I determined that a capacitor was bad. The original was a .74uf 2500 vac capacitor. My local parts supplier had a .80uf 2100 vac capacitor that they seemed confident would be an acceptable replacement. I replaced the capacitor and microwave appears to be working fine now. My concern is will changing the size of the capacitor adversely affect the microwave ie. cause any damage to the magnetron, etc.

I assume that the one I installed would be considered close enough? Thank you for replying.