Microwave Panasonic DIY repair

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.

1. 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 will be bare in appearance. However, it is not. It is covered with a transparent insulating film. The location of this coil is under the secondary winding.
2. 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.
3. 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 things get 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 the microwave with their own hands wondered about the high-voltage fuse. The mechanism of microwave ovens of this kind triggers at least two fuses:

1. 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.
2. 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:

1. If the oven door is open, the relay trigger is released.
2. In this operation, the power supply circuit has two breaks.
3. The second relay closes the ground on the phase.
4. When the first relay is energized, nothing bad will happen, since the power supply circuit is in the open position.
5. When the first relay sticks, the fuse is blown 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.

Microwave (microwave) Panasonic NN-G335 oven is a very successful model, both in design and in functionality. Until now, this model has not been discontinued, but only underwent a slight restyling. The oven has an exceptionally convenient handle for opening the door, equipped with a grill and electronic (touch) control. Despite the relatively high price in its class, the Panasonic NN-G335 microwave oven is in great demand among buyers. What is the furnace in operation in terms of the reliability of the electronic and mechanical components?

Corroded bottom of the chamber.

After about three years of operation, through corrosion of the bottom of the chamber formed. The high humidity and friction of the turntable wheels are likely to be the cause of the corrosion. Immediately after the discovery of such a defect in the chamber, the furnace was checked for radiation leakage with the help of a microwave detector. Everything turned out to be normal. The outer casing shields well despite the major destruction of the camera.
In the second year of operation, the camera illumination lamp burned out. The breakdown is not at all terrible and easily removable. You need to: open the oven (remove the cover), disconnect the wires on the lamp, remove the lamp and install a new one. However, the lamp there is used not ordinary, but a special one for microwave ovens (the base is not threaded, but in the form of two contacts). Buying a lamp is not particularly problematic. As a last resort, you can put an ordinary lamp, having come up with a way to fix it and connect the power wires.

Backlight lamp.
Shines through small through holes directly into the camera.

In the third year of operation, at one "fine" moment, the furnace refused to work at all (the display did not light up, there were no signs of life). After opening the case, first of all, the thermostats were checked, and a malfunction was immediately found - one of the thermostats was in a permanently open state. There are two such thermostats in the Panasonic NN-G335 oven, both operate to open when their body is heated above the nominal response temperature (indicated on the thermostat body). In order to replace a failed thermostat in any microwave oven, you need to know the response temperature of the failed thermostat, its operating current, the type of switching (on or off) and the type of case (appearance). We could not find the same thermostat (by fixings). This is not scary, the main thing is to ensure reliable thermal contact of the thermostat body with the body of the investigated object (details of the furnace structure on which it is installed).

"Live" thermostat in the standard setting (photo on the left).
Replaced thermostat. Installed with an additional pressure plate and self-tapping screws (photo on the right).

It is difficult to say what was the reason for the failure of the thermostat. Most likely, the reason is simply in time, because everything has its own service life. If overheating took place, for example, due to the closing of the external ventilation slots by something, then after turning off the oven and cooling it down, a working thermostat should turn on again, which did not happen.
And the last thing I had to face was the blown of the power supply fuse as a result of the operation of the protective diode.

Power board with blown fuse F1 removed (photo on the left).
Power board, speaker view (buzzer). The hole marked with a red circle can be sealed, for example, with electrical tape, and the microwave will not beep loudly (photo on the right).

Protective diode 2X062H mounted on a high-voltage capacitor 1 μF x 2100 V (photo on the left).
The inscription on the high-voltage capacitor (photo on the right).

In order to find the reason for the operation of the protective diode 2X062H and, as a consequence, the blown out of the fuse, the resistance of the magnetron heating circuit was checked, it turned out to be extremely small (about 0.1 Ohm), it was not possible to accurately measure it with an ordinary multimeter. According to the found reference data for this magnetron, such a low resistance was normal for a working magnetron, or rather, should be 0.07 Ohm. The resistance between the magnetron body and its terminals was also checked, the resistance turned out to be "infinite", as it should be. From these measurements, it was concluded that the magnetron was in good condition (for lack of the possibility of a deeper test). However, when dismantling the magnetron and removing the protective metal cover, traces of excessive local heating of the coils were revealed (the enamel of the insulation had darkening), but the wire itself was not damaged. To ensure the conditional serviceability of the high-voltage transformer, the DC resistances of all its windings were checked. The resistances roughly coincided with the reference data. The measurement results were written with a pen on the transformer itself for the possibility, if necessary, to re-check the measurements in the future.

Magnetron Panasonic 2M211 (photo on the left).
View of the furnace with the removed magnetron (photo on the right).

Magnetron.A slightly burnt insulation of the coil is visible (photo on the left).

Magnetron. The cover is removed (photo on the right).

As a result, it was decided to replace the fuse with a higher current (10A), assemble and check the furnace in operation. As it turned out, this decision was correct. After the last repair, the microwave oven works perfectly, no extraneous noise or abnormal operation was observed. Of course, if repaired according to all the rules, then it was also necessary to replace the burnt out protective diode with a new one, but its far from the lowest price, the absence of radio supplies in the vicinity of the store and the extreme need for a kitchen in the oven outweighed the rest of the arguments. At the end of the article, you can see a few more photos of the repair process.

High voltage transformer. View of the nameplate (photo on the left).
The resistance of the high-voltage transformer windings was measured with a Mastech M-838 digital multimeter (photo on the right).

Contact to body one of the terminals of the transformer winding (during testing, it is necessary to check the presence of this contact with a multimeter).

Everything is connected.

Rectifier diode. Body contact (in red circle).

Many of us have forgotten about various stoves, hobs and completely trust the process of cooking microwave ovens. And this is not surprising at all: microwave ovens take up little space, have a rich set of different functions and significantly save time. Naturally, we are very upset when our microwave breaks down. The reasons for the breakdown and malfunction can be different. Consider what breaks down most often in a microwave oven. Often, if a microwave oven breaks down, it is necessary to contact a specialized master. After all, this is not the simplest device, so the repair is rather complicated. But in fact, the design of a microwave oven is elementary and includes only a few basic elements. If you first familiarize yourself with frequent breakdowns, then repairing the microwave on your own will not be difficult.

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 outwardly the design is not very complex. The magnetron is always installed in the middle, directed towards the food warming 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 is already flowing out of the element. Further, the negative half-wave goes to the diode, and the positive one charges the capacitor, which again leads to a twofold increase in voltage. After that, the generation of microwaves by means of a magnetron begins. The power of the magnetron is regulated by the control unit.

Therefore, in the event of a breakdown, it is worth paying attention to these elements. They carry the greatest load, so they are often the problem.

When disassembling the microwave, be sure to disconnect it from the mains.

Search for breakage in a microwave oven is based on "symptoms". This allows you to gradually exclude possible causes and find the real one. So, if the oven does not turn on at all, then it is worth checking the following points:

• The integrity of the power cord.
• Door position and closing system.
• Mains fuse and thermal relay status.

In the first case, the situation is elementary - there is no power supply due to damage to the power cord. A similar situation occurs when the outlet is damaged or overloaded. In this case, it is enough to replace this element, everything is in order with the microwave itself.

Next, it is worth checking the operation and position of the door. The fact is that the operation of a microwave oven when the door is open is dangerous for others. Therefore, the design provides for the possibility of operation only when it is completely closed. If a latch, a locking system or a checking element is broken on the door, the protection system will not allow the device to start.

The last points also concern the protective systems of the oven. The fuse prevents damage to the device due to power surges, and the thermal relay provides a complete shutdown of the system when the door is open. Both can fail, it is quite easy to replace them.

It is also worth checking the voltage in the network and the number of devices connected to the outlet. The microwave oven is very demanding on power supply, therefore its slight deviations can interfere with the operation of the appliance.

Procedure if there is no heating Fuse faults

Most models suffer from common problems and have similar, typical faults. For example, if the microwave works, but does not heat, then this indicates a malfunction of the capacitor, diode or magnetron. To repair a microwave oven yourself, you will need a simple set of tools: pliers, wire cutters, a screwdriver, an adjustable wrench and a five-spanner wrench, as well as a soldering iron with the necessary equipment.

When repairing a microwave microwave yourself, you should remember about safety measures. The two most important hazards in microwave oven repairs are high voltage in oven components and microwave radiation. Do not turn it on if the door is defectively locked or the mesh on the viewing window is damaged. Do not make independent holes in the case and introduce any conductive objects into the units and elements of the furnace. Never touch internal parts and assemblies while the microwave is in operation.Be sure to use a tester or other electrical meter to measure AC and DC current.

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

Fuse

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

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

Photo of a microwave condenser

These elements are directly involved in the operation of the device and were mentioned earlier. First you need to check the health of the fuses. Their breakage can be seen immediately, because during combustion, the conductor inside is destroyed. If this did not happen, then it is worth looking further.

For further verification, you need to take a multimeter, because outwardly 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, then the part must be replaced.

High voltage diode

It is impossible to check the high-voltage diode with a tester. It is recommended to replace it in case of breakage of other parts, because often the blow falls on it. It can be checked in a slightly different way - by connecting it to the network on the way to the light bulb. If the light is weak or blinking, then the part is working properly. If it burns brightly or does not turn on at all, then the diode must be replaced.

Next, the transformer is checked.

Photo of a microwave transformer

It is important to observe 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 serviceable transformer, and if the discharge resistor breaks down, it will take much longer. It is worth discharging it on the case or not touching it at all if there is no experience with such a technique.

Next, the transformer windings are checked. It is necessary to remove the terminals and check the terminals of the device one by one with an ohmmeter. First, the primary winding is checked, for which the rate 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 the 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, just connect the tester to its power terminals. The tester switches to ohmmeter mode. If the resistance is 2-3 ohms, then this means a breakdown of the device. The situation is the same if the tester reads infinity. In both cases, the device must be replaced.

These items are the most common culprits in microwave oven breakdowns. However, the failure of the device is often associated with other malfunctions, 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 needed. Although it is much easier to simply replace a part if you are sure that it is broken.

There are frequent cases of breakage associated with the destruction of the cap on the magnetron. The thin aluminum body simply cannot withstand stress and is destroyed by microwave waves. This problem often occurs in older devices that are more than a few years old. The obvious symptoms in this case are noise and sparks during the operation of the device.

To check, it is enough to remove the transformer, because the cap is located towards the food chamber. If the cap is destroyed, then there are 2 options:

• Cap replacement.
• Flip the cap.

The first option is a priority, it is enough to order a replacement or return the magnetron for repair. The second option is considered a temporary alternative that allows you to extend the life of the device indefinitely.It is enough just to rotate the cap 180 degrees around the axis, because the load falls on only one half.

Repairing a microwave oven is a feasible task for a novice electrician. If the problem lies in the breakdown of one of the constituent elements of the furnace, then the simplest and correct solution is to replace it. The bottom line is that most of the parts of this device cannot be repaired, but only completely replaced with a new one. This especially applies to fuses, diodes and capacitors - the main reasons for the failure of the device.

Parts replacement is carried out in several steps:

1. The microwave is disconnected from the network.
2. The transformer is discharged (5 minutes).
3. The terminals are disconnected from the defective part, it is removed.
4. A workable part is connected to the same place.

There are two important factors to consider when replacing a part. The first is schema compliance. It is important to remember that each part has its own characteristics, selected for the performance of the entire electrical circuit. If, after replacement, this nuance is not taken into account, then this leads to new breakdowns. This is especially true for the transformer and capacitor.

The second important factor is the connection of the part. It is necessary to connect the replacement correctly, keeping the previous arrangement of the terminals. Reconnecting the device in reverse order can damage it, as well as several other parts in the system.

This will restore your microwave in most cases. If the breakdown is related to the electronic part of the device, then you should contact the professionals. This will ensure quality repairs and prolong the operation of the device for a long time.

The most common malfunction is the failure of the waveguide cover in the microwave oven chamber. This is caused by splashes from cooking. This starts sparking between the magnetron antenna and the protective cover. Untimely removal of burnt products leads to local burnout of the lid and to complete destruction.

Local burnout of the lid mica plate can be removed with alcohol or solvent 646. It is enough to gently wipe the burnout area.

Burning out mica

If the mica plate of the lid is clearly in poor condition, is greasy or begins to paint, then it should be replaced. Removing the diffuser plate is a snap. This can be done using an ordinary sharpened knife. Usually, the mica plate is attached with a self-tapping screw or rivets. Carefully place the old plate on the new template and cut out a new one. The best way to do this is with a knife - you can break the mica with scissors. We make holes in the new plate with a sharp screwdriver and process the edges of the fields of the plate with sandpaper. We install the new plate in place of the old one.

The question often arises, how to replace mica for microwave ovens? For these purposes, any dielectric with a similar dielectric constant is suitable. For example, PTFE or Teflon.

Common breakdowns in a microwave oven are also malfunctions associated with other elements of the oven. For example, such as the keyboard of the oven control unit, the microwave oven electronic control unit and the dissector. Less often, the high-voltage capacitor and transformer, the microwave waveguide plug and the rotating pan fail. The power supply and magnetron of the microwave oven are subject to wear and tear.

Knowing how to troubleshoot microwave ovens can save you significant repair costs. However, if you do not know how to repair the microwave yourself, then it is best to contact a specialist. Specialized service centers will help you to repair a microwave microwave oven. In addition, watch the video on microwave repair, perhaps there is exactly that breakdown that will help you fix your beloved household assistant.