How Microwaves Work

On this page, I will explain how microwaves work. Understanding how an appliance works can help do-it-yourselfers repair the appliance more efficiently. You can use this page in conjunction with my microwave repair guide to help you better understand how your microwave works, so you can make repairs yourself. By repairing your microwave yourself, you can save money from expensive repair bills.

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Microwave repair can be dangerous! You must unplug the microwave before attempting to repair it because they use very high voltage on certain internal parts. After the microwave is unplugged you must also discharge the capacitor before servicing because the high voltage that the microwave operates on is stored in the capacitor. To manually discharge the capacitor, place an insulted handle screwdriver between the diode connection of the capacitor and ground. It should discharge itself but always discharge it manually!

Smart Board

The smart board, or the main board, is like the brains of the microwave. This is where everything is controlled. The function of the smart board is to set the time, power level, control the cooking time and control all of the automatic controls, such as the popcorn and defrost. Basically, the smart board distributes power throughout the microwave as needed or desired by the user. Smart Boards can be purchased at


When the microwave enters the cooking mode, the smart board sends power to the transformer. The transformer transforms 120-volts from your house wiring to around 5000-volts. This is done because the magnetron tube operates on this high-voltage. Transformers can be purchased at


The power that enters your house flows one way for 1/60 of a second and then the other way for 1/60 of a second. The magnetron tube of a microwave uses a direct current that only flows one way. The diode is a device that only allows the current to flow one-way converting alternating current to direct current. Diodes can be purchased at


A capacitor is a device that stores electricity much like a battery but can be charged and discharged instantly. As stated above, the power that enters your house flows one way for 1/60 of a second and then the other way for 1/60 of a second and the diode only allows the current to flow one way. This means the current will only flow half of the time. During the time that current is flowing, the magnetron tube will receive power from this current flow while at the same time charging the capacitor. Once the current flow stops, the magnetron tube will receive power from the capacitor. Basically, the capacitor provides a more steady power flow. Capacitors can be purchased at

Magnetron Tube

The magnetron is at the heart of how microwaves work, they are what causes the heat to cook your food. The magnetron tube produces radio waves that excite the water and fat molecules inside the food causing friction. The friction will cause the food to heat up almost like rubbing your hands together really fast.This is the most fundamental part of how microwaves work. Magnetron tubes can be purchased at

Door switches

The door switches will stop this process the instant the door is opened. Most microwaves have three door switches so that if one fails there are still two more to ensure that the cooking stops immediately once the door is opened. Door switches can be purchased at

Power level

The power level determines what percentage of time during the cooking cycle that the magnetron tube will be energized. For example, on power level 10, the magnetron tube will be energized 100% of the cooking cycle but when the power level is set to 5, the magnetron tube will only be energized for 50% of the cooking cycle. In normal time cook the power level will automatically be set to 10 but can be changed manually. In defrost the power level will be set somewhere around 3. The smart board controls all this.

To sum it all up, the smart board sends voltage to the transformer. The transformer steps-up the voltage to a much higher voltage. Then the diode converts alternating current to direct current. The capacitor provides a more steady current flow. Finally, the magnetron tube produces radio waves to cook the food. I hope this page helped you better understand how microwaves work so that you can make repairs to it yourself.

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