The most common external signs of a microwave oven malfunction include sparks, clouds of smoke, the plate stopping rotation, the lack of heating of food placed in the oven, or the microwave simply not turning on. In such cases, it is dangerous to plug it into the power outlet!
There are three main reasons why a microwave oven may malfunction:
- Blown fuses;
- Magnetron malfunction;
- Burnout of the mica plate.
Blown Fuse
This is the most common cause of a malfunction. A microwave has two fuses. The first, known as the line fuse, is located at the input of the 220-volt power supply to the microwave oven. This fuse can blow, causing the oven to stop turning on and become unresponsive to any button presses. The first step is to diagnose the microwave: remove the screws on the back and open the protective panel. Remember to unplug the microwave before starting any repair work. Next, you need to forcibly discharge the filter capacitor by shorting its leads using an insulated wire. Be sure to hold the wire strictly by the insulation. After this, check for voltage on the line filter board and inspect the power wires of the microwave for faults.
If no issues are found in this part, you should check the diode in the rectifier circuit of the power supply, as it is often the cause of the fuse blowing in this type of malfunction. The fuse in the microwave should be visually inspected for a break or checked with an ohmmeter. If necessary, replace it with a functional one and analyze the causes of the fuse blowing to prevent a similar situation, paying attention to any discoloration of the radio components, which may indicate faults in the microwave’s circuits.
The second fuse is located after the high-voltage transformer in the magnetron circuit and is called the high-voltage fuse. It is “hidden” in a plastic tube housing and is located next to the transformer. This fuse fails due to the failure of the high-voltage diode or capacitor. It’s best to replace the fuse with a new factory-made one because it is calibrated for the required tripping current. And, of course, be sure to replace the part that caused the fuse to blow.
Magnetron Malfunction
If the oven’s light is working, the plate is rotating, but the microwave isn’t heating food, the most likely cause is a magnetron malfunction. The magnetron is a device that generates microwave radiation, which is why when this part fails, the oven doesn’t heat.
The magnetron is housed in a small rectangular metal case. First, it should be cleaned and then visually inspected. Next, check the magnetron block itself, particularly the integrity of the wires connecting the terminals and the housing. Often, the cause of a non-functional magnetron is a faulty bypass capacitor. After this, be sure to check the microwave’s control unit. Again, pay attention to burnt, sooty, or dirty areas. These components will need to be replaced to restore the microwave’s functionality.
Mica Plate Burnout
A sure sign of a mica plate malfunction is sparks that appear when the microwave is turned on. The cause is improper use of the oven, such as heating food with the lid open. In such cases, food splatters and gets onto the plate, causing it to become wet and burn out.
A mica plate is inexpensive and can be purchased at specialized electronics stores. If you find a mica plate of different dimensions, you can cut it to the required size yourself.
If you can’t find a replacement for this part, you can reuse the burnt plate. To do this, remove the plate and carefully clean it. Then, turn it so that the damaged side faces inward and reinstall it. While this repair option isn’t ideal, it will suffice until you find a replacement for the damaged part.
If you still haven’t been able to fix the issue even with our advice, and the microwave still isn’t heating, you may want to repair the microwave with a professional or purchase a new one. The decision depends on the extent of the damage and how much money you’re willing to spend.