Why the lights and timers work but the unit won't turn on.

"Make sure your life insurance is paid up and there is no suicide clause in it. Because working on one of these might be considered suicide. I won't touch the inside of one like this.

Cause 1

Diode

The diode converts the A/C power output of the transformer to D/C, doubling the voltage to nearly 5,000 volts. This high voltage powers the magnetron to heat the food. If the diode burns out, the magnetron won’t receive enough voltage to operate, preventing the microwave from heating. When the diode fails, it is often visibly burned out. Inspect the diode and if the diode is burned out, replace it. If inspecting the diode proves inconclusive, test it with a multimeter that uses a 9-volt battery or put a 9-volt battery in series with the diode. When the leads are reversed, the diode should only have continuity in one direction. (Warning: The microwave oven can store a lethal amount of electricity in its high voltage capacitor, even after the microwave oven has been unplugged. Due to the high running voltage and the potential for electric shock, it is extremely dangerous to replace the electronic components in a microwave. Only a licensed technician should replace the diode.)

Cause 2

Door Switch

Most microwaves have three or four door switches. When the microwave door closes, the door switches actuate in sequence to ensure that the door is closed properly. If any of the door switches fails, the microwave will not start or heat. To determine if any of the door switches are defective, use a multimeter to test each of the switches for continuity. If any of the door switches does not have continuity, replace it. (Caution: The microwave oven can store thousands of volts of electricity in its high voltage capacitor, even after the microwave oven has been unplugged. Due to the potential for electric shock, it is extremely dangerous to replace the electronic components in a microwave. Only a licensed technician should replace a door switch.)

Cause 3

Magnetron

The magnetron uses high voltage, high current DC power to generate the microwave frequency that cooks the food. If the magnetron burns out, the microwave won’t heat. The magnetron is not repairable—if the magnetron is burned out, you must replace it. (Warning: The microwave oven can store a lethal amount of electricity in its high voltage capacitor, even after the microwave oven has been unplugged. Due to the high running voltage and the potential for electric shock, it is extremely dangerous to replace the electronic components in a microwave. Only a licensed technician should replace the magnetron.)"

"I have two of these microwaves. They both had a failed relay on the control board. It is labeled Lamp Relay (RY1) on the schematic. It's inexpensive and available from electronics suppliers, such as Mouser or DigiKey. When it fails, the timer still works, but the light, fan and turntable will not work. The failure also disables the magnetron.

Note that both of the relays on the control board switch the ""neutral"" side of the line, but that's no guarantee that they don't have 120V on them due to some other failure, since the neutral is floating. The magnetron is controlled by these relays, plus two of the three door switches.

Never stick ANYTHING inside an open microwave cabinet without first grounding the terminals of the high voltage capacitor with a screwdriver blade. Short the terminal with the diode on it directly to the chassis ground. I then short both terminals together, just in case the transformer primary has an open circuit. You can test the filament in the magnetron and the windings of the transformer with an ohmmeter. You must disconnect the wires to do so."

Our Viking microwave VMOS200 just suddenly quit. I was just using it and it wouldn't restart. The light came on and the timer would count down but carousel wouldn't rotate and it wouldn't start. Watched a YouTube video and found the exact situation and the repair was the micro door switch. There are four inside this model and 3 are normally open and one normally closed. Using an ohmmeter to check them to see which was faulty. All functioned normally except one which was intermittent and wouldn't work in the normally open position but would work with a slight pressure on the door open button. I replace the switch and it worked perfect. https://www.youtube.com/watch?v=_CtGVScF...

"Hello rfollowell51,

I have exact same issue with my VMOS200; can you share the part # that you changed?

Thanks

AJ"

https://smile.amazon.com/gp/product/B074... I purchased this pack of 2 . exact replacement.

'I have a Samsung microwave and I brought it brand new a year ago. now its not working it was working perfectly yesterday. And now this morning it not. when I plug it up the clock light and the inside light on the inside will not come on and when I open the microwave door and close the door the clock will blank on then off then thats how it will stay, is off. Can someone please tell me whats the issue sounds like I hate to throw this new microwave away I really do I'm so mad.... danggggg....