I don't know how handy you are, but the mucrowave has its own fuse INSIDE the chassis. Many years ago, mine died, and I unscrewed the cover and found a $2.00 screw-in fuse had blown. I went to the hardware store, bought a replacement and closed it back up and it worked fine for years after.
If you are not comfortable doing that yourself (messing with the cover could possibly change the shielding), then don't try this at home.