The microwave has become an indispensable assistant in the kitchen and in offices. It saves time when reheating ready meals and defrosting semi-finished products. We are so accustomed to the existence of a microwave oven that we immediately begin to panic if any difficulties arise in its operation. Let’s try to figure out what kind of malfunctions can occur in a working microwave, and what ways to fix this problem exist.

The device of the microwave oven and the principle of its operation

Before trying to find a breakdown on your own, you should study the device and understand how it works. A microwave oven consists of: a chamber, a door with a seal, a magnetron responsible for generating energy, an energy converter – a transformer, a diode, a capacitor, a fan. Auxiliary elements of the microwave are grill and tray lamps, fan and tray motors. Products in the microwave oven are heated by exposure to high-power electromagnetic radiation.

Microwave device

Microwave device

The waves penetrate the contents of the chamber and affect the molecules, which, as a result of such penetration, begin to move towards the lines of the electromagnetic field. The movement of molecules provides heating of products from the outside and from the inside.

Magnetron – a diode that provides the generation of electromagnetic waves when a stream of electrons interacts with a magnetic field. In the center of the copper anode in the form of a cylinder, there is a rod cathode with a channel filament, and it is this cathode that releases electrons. The standard power output by the magnetron is 800 watts.

Magnetron - diode

Due to the fact that the magnetron generates a lot of heat during operation, its case must be placed in a plate radiator, constantly blown by air coming from a fan. Also, for reasons of protection, the magnetron is supplied with a special thermal fuse, overheat warning.

Another important component of any microwave is fan. The fan blows the magnetron, the grill, the chamber itself, from which, thanks to the action of this device, air and water vapor come out. With the help of air ducts located inside the furnace, the air is circulated, which is received by the fan from the outside.

microwave fan

Every oven has shielded camera, protected by a metal housing that prevents the penetration of radiation to the outside. The metal mesh on the glass of the microwave oven door is also not accidental – it does not transmit 2450 Hz rays. The door itself should fit very clearly to the body, it is important to exclude any even the smallest distortion of it. A so-called standing wave of electromagnetic impulses is formed in a naturally formed gap that retains its geometric shape, it takes on a value equal to 0 exactly here, and this prevents radiation from penetrating beyond it.

Microwave control unit

Control block It is designed to maintain the set power and turn off the device after the set time has elapsed. These are the two main functional parameters.

On a note! In modern models, the functionality of the unit has expanded significantly, and now microwave ovens may have a built-in clock, a power indicator, standard cooking or defrosting programs, an end-of-work signal, and some other functions.

A detailed principle of operation, as well as a diagram of the device of a microwave oven, including an electrical circuit, are given in this article.

How to fix typical microwave oven failures

Some of the typical malfunctions and options for abnormal behavior of the microwave oven can be eliminated by the user on their own. However, it is worth noting that this will require some skills in using measuring equipment and elementary care when disassembling and assembling the furnace. Basic knowledge of the design of electrical circuits will not be superfluous. And, of course, all work should be carried out only when the furnace is turned off. That is, it must be physically de-energized by pulling the plug from the 220V socket.

Microwave won’t turn on

It is impossible to repair the power control unit without special skills. It is recommended to contact the nearest service for such work. But some checks can be done by the user himself.

  1. Socket being tested. You can simply turn on another electrical appliance in it. If there is no voltage, you need to eliminate this breakdown.
  2. The microwave power supply is being investigated. To do this, you will have to open the case of the device. There is a fuse on the board in special clips. It needs to be inspected and checked for conductivity. If the element burned out, you can try to replace it.

Important! This must be done using the same brand of fuse. It is strongly not recommended to install parts with a large operating current rating.

When there is power at the outlet, and the fuse has been checked or replaced, you can try heating a glass of water in the microwave. If it still does not work, then the problem will have to be fixed at the service center.

heat a glass in the microwave

There are failures in the execution of the specified mode

It happens that the microwave does not turn off after the end of the timer, does not start or stops working right during the heating cycle. This most often indicates malfunction of the door microswitches. There are several. For simple repairs at home, the door must be carefully disassembled, if necessary, clean the contact groups of the microswitches.

Another problem that causes failures when executing the specified mode can be caused by malfunctions in the power transformer power control relay. This item is not repairable. If, when the contacts are ringing, there are positions with incorrect operation, the relay is changed entirely.


The most difficult situation when failures cause malfunctions in the control unit. They are eliminated either in a service center or by completely replacing the module with a new one.

The device does not heat up well

When the voltage drops in the power supply, a slight heating of the microwave oven is normal. It is typical for houses in rural areas or in areas with an overloaded power system. Already at a voltage in the outlet of 205V, a sharp drop in the intensity of the magnetron radiation occurs.

But if the mains voltage is normal, you should test the power elements of the microwave power system. It is also worth remembering the time during which the microwave oven is operated. If it is measured over several years, and the decrease in heating intensity all this time has been gradual, then simply magnetron lamp burns out. This item has a finite life and must be replaced.

microwave repair

Microwave not heating

With the control panel running, starting timers and modes, the microwave does not heat only when malfunctions in the power supply system.

  1. Check the voltage on the primary winding of the power transformer of the magnetron. If it is missing, the control module needs to be repaired.
  2. If there is voltage on the primary winding, check all the key points of the radiation generation system. Namely, the performance of the transformer, the characteristics of capacities, diodes, magnetron.
  3. The transformer is tested by measuring the conductivity of the primary and secondary windings. If their resistance is close to zero, a short circuit has occurred between the turns. If to infinity – break.

Anyone who knows how to use a multimeter knows how to check the characteristics of capacitors and diodes. FROM magnetron testing everything is more difficult. Do a few checks.

The first relates to the lamp. If, when checking the resistance of its filament, the multimeter shows an extremely low value of the parameter, everything is fine with the element. Otherwise, inspect the filter coils, their fastening contacts.

If everything is in order there, the magnetron needs to be changed. The need for such an action will also be indicated by checking the passage capacities, when the resistance when touching one probe of the multimeter to the case and the other to the contact, the resistance is not close to infinity.


The appearance of sparks indicates a violation of the insulation of the working chamber. This means that the mica plate covering the magnetron window has burned out. Or the nozzle-lid that rotates the glass tray is broken. It may also be that the user is using the wrong cookware. Sparks on metal bowls, forks and spoons forgotten in the plate are normal. It is worth remembering that parts made of conductive alloys cannot be placed in the microwave.

forbidden dishes for microwave

Tray does not rotate

The pallet drive system is quite simple. If it doesn’t work, it could be jamming. This is checked manually by rotating the plate. There may also be a break in the contacts to the engine. The most difficult problem is the breakdown of the gearbox. It makes no sense to repair it, it’s cheaper to buy a new unit.

The device does not respond to control panel commands

If we are talking about a model with mechanical switches, they are all subject to mandatory cleaning, inspection, and replacement of faulty elements. In electronically controlled microwaves, no reaction means failure in the power management module.

Scoreboard not working

The control module is responsible for the operation of the display in the microwave. There is only one culprit.

The fuse blows when the door is closed

Such a problem indicates a short circuit in the control circuits. The reason is microswitches in the door. If one of them sticks, a short circuit may occur. Repair is quite simple: the door needs to be disassembled and all microswitches checked.

Thus, the list of possible malfunctions that can befall your microwave oven is quite extensive. You can deal with some breakdowns on your own and without much effort, and the failure of individual elements, the repair or replacement of which is associated with both risk and a certain complexity, requires the attention of professionals. A microwave oven can serve you for many years if you use it properly, following all the rules, and pay attention to the slightest malfunctions in the system in time.


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