I've been trying to figure out why on my Williams Flash machine why certain coils aren't firing. When I use a voltmeter all of my drop target coils and ball reset coil appear to be shorted together. I am burning up a drive transistor to one of the drop targets which is solenoid #4 and Q21. Should all of these coils be connected in some way to one another? I'm thinking this is where my problem is but hoped someone could help me figure it out. All of the drop target coils were replaced by the previous owner. I know the ball reset diode is not shorted but haven't checked any others yet.

OK so first of all thanks everyone. The diode is shorted across the coil that has the driver transistor frying. Just wondering if this would cause the other coils not to fire. I did check the pre driver transistors and none of them seem to be shorted at any of their pins and seem to read the same resistance. I was going to replace the driver transistor and diode and see what happens and in the mean time order some of the pre driver transistors. This game does have a new motherboard by the way.