Common faults of microwave ovens

There are many types of problems, such as not starting, not working, (insufficient firepower), intermittent work, the presence of open flames, and non adjustable firepower, which are described below.
Note: If it is necessary to disassemble for inspection and repair during maintenance, unless otherwise specified and checked for the 220V power supply voltage of the "no start" fault, it refers to the maintenance conducted after unplugging the power plug, powering off, and discharging the high-voltage capacitor.
1. Not working
Failure to start refers to the failure of the microwave power connector to work normally after closing the furnace door. It is one of the common faults in microwave ovens, and also a fault involving a wide range of circuits, which is relatively difficult to check and judge. In order to facilitate everyone to quickly understand and master the methods and skills for judging and repairing such faults,
Common main reasons for non startup failures include:
The fuse tube is blown, the overheat fuse is open, the power circuit is faulty, and the safety interlock switch is poor or damaged. The fault diagnosis and handling of the power supply circuit is relatively easy, and it will be mentioned below. Here, we mainly discuss the troubleshooting problems of the safety interlock switch, which mostly lead to non startup faults, The main cause of a problem with the monitoring interlock switch is a failure of the fuse tube during startup (the fuse tube cannot be started after it is broken). For example, the main interlock switch should be turned on when the furnace door is closed. If the open circuit is damaged, the microwave oven cannot be turned on and started regardless of whether the furnace door is open or closed.
2. Insufficient heat
Insufficient heat, also known as slow heating, refers to the fact that compared to normal use, microwave ovens use significantly more of the same firepower than normal use. This failure is a manifestation of reduced microwave output power. Under normal power supply conditions, the main reasons for this failure are aging of the magnetron or low supply voltage of the magnetron filament or anode.
There are two types of aging of magnetrons. One is natural aging due to too long a service life. Generally, the design service life of a magnetron is related to the output power of the magnetron, which is not immediately significantly reduced, but gradually aging. Therefore, naturally aging magnetrons are rarely encountered. Another is premature aging. The main reason for this failure is the poor quality of the magnetron itself or the fact that it has been operated for a relatively long time in harsh environments, which is usually rare. Therefore, when repairing a lack of heat fault, it is usually advisable to first check the power supply voltage of the magnetron filament or anode (check its power supply circuit and connection terminals when power is off), and pay attention to the contact condition of the connection terminals of the magnetron filament pins. Especially, microwave ovens that have been used for a long time are more prone to poor contact faults.
Looking at the magnetron filament pins and their connectors, it is often found that the pins are corroded and have an oily green dirt layer. If the connectors are loosely connected to the filament pins, the contact resistance will significantly increase, causing the filament voltage to be too low, which significantly reduces the output power of the microwave oven. To repair this fault, simply remove the dirt from the filament pin, wipe it with an alcohol cotton ball, and then use pointed-nose pliers to flatten the pin connector to make good contact with the filament pin after insertion.
If there is no problem with the power supply, the magnetron is basically aging. This can be confirmed by replacing the magnetron, measuring whether the filament resistance of the magnetron is normal, and checking whether the magnetic steel is cracked. For the failure of insufficient heating caused by aging of the magnetron, it is usually the perfect solution to replace the tube. In addition, if the capacity of the high-voltage capacitor is significantly reduced, it will significantly reduce the anode voltage and output power of the magnetron, and also cause insufficient heating. However, this situation is rarely encountered, and failures of the high-voltage capacitor are mostly due to breakdown or open circuit.
It should be noted that in practice, we have found that the failure of insufficient heating is often related to the 220V power supply voltage, and often has a certain degree of confusion. However, due to the large internal resistance or contact resistance of the power supply line, the large current flowing through the microwave oven during operation forms a large voltage drop on the wires or connectors, making the actual working power supply voltage of the furnace significantly insufficient, resulting in slow heating. The large internal resistance of power lines usually exists in power wiring boards, fuse sockets, power line connectors, or power lines. Although the internal resistance is large, the no-load measured voltage is often normal, so it has a hidden confusion. Therefore, during maintenance, it is necessary to pay attention to and solve this problem first, so as to avoid further detours.
3. Clearance work
Gap operation refers to the automatic power off after the microwave oven is started up, and then automatically starts up after a period of operation. If this cycle is repeated for many times, the microwave oven will not start up after the automatic power off. The main reason for this failure is that the magnetron overheat protector is faulty and stops working. When the operating temperature of the magnetron overheat protector is too low, the temperature of the magnetron rises to the operating temperature of the overheat protector after operating for a period of time, and the protector cuts off the power supply of the microwave oven. After a period of time, the magnetron temperature drops to the value that the protector recovers from itself, and the microwave oven power supply is turned on again to start working. This cycle forms an intermittent working phenomenon. It is convenient to check and judge such faults: excessive temperature may cause faults such as shutdown shortly after startup. Most temperature protection devices are 145 ℃ protectors, and a few use around 130 ℃ protectors; The types of furnace cavity overheat protectors are mostly around 80 ℃
4. Open flame appears
This refers to the ignition phenomenon that occurs in the use of microwave ovens. Lighter sparking only allows you to see an open flame in the furnace. Most of these failures are caused by excessive no-load capacity. The solution is to increase the power level.
5. Power is not adjustable
This kind of failure is basically caused by the power controller, which only needs to be repaired. There are often two situations when a power controller is damaged. One is that the power adjustment knob cannot be rotated and adjusted, and it always stays in a certain gear, but the heating and other functions are normal. This is usually caused by foreign matter blocking the plastic adjusting gear rod and other parts of the power controller. The power control/timing integrated assembly can be removed, removed, and then reinstalled to solve the problem. The second is that although the power adjustment knob can be rotated and adjusted at will, the firepower of the microwave oven does not change with it, and it always works at a fixed firepower level (usually at a high level). This is caused by the failure of the power controller adjustment function. You can remove the power controller and timing components, and check whether the power control switch and timing motor are damaged. If serious damage is found, it should be replaced.

The above content is organized by Superb heater Company, super heater. Mainly professional production: industrial heating elements, temperature measuring elements, production equipment, accessories, and raw materials such as tubular heaters, tubular heaters, belt heaters, ceramic heaters, silicone rubber heaters, thermocouples, etc.

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