Inner Workings of Microwaves

**NOTICE**
Due to the danger and complexity of electronic equipment repair, the following technical tip is intended for professional reference only. Please refer to manufacturer’s recommendations as Encompass does not guarantee the accuracy, reliability or safety of this information. 

Although microwave ovens vary in design, they are virtually all similar in function. Most models are equipped with preset cooking times, programmed according to the basic popularity of certain food items, such as popcorn. Microwaves also have power level setting and timing options for food items not included in the pre-set modules.

After the desired cooking setting has been chosen and the start button pressed, the control board sends 120 volts of electricity traveling through a series of components inside your microwave and converts it into high-powered radio waves that cook your food. Once the radio waves are inside the cooking area, they penetrate the food from the outside in causing moisture in the food to vibrate intensely. It is this vibration that generates the heat that cooks the food.

Models equipped with a motorized turntable, rotate food so that radio waves can cook the food uniformly. For more, watch this  5-minute video for a deeper understanding of how a microwave oven works. Here are some tips to deal with operational issues:

How to Remove and Replace the Magnetron in a Microwave Not Heating
If your microwave fails to warm or cook your food, it’s possible that the magnetron will need to be replaced. Due to the electrical danger involved, it’s recommended that this service be performed by a professional appliance repair company; here are the repair basics:

Tools Needed

• Two insulated screwdrivers
• Needle nose pliers
• # 20 Torx screwdriver
• Phillips screwdriver

The following procedure is for a Whirlpool microwave that sits above the range. Servicing will take some time and patience to complete. Several screws must be removed to access the magnetron. Place the screws in a container to avoid misplacement and then:

• Remove turntable and set aside.
• Using Phillips bit with electrical drill, dismount microwave by removing two screws that hold it to kitchen cabinet.
• Tilt microwave toward you at about 45-degree angle and lift it off rear bracket that holds it in place on kitchen wall.
• Remove grill and set aside.
• Flip microwave on its back and remove eight Phillips-style screws. When completed, flip microwave back to its original position.
• Remove 10 Phillips screws that hold microwave wrap in place. Remove rear cover and set aside.
• Now remove eight more screws from top of microwave cover.
• Don’t forget to remove two screws that hold blower cover in place. Remove cover and set aside.
• With all exterior screws removed, you should be able to grab sides of cover and gently pull toward yourself, lift it from its place and set aside.
• Remove panel that protects diode and capacitor.
• Since capacitor retains residual voltage that could result in serious shock, you are going to short out remaining electricity.
• Place metal end of one insulated screwdriver on one capacitor terminal and place  other insulated screwdriver on other tab. Cross screwdrivers and hold them together, metal to metal. You should hear pop or see spark discharging any
  remaining voltage in capacitor. To be safe, perform this task twice. After discharging residual voltage, and with microwave unplugged, it should be safe to proceed with removing magnetron.
• Access magnetron by removing three Phillips type screws that hold waveguide to rear panel. The waveguide is a plastic tube-like guide that directs radio waves to inside of microwave.
• Before removing waveguide, remove power cord ground wire from rear panel.
• Remove power cord by sliding it out of its guide and set aside to keep out of the way.
• Remove last screw holding waveguide in place and carefully manipulate waveguide from its place and set aside. There is one more part to remove before you can access magnetron.
• Remove magnetron thermostat, which is held in place with two Phillips screws. Gently pull thermostat away from magnetron.
• Use needle nose pliers to disconnect locking tabs from magnetron. Pinch tabs inward until you feel release and pull wire away from  tab. It does not matter in what order these wire tabs are reconnected to new magnetron; they are just
  completing a circuit.
• Use #20 Torx screwdriver to remove four screws that hold magnetron in position. Lift old magnetron from its location and set aside. You are now ready to install new magnetron and return microwave to its previous state. You are going to pretty much do everything in reverse order, but following is a quick go-to guide that will help ensure you reassemble all parts and screws to their previous locations. It is no good to finally get the microwave back together only to discover the blower fan cover was not reinstalled, or worst yet, the waveguide.
  ● Install the new magnetron (two torx screws).
  ● Reconnect wire tabs.
  ● Return magnetron thermostat to proper location (two Phillips screws).
  ● Reinstall waveguide cover (three Phillips screws).
  ● Slide power cord into its guide.
  ● Reconnect power cord ground wire to rear panel.
  ● Reinstall high voltage protective cover (two Phillips screws).
  ● Reinstall cover, and don’t forget to feed power cord through fan opening.
  ● Ensure cover is flush with panel by placing slide into panel and ensure no gaps exist on either side.
  ● Reinstall back screws first to keep cover in place.
  ● Replace fan cover, making sure to slide tabs into designated slots.
  ● Reinstall all screws in top panels.
  ● Flip microwave on its back and reinstall the eight Phillips screws.
  ● Flip upright and replace grill, ensuring tabs line up to designated slots. Once grill is in place, use two Phillips screws to  secure. Do not over tighten any screw used to hold plastic part in place as plastic could crack or break.
  ● Enlist help to hold and balance microwave as you line it up with bracket that holds unit to wall.
  ● Feed power cord through designated hole in kitchen cabinet.
  ● Reinstall the two Phillips screws that anchor top of microwave to bottom of  kitchen cabinet.

Special thanks to Fred’s Appliance Academy for this helpful tip!