DIY Appliance Repair: Safety Precautions to Take When Working on Microwave Ovens

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Of all the appliance found in the average home, the microwave oven is the dangerous for the DIY electrician to troubleshoot and repair. The magnetron, the power source for the microwave oven operates at extreme high voltage, 4,000 to 5,000 volts DC is not

With the cost of microwave ovens dropping every day, it really does not pay to have a professional appliance technician repair them. Most home microwaves sell for less than $100 and the minimum labor charge that most technicians will charge is $50 to $75 and that is a lot of money when repairs are completed in 15 minutes or less by replacing a blown fuse or thermal protector. You can make those repairs yourself in safety if you follow these safety rules when working on a microwave oven.

General safety rules.

Besides observing the same safety rules that you would observe when working on electrical device, always discharge the high-voltage oil-filled filter capacitor as soon as you remove the ovens case. Discharge the capacitor before touching any components inside the microwave oven. Many people simply short out the terminals on the capacitor using a screwdriver—do not do that. The high current surge and rapid discharge can destroy a perfectly good capacitor. Besides the possibility of destroying the capacitor, the tip of the screwdriver may weld itself to the capacitor's terminals. There are tools available for safely discharging the high-voltage capacitor, but you can build one of your own using an old screwdriver, a resistor, a short length of wire and two alligator clips. This drawing shows you how to make one in a couple of minutes.

You will need the following tools and supplies:

  • 6 Inch screwdriver with all plastic or all wood handle

  • 2 Alligator clips

  • 18 Inch length of #14 stranded copper wire

  • Wire cutters

  • Wire strippers

  • soldering iron/gun

  • Rosin core solder

Construct as shown in the drawing.

Common sense safety rules to follow.

  • Always have someone in the shop with you when you are working on a microwave oven. No matter how careful you are, emergencies can happen.

  • Use care when lifting and carrying a microwave oven. Remember, most of the weight is usually on one side (the control panel side).

    • When lifting a microwave oven, keep your back straight and use your legs, not your back, to do the lifting.

    • Before carrying, secure the power cord and insure a clear path to your destination.

    • When lifting an oven in or out of an automobile, lift it on to the seat--do not slide it. Better yet, place a piece of cardboard on the seat first.

  • Do not wear watches or any jewelry on your hands when working on any electrical device.

  • Always wear rubber soled shoes or stand on a rubber mat.

  • When ever possible, work with one hand in your pocket.

  • Never touch the printed circuit boards or any of the components on them unless you are wearing a static grounding wrist band. Static electricity can destroy sensitive solid state components.

  • Never disable or bypass any of the safety interlocks or switches. If one is defective, replace it, do not bypass it.

How to use the capacitor discharging tool.

  • Attach one alligator clip to the shaft of the screwdriver.

  • Attach the other alligator clip to the metal lip on the capacitor, being careful not to touch or come with ½ Inches of any of the terminal with your fingers or hand. Depending on the condition of the capacitor and the charge on it, it can easily span a 3/8-inch air gap to shock you.

  • Touch the blade of the screwdriver to each of the terminals on the capacitor, holding the contact for at least 10 to 20 seconds each.

Now the microwave oven is safe for you to work on.


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