Maybe I'm wrong but I think I discovered a mistake in the Williams Driver Board Assembly Drawing for at least Firepower and Blackout (which I own).
As I was replacing resistors/diode/relay for my unresponsive flippers in my Blackout, I noticed resistor R20 is showing twice : once by Q9, and once by Q13 (flippers control).
R20 is a 68 ohms resistor but it's definitely not the right one for the flippers control. There, we should have the R26 10k Ohm. I removed mine and measured it at 10k ohm (I replaced it anyway)
No big deal as maybe only 5 people in the world had ever changed resistor R26 but in the idea of sharing knowledge, I thought this could be useful info
What I see on the Assembly Drawing :
what I think the drawing should show :