Quoted from vikingerik:There's two different switches - one registers the drop target going down, the other registers the ball in the skull. It sounds like the latter (what I'd call the VUK switch) is working, since he can start multiball without any problems, and the drop target raises after a lock in the skull during multiballs. It sounds like the drop-target-down switch is the one that's not working; that's not needed to start multiball or score a jackpot, but is needed to re-raise the drop target when it should stay up while a ball is locked in the skull.
Check that the VUK still has the popper cap/cup on it. Often they are missing. Check it against the manual.
The VUK should fire the ball immediately or a soon as a ball rests on it.
With the game powered up, it will fire the ball even if a game isnt started if you drop a ball onto it.
If its unreliable, the forked switch contacts may need cleaning or adjusting. They are gold, dont file them, use metal polish on a q-tip if they are black.
The drop target assembly might just need inspection, cleaning and lubrication. Often thay are not assembled correctly and need parts. They also get worn and are not reliable.
If something isnt right, remove both assemblies from the game and inspect them for proper operation.
Adding molex connectors to the wires makes maintenance a breeze.
Generally the mechs just need cleaning and new coil sleeves and coil stops if they look worn out.
Switches sometimes get loose and need adjusting.
Switches do get old and unreliable, but they are inexpensive to replace.