During play the gun handle trigger often fails to fire the cannon; it needs a firm squeeze and quick release, or only fires when the cannon has swung toward the lower targets. The cannon tests fine in diagnostics and fires from the coin door test button.
Cannon often won't fire during play: adjust the at-mark switch
Cause: The game only allows a shot once the 'at mark' switch (the roller-lever microswitch on the cannon mechanism) says the cannon has swung out to the firing area. If that switch is badly positioned or its actuator worn, the game does not see the cannon at the mark in time.
Checks
- Run the gun test and watch the 'at mark' and 'home' switches change as the cannon moves.
- Check the ball-loaded switch in the cannon with a meter in every cannon position.
- Test the trigger switch in the gun handle out of the game.
- Check the wiring and diodes on the cannon switches for damaged or spliced wires.
Fix
- Adjust the 'at mark' switch position, moving it slightly toward the 'home' switch, and test in a game; repeat in small steps until the cannon fires normally.
- If the switch body is worn, slightly easing its mounting screws can free a sticking actuator; replace the switch if needed.
Systems
Games
Related tips
- Cannons or moving toys work intermittently or won't stop
- One switch triggers others and flippers act oddly: drop target switch wired backwards
Source: Pinball Repair help group!! (Facebook group)