For those of you with the Bally "Special Force" pinball (6803 hardware), I bet you noticed the Solenoid Expander Board AS-2518-66 is not shown or listed in the manual. If you need the schematic and parts list for it, I found those in the Eight Ball Deluxe manual. The board schematic is in the schematics section of the manual and the physical board layout and parts list is in the parts section.
In Special Force, Q25 (2N5060) on the control (CPU) board turns on the lamp next to the expander board which also turns on the relay on the expander board. Remember, this bulb has to work or else the expander board can't turn on the relay. So if the 555 bulb is burned out or missing, there's not going to be enough of a load for Q25 to latch on the MOC3011 optocoupler driver that energizes the relay.