take the switch out of the circuit
Do you have a jumper lead (AKA test lead) with alligator clips on each end? Very handy for testing stuff, trial hookups, etc.
I would unplug the power cable. then use a jumper lead to connect the two switch contacts together (where the wires connect to the switch). Then plug the power cable back in.
If it works, then you need to replace your switch. If it pops a fuse (or one of your house fuses or breakers), then you have a problem in your power supply.
DO NOT poke around in there with the power cable plugged in!