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Sunday 13 May 2018 at 07:03
It's the 2n4401 that's connected to the input of the transistor. In the case of Q17, it's Q16. They tend to be one off number-wise, but that's not 100%. On the driver board physically they're located right above the transistor, but below the resistors associated with it
Source: http://pinside.com/pinball/forum/topic/williams-black-knight-blowing-solenoid-fuse#post-4395196