What the coil diode does and how a bad one shows up
Every Data East/Sega coil must have its own diode. When a coil switches off, its collapsing field kicks back a spike of up to about twice the supply voltage, and the diode keeps that spike off the boards. A shorted diode blows the coil fuse. An open or missing one gives odd play and resets as the board absorbs the spike, and can kill the driver transistor.
Systems
Related tips
- Testing a coil diode
- Testing the diode on a coil
- Which way a coil diode goes
- Which way a coil diode goes
- Always check the coil diode when a driver transistor has failed
- Testing a coil diode on the driver board
- Testing the diodes on a flipper coil
- Coil diode and wire orientation when replacing a coil
Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Two, Clay Harrell (pinrepair.com)