Plastic burning smell

Microwave Repair
1

I have a Frigidaire FGMV174KFB over the range microwave. The problem is a loud buzzing sound along with a plastic burning smell when it runs. I don’t know if it heats or not, because I am afraid something might catch fire. Any idea what I need to look at would be greatly appreciated. :confused:

Could it be the high voltage diode?

Thanks