A cannon still misbehaves after its wiring loom is replaced.

STNG cannon confused after a loom repair

Cause: A dead cannon opto (which tells the game a ball is loaded), or a cannon plunger that has become magnetised and sticks in the fired position, blocking the opto.

Checks

• Check each cannon opto in switch test.

Fix

• Replace a dead opto.
• Replace a magnetised plunger.

Systems

• WPC DCS

Games

• Star Trek: The Next Generation

Related tips

• STNG keeps catapulting balls into the upper tunnel at start-up
• STNG won't start and keeps ejecting balls: fuse F103
• STNG: diverter coils lock on during play
• STNG: under-playfield diverter coils lock on during play

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Three, Clay Harrell (pinrepair.com)