Microwave was emitting a burning smell but operating normal. Next day it quit heating but everything else worked normal, no unusual sounds. Pulled it out and found the Thermostat on the side of the Magnetron burnt and seperated. My question is, what could cause this and what should I check for? I have parts ordered for what obviously is wrong, but what could have led to this failure? I would be happy to hear this could be the only problem due to age of the thermostat.

Thanks Gene. Would you suspect the Magnetron even if it was working in all modes, then suddenly quit? The Thermal fuse was burnt so badly, the spade connector from the transformer was burnt to the connector and the downstream spade connector was completely burnt off. The insulator over the thermal fuse was melted, yet there was no heat damage to the metal exterior of the Magnetron where the thermal fuse mounts directly to.