Panasonic Microwave Oven Operates Thanks To Recycling
I have never worked on a microwave oven before. In fact I had no idea how they worked. So when a friend bought his in for repair, I realised that it was time for me to do some research. I was surprised by their simple design.
Microwave ovens operate due to 2 main components – the transformer and magnetron. The transformer outputs a high voltage of about 4 kV. The magnetron uses a form of vacuum tube. By applying a high voltage at the centre filament, electrons are ‘boiled off’ this filament and fly to the circular copper anode cylinder. Two magnets are fitted at either side of the centre filament and these are used to ‘bend’ the electron path back toward the centre filament. The magnetic strength is adjusted to get these electrons to just brush past the vane openings. This in turn creates an oscillating wave – the microwave radiation used to heat the food.
The microwave oven was invented by Percy Spencer. In 1939, while working for the Raytheon company, producing magnetrons for use in radars, he noticed that a chocolate bar had melted in his pocket while he was standing near an active radar. He purposely tried to heat a corn kernel and popcorn was created. By enclosing a magnetron in an enclosed metal box, the electrons became concentrated. Raytheon filed for a patent in 1945 and the first commercial microwave oven named the ‘Radarange’ (weighing 750 lbs, 6 feet tall and costing $5000) became available.
As my friend bought in his microwave, he passed by mine and discovered that they were identical! At least I would be able to do some reference testing if required. I just had to make sure that my wife didn’t know what I was up to!!
This microwave operated, had a light and also circulated the plate. The main complaint was that there was no heating. I confirmed this with a glass of water. After removing the cover I was able to divide up the circuits. After testing the transformer, my next step was the magnetron. More Research!!
They seem very simple, but how do you test them? I found an internet site that gave me a few clues about how to test it.
In the meantime, I had to make a trip the recycling depot. They allowed me to bring some items home, which included (believe it or not) an identical microwave oven to both mine and the one I was working on!
Here is how I tested the oven from the recycling depot and then compared it to the inoperable one. I was unsure about the safety of this test, but by putting any metal in water, the energy is dispersed into the water and will not bounce off the metal. Just to be sure, I carried out this testing outside and also while my wife wasn’t home!
TESTING THE MAGNETRON
See the photos below:
You may also click on this link to watch the video.
Notice the light flashes off and on as the electric and magnetic fields change rapidly. This test proved that the recycled oven operated correctly. Further testing proved this to be the case. Why do people throw out perfectly good items? We live in a throw-away society. Frustrating!! I’m sure you would all agree.
I further pulled down the faulty microwave and noticed several things. The plastic cover that holds the light bulb in place was melted and also there were slight burn marks on the magnetron cooling fins.
I also noticed that one of the magnets was cracked and apparently this is a common fault with magnetrons.
I priced a new magnetron and the customer decided that he would get a new microwave oven. But now that I had a recycled part, he was happy to have the item back at a cheaper price.
Replacing the magnetron took only a short period of time and after doing so, I carried out further testing to prove the repair. The customer was happy to have the oven back up and running.
We can do so much with recycled parts and give electronic items a new lease on life.
Warning: Never work on the secondary side of the transformer without first making sure the high voltage capacitor is completely discharged. All high voltage capacitors on microwaves have got an in built discharge resistor but if the resistor goes open circuit then the capacitor will stay charged. For your information it is the amps that kill not volts, these caps in microwave can kill so beware.
You may also watch the video below on how to troubleshoot Microwaves Oven In Minutes:
This article was prepared for you by Mark Rabone from Australia.
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