Hello, my microwave starts and runs, but makes a loud humming noise and will not heat. I think it is the Diod. it reads 4.9 both ways on my ohm meter. I know it should only read one way, but I thought if it was bad it would read open in one direction. Do you think my diod is bad.
Answer Hello George. You most likely have a "high voltage" side malfunction. Transformer, diode, magnetron, Capacitor. You will need to be extremely careful if you decide to test the components with a multi meter, Very high residual voltage is present, so make sure you remove power to the microwave and short across the terminals on the capacitor. The magnetron should have a reading of less than 1 ohm resistance across the two terminals, and an "open" circuit between each terminal and chassis ground. The diode/rectifier should have a resistance reading in one direction only, no resistance, or resistance in both directions indicate a faulty diode. The primary winding on the trans former should read approximately 450 Ohms resistance, the secondary winding should read 80 ohms resistance, and the filament transformer should read 100 ohms resistance. If all the readings are proper and in range, replace the magnetron.
What is involved in changing the magnetron bulb and the diode? Do l have to remove the microwave from the wall?
Answer Hello John. Yes, you will need to remove the microwave from the wall to access and replace the parts. You will disconnect the power and remove the outer cover off the unit. The be careful and discharge the capacitor on the unit. Now it is safe to remove the magnetron and diode from the unit and install the new parts. Make sure you discharge the capacitor first.