Each house has microwave. This is a very handy compact device. In a matter of minutes, it will heat up food, provide thawing of food frozen in the freezer, it is not difficult to use this unit. Microwave ovens work reliably, but sometimes they fail. It is not always necessary to contact the repair service. Some faults can be corrected by hand.
Read in the article
- 1 The device and principle of operation of the microwave oven
- 2 External signs of oven malfunction
- 3 Blown and repair of fuses
- 4 Microswitches
- 5 Malfunction of the magnetron
- 6 Burnout of the mica plate
- 7 Conclusion
The device and principle of operation of the microwave oven
There is a general rule - before proceeding with the repair, you need to understand how the furnace is arranged and how it works. In the composition of the furnace, four enlarged structural elements can be distinguished:
- generator of high-frequency electromagnetic radiation - magnetron;
- means for transporting the generated radiation to the heating object - a waveguide;
- power transformer with two windings;
- a working chamber in which food is heated.
If you do not get into the jungle of physics, then the further explanation will be simple. Under the influence of electromagnetic radiation with a frequency of 2.4 GHz, the molecules of the substances that make up the food begin to move rapidly, and the food begins to heat up. Radiation is created in an electrical device called a magnetron. A power transformer of the magnetron is installed here, which provides 3 V for the filament and 2000 V for the operation of the emitter. The doubling circuit raises it to 4000 V. And also the electromagnetic circuit-emitter itself, which directs radiation through the antenna into the waveguide and further into the working chamber. The electric circuit of the furnace is powered by a power transformer.
The safety of the oven during operation is ensured by the presence of two limit microswitches that interrupt all power supply when the door is open. Radiation from a magnetron has a harmful effect on humans, the metal case is a protective shield. The electric part of the furnace includes the electric motors of the fan cooling the magnetron and the plate drive. The presence of fuses protects the elements of the electrical circuit from serious accidents. Microwave ovens produced by different companies work according to the same principle and are equipped with almost the same electrical equipment.
External signs of oven malfunction
At some point, the hostess may pay attention to the fact that the oven does not work as usual, or does not work at all. The most common external signs of a malfunction that has appeared:
- The microwave oven does not turn on when you press the power button;
- when the door is closed, the fuses blow out;
- the oven continues to work after the end of the set time;
- insufficient heating of products;
- the oven is turned on, but heating does not occur;
- sparks appear in the chamber when turned on;
- the pallet rotates in jerks;
- when the oven is switched on, the control panel does not work.
The main reasons for the failure of an electrical appliance are:
- blown fuses;
- malfunction of the end microswitches;
- malfunction of the magnetron;
- burnout of the mica plate.
Blown and repair of fuses
One of the most common malfunctions is a blown out of one of the two fuses installed in the furnace. For any repairs, the stove must be de-energized, i.e. disconnect from the mains. You just have to pull the power cord out of sockets. And after removing the protective cover, it is necessary to discharge the filter capacitor. All the time it is necessary to follow the rules of electrical safety.
The first, mains fuse F1 is installed at the mains voltage input. If it is he who burned out, then not a single function of the furnace will turn on, not a single light will light up, and the motors will not spin.
After removing the cover, you should:
- First, conduct a visual inspection of the wiring for the quality of the wires and contacts.
- Inspect all accessible elements, darkening of the part body may indicate its overheating.
- The fuse itself is also first checked visually, and then using a dial.
- Then you should check the rectifier diode of the power supply. It needs to be checked for breakage and breakdown.
- If the diode is defective, it should be replaced and the fuse can be tried to be repaired. But this should be done only if it is impossible to quickly acquire a branded one, and the oven is very necessary for business.
The repair boils down to the fact that the bulb of the faulty fuse is carefully disassembled, a copper wire of a suitable diameter is soldered into it, and everything is neatly assembled again. The oven will work, but the product should be replaced with a branded product at the first opportunity.
The figure below shows the location of the oven fuses. In the upper part is the mains fuse F1, in the lower right corner of the photo you can see the high-voltage fuse F2.
The second high voltage fuse F2 is installed behind the high voltage transformer in the magnetron control circuit. It has a plastic case. The cause of its failure may be a malfunction of the high-voltage diode or capacitor. You should not repair it yourself, it must be calibrated to the desired operating current. But it is imperative to identify the faulty radio component and replace it, otherwise the fuse will burn out again.
Microswitches
In the microwave oven, three microswitches are installed on the body. They are triggered when the pins on the right edge of the door enter the housing. If, when the door is slammed, the light does not light up, the pallet does not spin, the magnetron cooling fan does not work, or other malfunctions appear, then these "mikriki" must be checked for the quality of operation. A defective one should not be repaired, but replaced. The figure below shows the oven area (at the back on the left edge) where these devices are located.
Malfunction of the magnetron
If, when the oven is turned on, the light is on in the chamber, the pan is spinning, but there is no heating, then this absolutely means a malfunction of the magnetron. Because it is the magnetron that generates high-frequency radiation, which leads to the heating of the product.
Access to the magnetron is opened after removing the back cover of the furnace, then:
- The first step is to wipe the block from dirt.
- Inspect, check all wires and terminals.
- In fact, a breakdown of the bushing capacitor may be the cause of the malfunction. In this case, it will be necessary to disassemble the magnetron, check and remove the faulty capacitor, install a new one and assemble the unit.
You should take on its repair only if you have the skills to work with electrical equipment and self-confidence.
There is a high voltage diode in the magnetron circuit, which can also fail. It must be checked and, if necessary, replaced.
Burnout of the mica plate
If you look into an open microwave oven, then on the right wall you can find a small dark rectangle screwed with one bolt. It is dark because from the long operation of the stove it is splattered with pieces and drops of food. It is a protective mica that allows high-frequency radiation from a magnetron to pass into the furnace chamber, but at the same time withstands high temperatures. But sometimes it still burns out, and then, when turned on, the stove sparks. This means that the mica must be replaced. It is inexpensive. You can buy larger sizes and trim them later.
Conclusion
The microwave oven is not a simple unit. But if you take the matter of repairing it seriously, carefully read the instructions, besides, have basic knowledge of electrical engineering and be able to work with your hands, then the repair of the furnace can be carried out successfully. The main thing is to follow the rules of electrical safety, do not forget to put in place the removed elements, which have already been checked and are in good working order. Defective - discard immediately.