How to check the magnetron in a microwave oven for serviceability with a multimeter and tester?

Microwave ovens are actively used in every home for cooking and heating food. However, the owners do not understand at all how exactly this equipment works. Therefore, when the device fails, repair difficulties arise. A magnetron for a microwave oven is a source of microwave waves, which, in fact, provide heating of food. Failure of this component is one of the most common types of microwave oven malfunctions. Now we will take a closer look at what a microwave magnetron consists of, how it works and methods for restoring this part.

What is a magnetron?

Appliances for heating food include one essential element. This is a powerful electron tube called a magnetron. With its help, microwaves are produced to influence water molecules in food. This process can be explained by the interaction of the magnetic field with the flow of electrons.

Without going into details of the power of microwave ovens, it should be noted that most of these devices have a power of 700-850 W, which makes it possible to boil a glass of water in just 2-3 minutes. It should also be taken into account when diagnosing that there are tunable and non-tunable devices, while in the former, a change in frequency characteristics can be observed up to 10%.

How does a magnetron work?

A magnetron is a vacuum tube that performs the functions of a diode and consists of several main parts:

• a cylindrical copper anode, which is divided into ten parts;
• in the center there is a cathode in which a filament is built in, and its main function is to create a flow of electrons;
• at the ends there are ring magnets necessary to create a magnetic field, which provides microwave radiation;
• a wire loop connected to the cathode, which is removed from the magnetron using a special emitting antenna and directed along a waveguide into the chamber; its main function is to collect radiation.

During operation, the magnetron heats up greatly, and therefore the case of this device is initially equipped with a special plate radiator and a blown fan. To protect this element from overheating, the power circuit has a thermal fuse.

Check Features

The capacitor is checked for serviceability using various methods. The main method is by desoldering it from the circuit. Sometimes you can check the functionality without soldering. But the results of the study will not be accurate - it is influenced by other components. To check the circuit, testers with tiny voltages on the probes are used. Low voltage prevents damage to other components of the board.

Regardless of the features of the models, all electrolytic capacitors have high power. When the test is performed, they are recharged. Its duration is only a few seconds. During the charging process, an increase in the resistance level is observed, with the movement of the tester needle or a change in the digital indicators in the electronic multimeter.

Polar capacitors

These electrolytic conductors are polarized. When connecting to the network, it is necessary to check the correct connection. We connect pluses with pluses, and minuses with minuses. Ignoring this rule leads to an explosion of the electrolyte.

Electrolyte can be solid or liquid. The capacitance of the elements is 0.1–100000 μF. The purpose of the elements is signal alignment and filtering. Marks “-” and “+” are marked on the body. The positive lead is longer. When the polarity is reversed, a breakdown of the dielectric occurs, as a result of which the electrolyte instantly evaporates and the housing ruptures. The dielectric is paper impregnated with electrolyte. Modern buildings are pressed in at the top and cut with a cross. During an explosion, not the whole thing disintegrates, but only the upper part. Taking into account the specially weakened elements, in the event of a malfunction, swelling of the upper part is visible.

Non-polar capacitors

It is easy to visually distinguish non-polar from polar - it will not have polarity markings on the body. Non-polar ones have a different dielectric material. Consists of ceramics or glass. The self-discharge current is much lower, given the higher dielectric resistance than paper. The higher the resistance of the dielectric partition, the lower the leakage current.

It is not at all necessary to observe polarity when connecting to the circuit. Sometimes such conductors are made very small and included in the circuit in large quantities.

The capacity of the parts is small - from microfarads to picofarads.

Possible faults

Like any other device or element in household appliances, the magnetron tends to fail. And a violation of the functionality of this part can be observed for the following reasons:

• burning of the protective cap, which can cause a spark during operation, in which case it is necessary to replace it with any whole one (usually they are all the same, so they are suitable for any magnetron);
• filament burnout;
• the process of depressurization of the magnetron, which can be observed as a result of overheating;
• the occurrence of a breakdown situation on a high-voltage diode;
• high voltage fuse blown;
• lack of contact in the thermal fuse;
• breakdown in a high-voltage capacitor.

In case of any malfunction, except for depressurization, it is possible to correct the situation at home without the help of specialists. If you do not have any experience in working with electrical appliances, it is better to contact a service center.

Microwave design

Although the design of a microwave oven contains a lot of elements, most of them do not play a special functional role. To repair this device, you only need to know the basic elements of the circuit that ensure its operation. Among them:

1. Magnetron.
2. Transformer.
3. High voltage fuse.
4. Rectifier diode.
5. Capacitor.
6. Control block.

Arrangement of elements in the microwave
It is easy to distinguish them, because the external design is not very complicated. The magnetron is always installed in the middle, aimed at the food heating unit. The transformer is located under it, representing a massive box with a protruding coil. The capacitor, diode and fuse are located to the right of it, and the control unit is often located near the input panel.

When the device is turned on, a voltage of 220 V is supplied to the transformer. Passing through the primary and secondary windings, a current of 2 kV already flows at the output of the element. Next, the negative half-wave goes to the diode, and the positive half-wave charges the capacitor, which again leads to a doubling of the voltage. After which the generation of microwaves begins using a magnetron. The magnetron power is controlled by the control unit.

Therefore, in the event of a breakdown, it is worth paying attention to these elements. They bear the greatest load, so the problem often arises in them.

When disassembling the microwave, be sure to unplug it.

How to check if the magnetron is working properly?

In fact, the magnetron is the main part for the normal operation of a microwave oven. And in the event of a serious breakdown, most people prefer to purchase a new device rather than repair the old one. But if the oven still fails, be sure to diagnose the magnetron of the microwave oven for serviceability in order to make sure that the breakdown is caused by a malfunction of this part.

The main signs of a magnetron failure are the appearance of smoke, sparks and sounds from the microwave.

If these signs are absent, you should conduct a general check of the microwave oven using a special tester.

General check

First of all, disconnect the microwave oven from the power supply. To do this, unplug the power cord from the outlet. After this, conduct a visual inspection of the internal compartment of the furnace, which will make it possible to detect melted walls and places that have burned or darkened as a result of operation.

Such visual diagnostics make it possible to detect a blown fuse. If there are no malfunctions, you should use a special measuring device. Hidden magnetron failure can be detected using a tester.

Checking with a tester

It is important to diagnose the part not connected to the microwave. The check is carried out in several stages:

1. Connecting the tester probe to the magnetron terminals. If the filament burns out, the tester will display infinity.
2. Inspection of the main printed circuit board, which contains diodes, resistors, varistors and other parts. In order to carry out the test, there is no need to unsolder each element, since ringing can be done directly on the board.
3. If the thermal fuse rings at room temperature, a signal should occur.
4. The high-voltage capacitor should only be checked for breakdown. If it is in normal, working condition, then it will show infinity. If the capacitor is faulty, then a resistance close to zero will be displayed.
5. Diagnostics of a high voltage diode. Due to the series connection of diodes in its design, it is not possible to inspect it. The internal resistance level is high enough to allow measurement. Therefore, you should make sure that there is no breakdown in this part. You can use a megger for this.

Disassembling a microwave oven yourself

If the above reasons are not confirmed, then you need to disassemble the device to troubleshoot.
Before doing this, be sure to turn off the oven from the network and wait a couple of minutes. Fuse

What should you look for when looking for breakdowns? There are several main elements that often fail:

1. Circuit breakers.
2. Capacitor.
3. Diode.
4. Transformer.
5. Magnetron.

Microwave capacitor photo

These elements are directly involved in the operation of the device and were mentioned earlier. First you need to check the serviceability of the fuses. Their breakdown is immediately visible, because when burned, the conductor inside is destroyed. If this does not happen, then you should look further.

For further checking, you need to take a multimeter, because externally it is extremely difficult to find a breakdown on the remaining parts. To check the capacitor, you need to switch the device to ohmmeter mode and then connect it to the part. If there is no resistance, the part must be replaced.

High voltage diode

It is impossible to check a high-voltage diode with a tester. It is recommended to replace it if other parts break, because often it also gets hit. It can be checked using a slightly different method - by connecting it to the network on the way to the light bulb. If the light is dim or blinking, then the part is working properly. If it lights up brightly or does not turn on at all, then the diode must be replaced.

Read also: What are screwdriver bits

Next, the transformer is checked.

Photo of microwave transformer

It is important to follow safety precautions, because

Photo of microwave magnetron

This element is able to hold a charge for a long time. It will take several minutes to discharge a working transformer, and much longer if the discharge resistor breaks down. It is worth discharging it on the body or not touching it at all if you have no experience working with such equipment.

Next, the transformer windings are checked. You need to remove the terminals and check the device terminals one by one with an ohmmeter. First, the primary winding is checked, for which the norm varies from 2 to 4.5 Ohms. For the secondary winding, the limits are 140 and 350 Ohms. It is also worth checking the filament winding by connecting the terminals leading to the magnetron to a multimeter. The norm here varies from 3.5 to 8 ohms.

All previous tests have failed, then the problem may lie in the magnetron.

To test the magnetron, simply connect the tester to its power terminals. The tester switches to ohmmeter mode. If the resistance is 2-3 Ohms, then this means the device is broken. The same situation occurs if the tester shows infinity. In both cases, the device must be replaced.

The listed elements are the most common culprits of microwave oven failure. However, device failure is often associated with other problems, such as problems with the electronic control unit, timer and other electronic parts. Here simple checks with a multimeter will not help; the help of a qualified technician is required. Although it is much easier to simply replace the part if you are sure it is broken.

Magnetron replacement

Repair of a broken magnetron is not carried out even in specially equipped workshops, so you will have to purchase a new part. Before removing the magnetron from the microwave oven, you should mark the connector contacts to avoid confusion in their connection when installing a new part. If the leads are connected incorrectly, the magnetron simply will not function.

In fact, you can replace the magnetron with a new one yourself. To do this, it is enough to be able to use a screwdriver and be able to ring diodes. Therefore, narrowly focused knowledge and skills are not required. If you cannot find a specific magnetron model for a specific microwave, you should use the most suitable analogue.

To do this, it is important to select the appropriate magnetron power, which should be either equal to or greater than that of the broken original. The fastenings and connector locations must also match.

The magnetron device itself is the same for all manufacturers, but their design may vary, so it is important to pay attention to the fit of the analogue to the waveguide, which should be tight. If the thermal paste on the thermal fuse is dried out, it should be replaced with fresh one when replacing the magnetron.

We are looking for a technical reason

If the microwave oven is inspected and you do not find anything preventing rotation, you will have to look for technical problems. Most likely, the microwave oven will need repairs, the complexity of which is again determined by the source of the breakdown.

It is logical to assume that the stoppage of movement is due to a malfunction of the torque mechanism. But the problem can be caused by even such a trifle as a burnt-out interior light bulb - this is what owners of older generation microwaves face. Look for problems that led to the stop in the following components and parts:

• Gear. A broken gearbox is one of the most common causes of a pallet stall. Replace it. If this does not help, you will need serious and expensive repairs - replacing the engine. Considering the cost of such repairs, it is cheaper to recycle the old device and buy a new one. This way you won’t have to spend money on repairs; you will purchase a new, more reliable and functional model from a reliable manufacturer.

• Clutch. This connecting mechanism, slipping on the shaft, can interfere with rotation. Try to strengthen it by eliminating slippage. Did not help? Then you need to change the clutch.
• Motor winding. If it is torn, professional intervention will be needed. The winding cannot be restored; it needs to be replaced. You can radically solve the problem - change the motor. You can find out about damage to the winding without disassembling the equipment - the smell of burnt varnish appears.
• Power circuit. To check the integrity of the power circuit, test the wiring with a tester. Did you find an open circuit? You just need to eliminate it.

Useful tips

Below are some tips to help extend the life of your microwave oven and the life of your magnetron:

1. If crackling or sparking noises occur during operation of the appliance, you must stop using the oven and find out the root cause. In any case, repairing a malfunction is cheaper than buying a new microwave oven. Most often, the culprit of such symptoms is the burnout of the magnetron protective cap.
2. Regularly monitor the condition of the mica pad, which is designed to protect the exit of the waveguide into the chamber. Fat and food crumbs often get into it, which leads to breakdown. If the cap malfunctions, the mica may be burnt, which becomes the main cause of magnetron failure. Therefore, it is important to keep the pad clean, since the fat that gets on it becomes electrically conductive under the influence of temperature. This causes sparks to appear in the oven chamber.
3. If the voltage is unstable, it is better to connect the microwave oven through a stabilizer. Due to minor drops and vibrations, some oven parts may fail. As the power drops, the wear of the magnetron cathode accelerates.
4. Remember that the main cause of failure may be not only the magnetron, but also other parts. Therefore, to begin with, it is important to check the voltage in the area where the furnace is connected to the electrical network, as well as the condition of the mica plate.

The magnetron is the main component of any microwave oven. And with proper care of the household appliance, as well as with timely detection of damage, it is possible to extend the service life of this device.

If the engine breaks down

The most unpleasant reason why a plate does not spin is a broken motor. As mentioned above, replacing the motor is an expensive pleasure, which not every owner of a microwave oven can decide on. It is necessary to first calculate the rationality of such a step. Often the malfunction is associated with a broken gearbox or poor-quality wiring. In any situation, the motor needs to be replaced.

To understand the causes of the malfunction, you need to know the engine structure. Let's take a closer look at the mechanisms that affect the operation of the motor:

Motor shaft. With its help, a rotational movement is produced. Shaft failure can be caused by careless handling or interference with its operation, for example:

• manual braking;
• touching the walls of the chamber with the dishes;
• increased load on the mechanism.

Important! After purchasing a microwave oven, be sure to read the instructions to know how to use it correctly and what loads it can withstand.

Motor housing and gearbox cover. Their job is to prevent water, food particles and foreign objects from getting inside the microwave.

Gearbox. Responsible for the functioning of the rotating element. Gearbox failure rarely occurs - it is a fairly wear-resistant mechanism. When the gears involved in rotation wear out, it breaks.

Attention! Today, microwave ovens use plastic analogues instead of metal gears, which does not contribute to the durability of the gearbox.

To find out the reasons for the breakdown, you need to disassemble the device. First remove the panel covering the engine. Then it is removed and unscrewed with a screwdriver and pliers. Often fat accumulates under the lid - it must be carefully removed without damaging the mechanism. You can use regular alcohol or a special composition. When the fat is removed, it is necessary to lubricate the important components of the motor and secure the housing.

What kind of motor is needed?

For a motor to work fully, it must have low speeds and high torque. It also requires high efficiency and energy efficiency. Microwave ovens use low-power synchronous motors (4 W), making 3-7 revolutions per minute. They can easily turn a plate on which several kilograms are placed.

To replace a broken motor or gearbox, you don’t need any special talents - follow the appropriate video instructions:

When replacing the motor , do not turn the shaft if you touch the power terminals - you may break the gearbox or get an electric shock . When choosing what to replace a broken part with, do not take cheap analogues - they are of poor quality and are unlikely to last long.