the special coils itself and fires each one only once, for a set time, however long its switch stays closed. A stuck switch no longer locks a coil on.
Systems
Related tips
- Special solenoids: switch-fired on CPU Rev 1/2, CPU-fired on Rev 3
- Special solenoid signal paths SS1-SS6 on the CPU board
- A coil has power but never fires
- Check every coil's resistance before first power-up
- Several bank-switched coils or flashers dead, or firing the wrong device
- Testing the legacy special-solenoid circuit at CN18
- Special coil stays on even after replacing its driver chain (Rev 3)
- Bank select relay and CPU transistor Q29
Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part One, Clay Harrell (pinrepair.com)