My microwave oven stopped working. If throw it away, the world will have one more trash and I will have to spend some more money to bring back a new one. I decided to open the microwave oven to see if I can save it.
The following steps are what I did. Finally, I fixed it and the cost is only $3.50.
Warning: 1) Read and Follow the warning label on the microwave oven. 2) Never open back cover on power plug in. 3) Capacitor must be discharged before beginning any repair (In my case, the step is not include, see step 8).
Step 1: Unplug Power and Remove Moving Parts
Be sure the power cord is unplugged and then remove the moving parts from microwave oven.
Step 2: Open the Back Cover
There are 2 screws on right side and 1 screw on left side. They can be easily remove with normal screwdriver. But there are 4 screws on the back are little special, a star screwdriver is needed.
Step 3: Check the Fuse First
After open the back cover, check the fuse first. I checked it with a resistor tester, if it shows the fuse resistance value is infinity. That means the fuse is broken. Only need to change a fuse for the microwave oven. But it showed a resistance value on the meter, this means the fuse is not broken. I have to go to find problem in some other places.
Step 4: Inspect Door Switches
The next step is to inspect door switches. There are 3 switches in the microwave oven. See their location in the pictures. Press down the pin beside the switch and rotate the switch a little to take it out. Inspect one by one, I found one switch is little different with others, the first is press the button there is no contacts click voice, the second, found there is something burned on the plastic by visual inspection.
Step 5: See Inside of the Switch
Open this switch to verify. In the picture, press the button down, the contacts cannot be connected. Yes, this one is broken. Since some plastic is burned, this switch has to be changed.
Step 6: Buy a Replacement Part
Found the spec and model on the back of the switch, I bought a similar switch online - the grey one on the picture, to replace the broken switch. Its cost is $3.50.
Step 7: Install the New Switch
The following things are connect wires to the new switch and install it properly. Just reverse the operation what I did. Close the back cover, drive in all screws and put the moving parts back.
Plug in power to test, the microwave oven works very well.
Step 8: About Discharge Capacitor
In my case, since the microwave oven has stopped working and unplugged power for a long time and there is one discharge resistor in the circuit, so I didn't show the discharge steps. I agree with the comments of instructablers. The capacitor must be discharged before beginning any repair.
The capacitor is in the back side lower corner. In my oven, it is covered by a plastic sheet. Please check it online how to discharge a capacitor.