The coil, its transistors and wiring all test good and the coil fires when its tab is grounded, but it never fires during a game.

Coil passes every test but still will not work in play

Cause: A logic chip ahead of the transistors (7408, 74LS273, 7402, 7407) or the 6821 PIA has failed.

Checks

• Use the logic chip map to find the gate, latch and PIA for that transistor pair, and probe their outputs with a logic probe.

Fix

• Replace the faulty chip, fitting a socket.

Systems

• Data East CPU Version 1/2
• Data East CPU Version 3
• Data East/Sega CPU Version 3b

Related tips

• PIAs or the EPROM are never selected
• Flippers and special coils all dead
• CPU still will not boot after the basics
• Which logic chips drive which solenoid transistor pairs
• Program runs but the PIAs never respond
• Battery voltage at the RAM but memory still lost
• Wrong speech and sounds play for callouts: battery-corroded CPU board
• New CPU board locks up when the coin door buttons are plugged in: reseat the PIA

Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Two, Clay Harrell (pinrepair.com)