At start-up the game keeps loading balls into the upper tunnel, draining one and catapulting another, in an endless loop.

STNG keeps catapulting balls into the upper tunnel at start-up

Cause: The game can't load its guns. It should place one ball in the upper tunnel, one under each gun and keep three in the trough. Common causes: fuse F103 (3 A slow blow, upper diverter coil) blown, gun assembly optos, the under-playfield diverters, or a dirty or broken upper tunnel opto.

Checks

• Check F103 on the power driver board.
• Set both guns to Broken=Yes in the feature adjustments. If the game then starts normally, re-enable each gun in turn to find which causes the loop.

Fix

• Replace F103, or repair the gun optos, diverter or upper tunnel opto that is at fault.

Systems

• WPC DCS

Games

• Star Trek: The Next Generation

Related tips

• STNG won't start and keeps ejecting balls: fuse F103
• STNG cannon confused after a loom repair
• STNG: diverter coils lock on during play
• STNG: under-playfield diverter coils lock on during play
• Random multiball or game never ends on early opto troughs

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