The fuse for this model is on the filter board on top of the internal cooling fan frame.
You can find helpful exploded view diagrams and order parts by entering your full model number from the tag on the oven (JMC8130DDS) here.
http://www.appliancepartspros.com/If the fuse tests good, then the oven cavity thermostat, magnetron thermostat, and control circuit board (
http://031d26d.namesecurehost.com/mwd/ ) are other parts that can make the oven dead.
Accessing some components (especially the oven cavity thermostat) for testing and possible replacement will require you to remove the oven from the wall and take off the outer cover.
If so, the installation instructions are very handy, and it's best to have two people since the microwave can be heavy and awkward.
You can download Jenn-Air owner's manuals and installation instructions here.
http://www.whirlpool.com/owner_centerHope it helped...