Spacemaker JVM1660SB008: No Heating Loud Humming Noise

The lights, turntable works on the microwave - but there is NO heating!!! In addition it produces a loud humming noise.

Could anyone please suggest troubleshooting tips and relevant part numbers for replacement (How do I isolate between a HV Diode, a Capacitor and Magnetron problems?)

Thanks for your help.
Doppan

Sci.Electronics.Repair FAQ: Notes on the Troubleshooting and Repair of Microwave Ovens