In the manual it appears that each solenoid has TWO associated driver transistors. Is this correct or am I misreading the diagram? The target reset solenoid locked on last time I played my Black Knight, now the solenoid does not work. I'm assuming the driver transistor shorted, blew and needs to be replaced (along with possibly the solenoid), but the manual shows this solenoid as being controlled by transistor Q21 AND Q10. Why are there two? Also, it shows Q10 as being a "special" solenoid.

Lastly, do the pre-driver transistors have an ID number or are they just considered "Q21's pre-driver transistor"? And the pre-drivers for System 7 are 2N4401, correct?

Thank you for the quick response !

So I replaced the driver (and pre-driver) transistors for this solenoid and it still didnt work. I checked the solenoid after and realized that it is fried. The plastic housing is melted. I know I should have checked the solenoid first but I did not. That being said, is there a good chance that the dead solenoid could have destroyed the brand new transistors I just placed? I did turn the machine on and the game tried to reset the drop targets, could this have blown the transistors since the solenoid is probably shorted? I will have to wait a week or so for the new solenoid to ship.