Loud Buzzing Noise?

To Whom It May Concern:
My Whirlpool GH7145XFQ overhead microwave makes a loud buzzing sound when turned on. It worked yesterday. I recently cleaned the grease screens and filters on the underside of the unit, but don't think my reinstallation of the screens had anything to do with it. Can you tell me if it's the capacitor or diode, or some such. Can I fix it?

Thanks,

Katman