In detail: do-it-yourself rolsen microwave repair from a real master for the site my.housecope.com.
To repair a microwave oven, you need to have a general idea of how it works. Microwave oven repair begins with removing the top cover. Before that, you should take care of completely disconnecting the device from the power supply, only then proceed with the elimination of breakdowns with your own hands.
When these steps are successfully completed, a transformer with two fuses will open for access: one is located directly on the part itself, it is fusible, the second is located nearby on the very body of the microwave oven, made of ceramics. Also next to the transformer is a doubler block consisting of a thick capacitor and a diode. The whole set of these elements is the power supply circuit of the microwave oven magnetron.
Carefully! Do not touch the condenser immediately after removing the top cover. This element is capable of holding voltage for a long time, which can easily lead to an electric shock. When repairing a microwave oven with your own hands, this factor should be taken into account.
The peculiarity of microwave ovens is that all parts are connected in series. First, you should pay attention to the above magnetron and its power supply circuit. After removing the protective housing, a transformer with a large capacitor located next to it becomes accessible. There will also be a ceramic, low-melting fuse, a diode. The magnetron operates according to this high voltage circuit. Under no circumstances should you get into it with your hands, tools. After a complete de-energization, the capacitor will lose its residual voltage, the likelihood of an electric shock will decrease.
Video (click to play).
The primary winding of the micro-transformer takes over 220V. As a rule, its location is at the bottom. You can recognize it by the coils of copper wire, which in appearance will be bare. However, it is not. It is covered with a transparent insulating film. The location of this coil is under the secondary winding.
The microwave oven has two secondary windings. On one of them, several turns of a simple wire are usually not neatly wound. This heats up the cathode. Here the AC voltage is only 6.2V so that the electrons can be lifted from the surface. But where there is good insulation, there is a high voltage winding. About two kV directed towards the exit.
A capacitor shunted by a diode is located at the output of the circuit. The action of the negative half-wave falls on the cathode, the action of the positive half-wave charges the capacitance. Further, the electrode is subjected to double voltage, which is removed from the capacitor and the micro-transformer. As a result, approximately 3.5-4 kV is created. This power is enough to start the generation process.
You should be extremely careful, the output winding is always parallel to the magnetron, which has two output options. But the grounding of the anode is done in a separate way.
Thus, this is what happens:
the heating coil has 6.3V;
at the cathode stays up to 4.2 kV, grounded by the anode.
All microwave ovens have an electrical connection for the cathode, heating coil. Each microwave oven is equipped with a timer that controls the magnetron power. The use of a start relay is used in order to avoid the occurrence of a spark. Next, you should pay attention to the front panel.
The most likely breakages occur in the area of the mica plate. Energy is supplied from the magnetron to the waveguide along the rod. The latter is highly sensitive to the presence of various food debris. All these contaminants begin to ignite, emit sparks, thereby disrupting the stable operation of microwave ovens. To avoid unforeseen situations, the developers decided to close the waveguide with a mica plate. It has soft, flexible properties, relatively affordable pricing. It will not be difficult to fix such a breakdown with your own hands. You can buy material of any size, cut the corresponding segment. The peculiarity of the mica plate is that it transmits a frequency level of 2.45 GHz without obstacles. It is at this frequency that the microwave oven operates.
Also, mica plates do not get wet. This is a very important factor if liquid is heated inside microwave ovens. After all, water very quickly absorbs the radiating frequency of 2.45 GHz, there is a danger of serious damage. If the water reaches the waveguide, a big accident is created, which will not be easy to repair with your own hands. The high voltage fuse will blow instantly. If everything gets worse, the magnetron itself burns out, other electronics that power the microwave oven.
What factors influence the destruction of the mica plate? Most reheated food contains a lot of fats, oils, and other such ingredients. They differ in that instead of the usual boil, they shoot out greasy drops. Once such a drop hits the mica plate, a small wire bridge is created. An electric arc is formed: from the waveguide to the mica plate, then from it to the body of the microwave oven. As soon as pops and sparks, uncharacteristic for the operation of stoves, appear, this is a sure sign that the stove will soon need to be repaired.
Anyone who has tried to fix a microwave oven with their own hands wondered about the high-voltage fuse. The mechanism of microwave ovens of this kind triggers at least two fuses:
If you look at the electronic board of the microwave, this part appears as a small white or transparent cylinder. Its task is to protect integrated, wall-mounted microwave oven components. This small cylinder is also part of the power supply circuit. Its burnout occurs in the event of a capacitor breakdown, a resistor short circuit.
The circuit that forms the power supply of the magnetron includes a diode, a transformer, and a capacitor. Through them, about two or three kilovolts approaches the cathode. These details are not difficult to find. It is difficult to confuse the appearance of the capacitor with anything else. This is a huge detail in the form of a jar weighing up to one hundred grams. One diode leg is attached to it, the other is fixed to the body. Nearby is also a small barrel, often ceramic, painted in brown. It is this barrel that contains a high-voltage fuse inside it. Its task is to prevent overheating of the magnetron. When a mica plate breaks through or a metal spoon is placed in the microwave oven, the high-voltage fuse immediately burns out.
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:
If the oven door is open, the relay trigger is released.
In this operation, the power supply circuit has two breaks.
The second relay closes the ground on the phase.
When the first relay is energized, nothing bad will happen as the power supply circuit is in the open position.
When the first relay sticks, the fuse kicks out. This is due to the fact that the ground was short-circuited by a phase.
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.
Do-it-yourself microwave repair is possible, but only for those users who are at least a little versed in electrical engineering and have experience with hand tools.
Microwave repairs are easier to prevent. To do this, do not use the device in conditions that cause critical modes of operation of its components. The documentation supplied with the microwave oven describes the operating rules and warnings in sufficient detail. For example, that food should not be reheated in metal containers, that the appliance should not be turned on with an empty chamber, etc.
Burnt out mica plate
It is necessary to monitor the condition mica plate microwave oven, which closes the window of the waveguide that transmits radiation into the oven space. Regular cleaning will prevent microwave oven repairs caused by burnout, as well as sparking and short circuits (read about replacing a faulty part in the article with how to replace a burned-out mica plate in a microwave).
The microwave should not turn on if there is nothing inside. This causes a critical mode of operation of the emitter and reduces its service life. This action also negatively affects the state of the magnetron, and this part costs almost like the microwave itself.
Do not operate the device if sparking is observed, violation of the integrity of the mica plate (this indicates that the elements of the magnetron are damaged or it is operating in a non-standard mode), transformer humming, malfunctioning of the control electronics. In this case, if you do not have the skills to work with equipment, it is better to call a qualified specialist.
The main elements of the microwave oven
A failed magnetron is the cause of most breakdowns. In order to identify a malfunction, it is necessary to carry out the following operations:
Disassemble the device. Dismantling the microwave oven begins with removing the side cover or completely dismantling the top casing. This is not difficult to do. Sheathing elements are fastened with screws or bolts, usually they are not even hidden. Dismantling the housing to access the electronic components can be seen in the video below. However, if we are talking about Panasonic microwaves, it is worth remembering: one of the fasteners may have a seal, the destruction of which will void the warranty.
Remove the magnetron unit. It is secured with four screws and can be removed easily.
