Identify the controlling transistor for the kicker that is giving you trouble. Add a jumper wire to the metal tab of the transistor and have the other end isolated from any cabinet metal. Now play the game, when the kicker stops working try grounding your jumper wire to the cabinet ground wiring (braided cable, etc.) - does the kicker fire or not?

If it fires every time, then the problem is in the logic that controls the transistor. If it doesn't fire, then the problem is between the driver transistor and the coil connection.

Check the coils' lugs when it stops working - do both show roughly 48VDC relative to ground? If only one side does then you have a solder issue on the coil wiring or a broken coil wire to the lug. In rare cases the wire was not soldered well (if at all) to the lug, and it only works when it makes a pressure contact.

If both sides of the coil show power, then check the metal tab of the controlling transistor - it should show the same voltage as is present at the coil (all relative to the cabinet ground). If the voltage is missing here, then check the wiring and the Molex pin and the Molex connector pin for connection issues. The pin at the header on the Solenoid Driver
Board could have cracked solder connection (common on singel-sided PCBs) - so we resolder all the pins when we see those boards in games we repair/overhaul. Good practice.

Report back with your results!

John :-#)#
www.flippers.com