Check every coil's resistance before first power-up
Steps
- With the game off, set the meter to its lowest ohms range.
- Measure across each coil's lugs. Expect 2.5 ohms or more.
- If a coil reads under 2.5 ohms, unsolder one wire and measure again.
- Still low: the coil (or its diode) is bad, and its driver transistor may be too.
- Now normal: the coil is good and its driver transistor is shorted.
- To rule out the diode, cut one diode lead free of the lug and re-measure.
Systems
Related tips
- Constant power coil drivers Q8-Q13 and Q23-Q30
- A low resistance coil means checking its driver chain too
- A coil has power but never fires
- A coil or flasher comes on and stays on at power-up
- Special coil locks on only when a game starts or diagnostics begin (pre-Rev 3)
- Always check the coil diode when a driver transistor has failed
- Finding a coil's driver transistor without a manual
- Firing a coil by grounding its TIP122/TIP102 tab
Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part One, Clay Harrell (pinrepair.com)