It is best not to try to assemble the high voltage fuse with your own hands or remove it from the electronic board. This practice is extremely dangerous for people. The microwave oven may stop working and there is a high risk of fire and electric shock.
Before you start talking about repairing a fan that cools a magnetron, grills or an illuminating lamp in a microwave oven chamber, you should also pay attention to the protective relay. Their task is to turn off all operating systems at the moment when the chamber door is in the open position. Two relays usually break the power supply circuit. And one relay will be controlled by the functionality of the second. The work is carried out as follows:
The fuse is not meant to be on top of the magnetron or inside the case, but on the board. To fix a microwave oven with your own hands, you should check the operation of the protective relay. Without this functionality, access to the power supply to the magnetron is practically impossible. The task of the power fuse is to take into account the movement of current in the magnetron. In the event of a dangerous situation, the protective element burns out, the generator breakdown is excluded. A similar situation occurs when the microwave oven is idle or there is some kind of metal thing in its chamber.
The reason that the microwave works, but does not heat the food, may be not only a serious breakdown, but also a minor malfunction, in which any housewife can restore the device to work. As a rule, the reasons for entering microwave ovens are commonplace and the same even for models from different manufacturers. It is stated below in which cases the microwave oven can be repaired with your own hands, and in which cases only the master can return the oven to work after replacing the damaged parts.
Often a situation arises when the owners of the microwave oven, which does not heat the food, in vain dump the blame for the cold breakfast on the manufacturer. In fact, the reasons for the unsatisfactory performance may be completely unrelated to the state of the internal elements of the device.
Before proceeding with the disassembly of the microwave oven and search for faulty modules, be sure to read the instructions and user manual. Often in it you can find an answer or hints on how to make repairs with your own hands.
The first step in checking the internal circuitry is to measure the voltage. As mentioned above, the operation of a magnetron emitting microwave radiation may depend on this indicator. The operating voltage range is indicated in the technical documentation of the furnace.
If everything is in order with the voltage, you should check the operation of the door. With a small switch on the side, it signals the magnetron to turn on after closing. It is checked using an ohmmeter.
A further check of the oven's serviceability is carried out in the functional block, for access to which it is required to unscrew the back wall. After that, you must first check the high-voltage fuse. Visually - the integrity of the filaments and glass casing, and hardware - for resistance. One way or another, the repair here is very simple and easy to do on your own - you need to replace the part with a new one. Going to the market or store for a replacement, it is better to take the broken element with you in order to accurately select the model. The use of so-called bugs is highly undesirable - they are fire hazardous, and the fuse is not so expensive to risk.
This element of the internal structure of the microwave oven consists of two parts - a capacitor and a diode. The serviceability of the first can be checked with an ohmmeter, despite the fact that it is intended for alternating current networks. If the tester needle deviates and goes to infinity, everything is fine - the capacitor takes a weak charge. If the arrow remained stationary, this would indicate a break in contact. And if the tester immediately signals a small resistance, there is a breakdown. Be sure to discharge the capacitor before diagnosing. Such a device is inexpensive, so it is better to replace it immediately.
By the way, it is the damage to the capacitor that often becomes the reason why the stove buzzes when it turns on, but it does not heat well. In such a situation, the device may emit extraneous sounds and buzz.
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To check the capacitors of an electromagnetic lamp, you must first discharge them using an indicator screwdriver (short-circuit the leads in turn). The reason for the failure of this element is the short circuit of the capacitor leads to the case. To check, an ohmmeter is taken, one probe of which is installed on the metal case, and the other on the capacitance terminal. If there is no resistance, the part must be replaced. The same will have to be done if the resistance between the contacts does not correspond to the standard of 0.1 ohm.
Here, the tester checks the primary winding of the transformer. The voltage on it should be equal to 220V. For test heating, a dish or glass of water must be placed in the chamber.
The magnetron is a key element in a microwave oven. Repair specialists say that it is he who often becomes the reason why the microwave oven has become weak or has completely stopped heating food. When switched on, the magnetron emits electromagnetic waves with a frequency of 0.5 to 10 GHz into the microwave chamber. To put it simply, under their influence, the hydrogen atoms in the food begin to rotate, resulting in heating.
However, it is too early to draw hasty conclusions - the electromagnetic lamp itself is not always the cause of the malfunction.In many microwave ovens (even such trusted brands as Samsung, Daewoo, LG, Indesit), the magnetron stops turning on due to the loss of reliable contact between the power terminals and capacitors or the soldering of the contacts of the induction coils. In such a situation, repairs can be done without problems with your own hands.
If the microwave turns on but does not heat up, the filament installed in the magnetron may have broken. To check for this fault, you need to measure the resistance on the thread. If everything is normal, then the arrow of the device is at the level of 2-3 ohms, if it is broken, it goes to infinity.
Please note that the radiator and the metal housing of the electromagnetic lamp, after it is turned on, heats up to at least 150˚C. If you turned it on before to check the transformer winding, wait until the device has completely cooled down.
If, after all the steps described, the reason why the microwave oven turns on, but heats up weakly, is not found, the matter is a breakdown of the magnetron. In this case, it is better not to try to figure out the structure of this element on your own. It will take a very long time, and do-it-yourself repairs are unlikely to be effective. The easiest way to fix the problem is to replace it.
To buy a suitable device, you need to write down all the technical characteristics (for most furnaces they are located on the back panel) of the device and the magnetron: power, voltage and current of the filament, cathode voltage and anode current; and contact a service workshop with this information. Self-assembly of the magnetron is permissible, however, it is better not to save money and, for reliability, give this work to the master.
The reason that the microwave oven starts to weakly heat the food or stops doing it altogether is almost always the deterioration of one or another functional element. Of course, during the warranty period, you need to use the services of a service center. But in order for the device to work for a long time even after the expiration of the warranty, and not to have to do it yourself in order to save money, you need to avoid actions that reduce the service life.
It is better not to use metal utensils and generally avoid getting metal objects (forks, spoons, etc.) inside the oven. In order for the food to warm up during the operation of the microwave, and the dishes themselves remain cold, you need to avoid materials such as: crystal of different thicknesses and with the presence of different thicknesses, porcelain and glass with drawings of gold paint, disposable plastic dishes, ceramics without protective glaze, aluminum molds for baking.
Do not turn on the device idle - without food or food.
It is also undesirable to heat liquids and raw eggs in containers that "explode" when heated.
Failure of the touch panel is also a frequent malfunction, so it is advisable not to press on it with undue zeal and not get dirty. In many furnaces of well-known manufacturers, a breakdown of the touch panel is indicated on the display with a service code, for example SE (each manufacturer uses a different designation).
To avoid problems with microwave oven repair, you need to pay attention to devices made by reputable manufacturers. No matter how much these models cost in comparison with their Chinese counterparts, the build quality and materials used will pay off in the future. It is difficult to repair a cheap "nameless" device with your own hands for the reason that it is not easy to find the necessary parts for it, and the technical documentation does not always correspond to reality. And the masters who are faced with such a device can ask for a lot of money for repairs, since this will also be problematic for them.
We bring to your attention another article to help the home master. It will focus on the repair of microwave ovens from Samsung, LG, Panasonic and other popular brands. In the introductory part, we will briefly talk about the principle of operation and design features of microwaves. After that, we will give a list of typical malfunctions, an algorithm for diagnosing a breakdown and ways to solve the problem.As practice shows, in about 80% of cases of microwave failure, it can be restored by the efforts of a home craftsman.
We are so accustomed to microwave ovens that the failure of this kitchen appliance creates a lot of inconvenience. With its repair in the workshop, difficulties also arise, primarily related to transportation. Naturally, this raises the question of the possibility of repair on their own. In our article, we will provide a list of typical malfunctions and tell you about how to fix them. Before starting the repair of microwave ovens (Samsung, LG, Panasonic, etc.), we recommend that you familiarize yourself with their principle of operation and design features, this information will not be superfluous.
We will consider this issue superficially so as not to get away from the main topic. The information will be simplified as much as possible, since not all home craftsmen have a deep knowledge of electrical engineering. Let's start with a description and purpose of the main structural elements, they are presented below in the figure.
Legend:
Door latches serve both for fixing the latter and for the system of blocking work in the open position.
A rotating tray on which the dielectric cookware is placed.
Separator equipped with rollers that drives the pallet.
The drive that rotates the separator.
Backlight lamp, turns on depending on the operating mode.
Ventilation (usually forced).
Magnetron - a microwave generator, in fact, is the main structural element. You can find out how it works and how it works by reading an article on our website dedicated to this issue.
Waveguide, provides the movement of microwave waves to the microwave chamber. It is a rectangular hollow metal tube.
High voltage diode.
Capacitor.
Waveguide power supply transformer and control circuits.
Control block.
We will not give a complete schematic diagram of the device, since they can be very different in different models of microwave ovens. In our case, the supply circuit of the magnetron will suffice. As a rule, it has a typical structure.
Let us briefly describe the principle of operation of the above circuit. Power to the primary winding of the transformer (I) comes from an external control circuit that regulates the power and duration of microwave radiation. One of the secondary windings (II) supplies voltage to the magnetron filament. Winding II is made of 2-4 turns of a thick wire, since the current in the heating circuit can reach 10.0 A at a voltage of about 3 volts.
Another secondary winding (III), which supplies a high voltage level (up to 3.0 kV), is called anode winding. As can be seen from the figure, in this circuit, a rectifier and a voltage multiplier are built on the basis of a high-voltage diode (VD1) and a capacitor (C1). In this case, VD1 is turned on so that the opening occurs with a positive half-cycle, as a result, the capacitor begins to charge. When the negative half-cycle begins, the diode VD1 closes and the voltage is supplied to the magnetron M1 together with the charge accumulated on the capacitor. This leads to a doubling of the voltage and the formation of an electric field of the required intensity in the magnetron.
Resistance R1 in this case is necessary for C1 discharge. Typically, this resistor is located in the capacitor case. As for VD2, it provides protection in the event of an increase in voltage across the capacitor C1 or the occurrence of a short circuit in the magnetron M1.
Before proceeding with the repair, it is necessary to collect as much information as possible about the failed device. Ideally, this is a model-specific service manual. In this document, the manufacturer provides all the necessary data, starting from the assembly drawing (exploded view, literally from the English explosion-diagram) and ending with the troubleshooting algorithm.
Unfortunately, manufacturers are in no hurry to share this information, distributing it only among the networks of certified service centers. If you manage to find the technical documentation for the repair, be prepared for it to be in English.
If the documentation could not be found, and this will happen in most cases, do not worry, typical microwave oven malfunctions can be determined without a schematic diagram. It is enough to know what the main elements look like and where they can be located. A photo of the microwave oven with the cover removed will help you with this.
The intuitiveness of the process in most cases allows you to remove the casing and get to the main structural elements without an assembly drawing. But in this case it is necessary to remember the sequence of actions and try not to leave “unnecessary” parts after the reassembly.
In most cases, you can get by with a Phillips screwdriver and a multimeter. In some cases, you may also need a soldering iron. Accordingly, spare parts will also be needed, which ones will be clear after diagnostics.
As we promised, here is a list of common faults:
No response to the power button.
The device does not turn off after working out the mode.
Weak heating.
No heating.
Sparking is observed.
The pallet does not rotate.
No response to the control panel.
When turned on, the scoreboard does not work.
The fuse blows when the door is closed.
Before considering in detail the elimination of the listed malfunctions, we consider it necessary to warn that before diagnostics and repairs, it is necessary to physically disconnect the device from the power supply, that is, pull the plug from the outlet.
In this case, diagnostics and repairs should be subject to the following algorithm of actions:
We check the presence of voltage in the power supply. If it is not there, we solve the problem with the power supply, otherwise go to the next step.
We check the power supply unit of the control module. We start with the fuse. If it is burnt out, we will replace it. After that, we turn on the device and try to heat, for example, a glass of water. If everything works, the repair is complete. If the fuse blows, the problem is in the control module, it should be repaired or replaced.
In order to independently repair the control module, you must have certain skills in radio electronics; without them, it is not recommended to start self-repairing the control module.
In most cases, this problem indicates a faulty door position microswitch. To eliminate the problem, we find, check and, if necessary, replace the switch.
If the microswitches are OK, the problem may be with the relay supplying voltage to the power transformer in the magnetron supply circuit. We "call" the relay contacts with a multimeter, if they are "stuck", we change the electrical switch to a new one.
When no problems are found with the relay, it means that the malfunction is associated with the control unit, we change or repair it.
Most often, this malfunction is associated with a voltage drop in the household power supply. If it falls below 205.0-210.0 V, a sharp decrease in the intensity of the microwave flow occurs. This problem is typical for private houses in rural areas, where power grid overvoltage occurs regularly, and, as a result, voltage drops.
If the multimeter shows the permissible voltage level of the household network, then the power circuit of the magnetron should be checked, as we will describe how to do this in the next section.
When the diagnostics of the magnetron circuit did not give results, then everything indicates a problem with the control module.
Such a malfunction clearly indicates a malfunction in the magnetron power supply circuit. Diagnostics is performed as follows:
Important! The magnetron must be changed to the same type. This is due to the fact that the parameters of the high-voltage transformer and the control circuit are calculated based on the specific model of the microwave generator.
Such a malfunction can be caused by the following reasons:
Burnout of the mica plate, which insulates the waveguide from splashes and food pieces ... The plate is located inside the chamber on the side of the magnetron. The condition is determined visually. If the problem is with the plate, it is sufficient to replace it.During operation, the cover of the coupler burned out ... This is a kind of plastic cap that rotates the pallet. In this case, only replacement will help. Naturally, it is necessary to install a coupler from the same type of model, since the design of such a cover may be different even from one manufacturer.The "wrong" dishes are installed in the chamber ... We remind you that metal appliances, as well as those on which metallized dyes are applied, cannot be used in microwave ovens.First of all, it is necessary to check that the pallet is not blocked by any foreign object, it is correctly installed or the separator. If everything is normal, then the reason lies in the drive. This may be due to the following reasons:
Jammed engine (determined tactilely) or breaking one (dialing is carried out) of the windings. In these cases, a replacement of the drive is required.Gearbox problem ... In this case, it all depends on the design. In some cases, the gearbox can be repaired. But, as practice shows, it will be easier and cheaper to replace it.In modern electronic models, such a malfunction indicates a problem with the control module. In products with an electromechanical control system, it makes sense to check the mechanical relays and / or switches, if necessary, replace defective parts.
If, when turned on, the power indicator lights up, but the digital display does not work, then everything indicates problems with the control module. It needs to be repaired or replaced.
Video (click to play).
A characteristic indicator of faulty microswitches for door position. One of them is "stuck" and does not switch; as a result, a short circuit occurs in the control circuit. The repair consists in replacing or cleaning the microswitches.
