Keith,

I'm going to go ahead and include my email response here. One thing I forgot to ask you - did you hear any loud popping sound when the microwave stopped heating? If you did, the rectifier (diode) is bad. Otherwise, read on:

Usually, when there is a strong electrical burnt odor coming from inside the microwave (inside the control panel to be more precise) it indicates that the high voltage transformer is bad. Depending on how long the transformer coil has been on and burning you may or may not visually see the damage on the coil.