Pop bumpers, slingshots and other special solenoids do not fire after a first-generation System 11 CPU board is put in a System 11A game.

Special solenoids dead after fitting an early System 11 CPU in a later game

Cause: High Speed, Grand Lizard and Road Kings boards have no ground on CPU connector 1J18 pins 6 and 7, which the later special solenoid circuit needs.

Checks

• Check which CPU board is fitted (a seven-segment LED on the board means first-generation System 11).
• Check for ground on 1J18 pins 6 and 7.

Fix

• Run a ground wire to 1J18 pins 6 and 7, or fit the correct generation of CPU board.

Systems

• Williams System 11
• Williams System 11A

Games

• Grand Lizard
• Road Kings

Related tips

• How System 11 A/C switched solenoids work
• Lizard eye flashers locked on, then not flashing: bad drive parts and a missing resistor
• The six special solenoids (pops, slings, kickbacks)
• No plug at CPU 1J18 means CPU-controlled special solenoids
• Pop bumper or slingshot machine-guns or locks on (Fire! and earlier)
• Special solenoid signal path, chip by chip
• Whole groups of coils or all flashers dead: A/C select relay stuck
• Controlled solenoids 9-16

Source: Repairing Williams System 11 Pinball 1986 to 1990, Deel 1, Clay Harrell (pinrepair.com)