How to Test the Magnetron in a Microwave Oven

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You should have an appliance tech look at your magnetron than do it yourself.
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A microwave oven, also known as a microwave, is a handy appliance because it can heat and cook a variety of foods by using electromagnetic radiation in the microwave frequency range. The purpose of the microwave magnetron is to generate energy for the microwave. Although you can test the microwave magnetron for bad microwave capacitor symptoms, a microwave oven can give you an electric shock even when it's unplugged. That's why it's highly recommended to hire an appliance repair technician when trying to do any microwave oven repairs.


Background on Microwave Magnetron

According to Edison Tech Center, the cavity magnetron is the central part of a microwave. The concept of the magnetron was invented in the '30s by Dr. Albert W. Hull in Schenectady, New York. The magnetron operates as an oscillator, which is a device that generates oscillatory electric currents or voltages by nonmechanical means.


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In the magnetron, electrons emit from a hot cathode (the negatively charged electrode by which electrons enter an electrical device) and spin past cavities that generate microwave energy. The magnetron basically acts as a high powered vacuum tube.

How it Works

Microwave ovens are one of the most convenient methods when it comes to electric cooking. According to Edison Tech Center, the microwave oven uses the magnetron to generate microwave energy. The microwave energy travels through something called a waveguide and is then distributed into a metal cavity. Your food is cooked in this metal cavity.


The waves are absorbed by the food, and they excite the water molecules that are in the food. Heat transfers throughout the food, and that is how it is cooked or warmed up. Although there are many reliable electric cooking methods, compared to a regular oven, the microwave oven operates so much faster.

In microwave ovens, the energy is able to heat the food from the inside. But in regular ovens, the heat comes from the outside and slowly heats the food from the outside to the inside.


Before Running Any Tests

Before you run a test, you must make sure that your microwave is unplugged. According to Easy Appliance Parts, you also need to discharge the capacitor so you don't damage your microwave and tools as well as injure yourself. If you're not sure what the capacitor is, it's where a lot of electricity is stored.


Even if your microwave is unplugged, electricity is still running through here. That's why you must do the microwave capacitor discharge test before examining the microwave magnetron.

Discharging the Capacitor

To release the capacitor, you have to create a short circuit between each of the two capacitor terminals and the terminal and the chassis. According to Easy Appliance Parts, the chassis is the bare metal surface of the capacitor. When your microwave is unplugged, you're going to touch the end of an insulated screwdriver to one capacitor terminal.



Then you need to slide the screwdriver forward until it reaches the other terminal. When the screwdriver reaches the other side, hold it there for a couple of seconds. If you hear a loud pop, everything is OK. You're going to do this a couple of times until you create a short circuit.

According to D & F Liquidators, a short circuit is when there is a low resistance connection between two conductors. These two conductors supply electrical power to a circuit.


Testing a Microwave Magnetron

Easy Appliance Parts recommends two tests you can conduct to figure out microwave magnetron issues. For the first test, you need to locate where your microwave magnetron is and label the wires that are attached to it. Labeling these wires will help you if you need to replace a wire. After you mark the wires, you're going to set your ohmmeter to the lowest resistance scale.


An ohmmeter is an instrument that measures electrical resistance. Using the ohmmeter, you're going to place it between the magnetron's terminals. To do this, you're going to touch each probe to one terminal each. If everything is working correctly, the ohmmeter should read less than 1 ohm.

Second Magnetron Test

For the second test, set the ohmmeter to the highest resistance scale. Then you're going to touch one of the meter's probes to the magnetron terminal. Also, touch the other probe to the metal magnetron housing.


Make sure that you do not touch the two probes together. If the two probes touch, you will get an inaccurate reading, and you won't know if the magnetron is working or not. When running this test, it should have a reading of infinity, which means the circuit is open.

Another Magnetron Testing Method

In addition to those two tests, you can also run a temperature test to see if the magnetron is weak. According to Microwave Specialties, first, you need to make sure the unit is plugged in. Then you're going to fill up a beaker, container or cup with 1 cup of tap water. Test the temperature of the water to make sure it is approximately 70 degrees Fahrenheit.



Next, place the beaker, cup or container in the center of the microwave until the water is boiling. Depending on which model you have, it should take no more than 2 minutes for the water to come to a boil. The temperature should measure to 142 degrees Fahrenheit. If your water tests lower than 142 degrees Fahrenheit, then your magnetron is not functioning correctly, and you need to contact a repair technician.

Replacing a Microwave Magnetron

During either test, if you notice that the microwave magnetron isn't working, you're going to have to replace it. According to Easy Appliance Parts, it is highly recommended that a certified and experienced appliance repair technician replaces the magnetron. It's very dangerous for the average individual not only to test the microwave magnetron but also to try and replace the magnetron.

Even with clear instructions, if you're not adequately equipped to operate a microwave repair job, you can get a severe electrical shock. A certified and experienced repair technician will have the proper knowledge and tools to test and replace the microwave magnetron. They can also inspect to see if you have any other issues when they conduct a microwave oven inspection.



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