Microwave is making a loud humming sound when cooking. It does not heat. I replaced the HV diode and it still made the loud buzzing sound. I pulled the diode out and it reads 17 ohms both directions. I have checked the magnetron, it reads less than one ohm reading both terminals. Reads open to each terminal to ground. The capacitor check good. Reads ohms going up one way then descends when leads are reversed? I have disconnected the turntable, same thing. I have disconnects the stirrer motor, same thing. Thermostats check ok as well.
Can anyone help? Thanks!

Tim