Often baseball (pitch and bat style) pinball machines have problems with the
bat getting weak or not moving at all. This is often caused by a dirty
variable resistor. This is the large dial thing towards the inside front of
the machine, labeled something like 'bat strength, weaker <----> stronger'.
Try cleaning the backside of this with rubbing alcohol and turning the dial
back and forth, back and forth. If this doesn't solve the problem, you can
jumper over this component, eliminating it from the circuit. If the bat
doesn't move at all be sure to check the bat fuse which is usually mounted
right next to the dial. If the fuse keeps blowing then you'll need to
replace the bat solenoid, which is probably burned and shorted out.