NOTE: This document replaces the previous text version document here: http://www.microwavecontrol.com/safety.txt 

MICROWAVE OVEN CRITICAL SAFETY WARNINGS
copyright 2004+ updated February 3, 2017
William E. Miller, AS-EET
http://www.MicrowaveControl.com How a Microwave Works

By utilizing information on this site, you agree to hold the owner harmless and blameless for any consequences arising from your decision to take apart or inspect your microwave oven. See the safety warnings linked below before you proceed.

Please see my safety and disassembly pages here:
http://www.microwavecontrol.com/safety.htm
http://www.microwavecontrol.com/disassembly.htm 

I offer these safety warnings, some of which may appear repeatedly in this document for clarity.

MICROWAVE OVENS UTILIZE AND PRODUCE DEADLY VOLTAGES WHICH CAN BE INSTANTLY LETHAL!

Always be totally sure the microwave oven is unplugged from the wall (disconnected from power line) before attempting any disassembly.

POWER LINE VOLTAGE

Power line voltage can be instantly lethal.

Always be completely sure the microwave oven is totally unplugged from the wall (disconnected from power line) before attempting any disassembly.

If you are ever in the presence of a microwave oven (or other appliance) which has its cover removed but is still connected to the power line:

- do not touch any component inside the appliance (even with an insulated tool)

- wear non-conductive or rubber-soled shoes

- be sure you, your shoes and clothing, and the immediate area are all dry

HIGH VOLTAGE AT HIGH FREQUENCY

Microwave ovens produce and store high voltages which vary from about 3,000 to 5,000 volts. These voltages can cause heart failure, heart defibrillation, and/or extensive injury, any of which can be instantly or eventually fatal.

If you are ever working in the presence of a microwave oven (or other appliance) which has its cover removed but is still connected to the power line:

- do not touch any component inside the appliance

- wear non-conductive or rubber-soled shoes

"Live" testing while the oven is running is NOT recommended for anyone who does not have proper training and experience.

Always discharge the high voltage capacitor before touching any components or wiring in the high voltage section of the unplugged microwave. (details below)

MICROWAVE "RADIATION"

Microwave ovens produce non-ionizing microwave energy which is similar to radio waves and light. While it is not the ionizing type of "radiation" that is known to cause cellular mutation and therefore doesn't cause cancer, microwave energy can cause serious burns and injury or a fire.

Never attempt to bypass "jumper across" or otherwise defeat any safety device such as door switches in a microwave oven. The switches are basically designed to prevent the oven from running when the door is open.

Never attempt to power or operate a microwave that has a damaged, misaligned, or removed door or door panel or part.

Never leave a microwave running unattended, which can result sin a house fire.

SHARP EDGES

Microwave ovens are made of sheet metal and other parts that have very sharp edges and corners that can cause very serious cuts. This is the real risk when working on an oven an touching a charged high voltage capacitor.

Such cuts and slashes often occur when a person experiences a shock, etc. from the microwave oven, then reflexively pulls back his hand or arm.

It is recommended that you remove any watches or jewelry when working on or near appliances, since they can get caught inside, posing a serious safety hazard.

HEAVY MAGNET WARNING

Microwave ovens contain a device called a magnetron, which contains a very large and powerful magnet.

This large magnet can disrupt or seriously damage watches and pacemakers.

STATIC ELECTRICITY

The components on the printed circuit board are static-sensitive devices and can be damaged by static electricity, even if you do not feel a discharge.

While this is not always an issue on a board assembly, it is still best not to touch these components or the control panel without properly discharging yourself first.

This can be done by touching or maintaining contact with the metal chassis or screw of a properly grounded appliance.

But NEVER do this if the appliance that is apart is still connected to the power line.

DISCHARGING HIGH VOLTAGE CAPACITORS

A microwave oven's high-voltage capacitor is used to produce final high-voltage.

While it does have a "bleeder resistor" designed to drain the high voltage charge after cooking stops, anything can fail, so it's safer to discharge the high-voltage capacitor to prevent an electric shock.

Always be totally sure the microwave oven is unplugged from the wall (disconnected from power line) before attempting any disassembly.

It's a good idea to wait a few minutes after unplugging the oven before discharging the capacitor.

When you discharge the capacitor, a loud pop may result. It is not harmful. Just be aware that it may happen, so you are prepared for it and a reflex reaction does not cause you to be injured.

You must use an insulated tool such as a screwdriver. Be sure the handle is plastic or has a rubber sleeve. Never use a wooden handled screwdriver, as the wood can absorb moisture and conduct, giving you a shock.

Be sure your hand and the tool are clean and dry.

If you have a dry rubber glove with no tears or holes, that would help prevent contact with the stored charge, too.

Refer to this photo to identify the capacitor:
http://031d26d.namesecurehost.com/mwc/discharge.jpg

Discharge procedure:

1. Touch the blade of the screwdriver to one of the terminals of the high-voltage capacitor, then slide it against the other terminal and hold it for a second or two. If you're going to hear a pop, it's when the two terminals get shorted.

2. Touch the blade of the screwdriver to one of the terminals of the high-voltage capacitor, then slide it against the metal of either the case of the capacitor or the back panel of the microwave.

3. Touch the blade of the screwdriver to the other terminal of the high-voltage capacitor, then slide it against the metal of either the case of the capacitor or the back panel of the microwave.

Some microwaves made before the 1980s may have a capacitor built in to the magnetron, but I do not recommend servicing these ovens at all because of part availability and efficiency issues, as well as aging of electrolytic capacitors which can cause unpredictable behavior in electronics.

ORDERING MICROWAVE OVEN PARTS

See my parts page at http://microwavecontrol.com/parts.htm.

MORE QUESTIONS?

Please visit my Web site and e-mail me. It's best to e-mail instead of calling, because that way I can e-mail you pictures, links, and files as needed.

See http://www.MicrowaveControl.com.

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