Special solenoid signal path, chip by chip
Each special solenoid runs from a 6821 PIA pin through U49, then a 7402 (U45 or U50), a 2N4401 pre-driver and a TIP122 driver. SSa: U38 pin 39, U45, Q74, Q75. SSb: U41 pin 39, U45, Q70, Q71. SSc: U41 pin 19, U45, Q72, Q73. SSd: U38 pin 19, U45, Q68, Q69. SSe: U54 pin 19, U50, Q76, Q77. SSf: U54 pin 39, U50, Q78, Q79.
Systems
Related tips
- The six special solenoids (pops, slings, kickbacks)
- Controlled solenoids 9-16
- How System 11 A/C switched solenoids work
- Special solenoids dead after fitting an early System 11 CPU in a later game
- Whole groups of coils or all flashers dead: A/C select relay stuck
- Lizard eye flashers locked on, then not flashing: bad drive parts and a missing resistor
- One pop bumper weak and sluggish though coil and switches are fine: replace Q77
- Which transistor drives the A/C select relay
Source: Repairing Williams System 11 Pinball 1986 to 1990, Deel 1, Clay Harrell (pinrepair.com)