A slingshot or pop bumper does nothing.

Slingshot or pop bumper will not fire (System 11)

Cause: Either the coil output circuit or the switch input circuit has failed.

Checks

• Run the solenoid test. If the coil fails there, ground the coil lug, the CPU connector pin and the TIP122 tab in turn, as for any coil.
• If it works in the test, start a game or test mode (special solenoids are only enabled then) and briefly ground the switch terminal and the switch input pin on the CPU connector.
• If grounding the CPU input pin gives nothing, repair the CPU/driver board.

Fix

• If grounding the switch terminal fires the coil, clean and gap the switch contacts and check neither side of the switch is grounded.

Systems

• Williams System 11
• Williams System 11A
• Williams System 11B
• Williams System 11C

Related tips

• 50 V coil dead on an early System 11 game
• Sling or bumper locks on at power-up (System 11)
• System 11 coil outputs
• How the System 11 A/C bank select works
• How System 11 special solenoids work
• A-bank coil not working
• C-bank coil or flasher not working
• Sling or bumper locks on when a game starts

Source: Pinball Machines: How They Work & Troubleshooting, Norbert Snicer