Which transistor drives the A/C select relay
The A/C select relay decides whether drivers Q22-Q25 and Q30-Q33 feed bank A or bank C. Before Big Guns the relay is on the power supply board and Q7 drives it; from Big Guns on it is on the auxiliary power driver board and Q8 drives it. The relay is 24 V DC, 10 A, DPDT. High Speed and Grand Lizard do not use it (it is fitted but idle; on High Speed Q7 drives a kickback).
Systems
Related tips
- How the System 11 A/C bank select works
- A/C select relay fails: welded contacts or cracked joints
- Later System 11 moved relay and diode boards to the backbox
- 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 output drives the bank select relay
- C-bank coil or flasher not working
- A-bank coil not working
Source: Repairing Williams System 11 Pinball 1986 to 1990, Deel 1, Clay Harrell (pinrepair.com)