As soon as the game is switched on, the right slingshot locks on until the 2.5 A solenoid fuse blows. With that coil unplugged, the lower left pop bumper is also dead, though it fires when its transistor tab is grounded.

Right sling locks on at power-up and a pop is dead: bad 7402 at U45

Cause: The 7402 NOR gate chip at U45, which drives these special solenoids, had two bad gates: one stuck on (the sling) and one dead (the pop).

Checks

• Rule out the switches, the switch capacitors, the coil diode and the driver and predriver transistors.
• Check the 7402 outputs for those circuits with a logic probe, or swap in the matching 7402 from U50 to test.
• After repairing these circuits, test the blanking: with the solenoid fuse removed, briefly short two legs of a CPU EPROM; lamps and displays should blank at once.

Fix

• Replace the 7402 at U45 (socket it).

Systems

• Williams System 11

Games

• High Speed

Related tips

• Coil fires when tested but not in game play: TTL driver chip
• Flippers and special coils all dead
• Diverter coils dead and flippers live at game over: 7402 at U50
• A coil or flasher comes on and stays on at power-up
• Damage after the black and white plugs were swapped
• Logic chips for the special solenoid transistor pairs
• How a coil or flasher is switched: PIA to TTL to pre-driver to driver
• Stern SB-100 sound board screeches until a game sound plays

Source: Pinball Repair help group!! (Facebook group)