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CD-ROM Samples

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Important   Microwave Oven Safety Precautions
Fully warranted used commercial microwaves for sale
© 1996-2012 J. Carlton Gallawa. All Rights Reserved Worldwide
Ukrainian Translation

Microwave Ovens Are Dangerous Appliances to Work On

Failure to carefully follow these safety guidelines could result in serious injury or death

The microwave oven is one of the most dangerous appliances to repair. The high-voltage potential combined with the high-current capability of an operating microwave oven pose a deadly threat to the reckless worker. In addition, microwave ovens are radiation-emitting devices. Normally this does not present a problem. However, improper replacement methods or tampering with safety systems could expose the unwary troubleshooter to dangerous levels of microwave leakage. Therefore, extreme caution and proper procedures MUST be used at all times. 

When diagnosing a microwave oven, many problems can be detected merely with careful observation, that is, with the power disconnected. Most tests can be accomplished with the power off and the oven unplugged. We suggest that you leave the "live" testing to the professionals. Nonetheless, certain safety habits must be developed and maintained. If you have experience in troubleshooting electrical equipment, some of these safety precautions may be familiar. However, the high-current potential of the high-voltage circuits in a microwave oven make them possibly life-saving steps. 

If you are uneasy or unsure about any of these safety procedures or warnings; or if you feel uncertain as to their importance or your ability to manage them, it would be in your best interest to leave the repair to a qualified professional.

  • FIRST and ALWAYS, before attempting any repairs, make certain that the unit is not plugged in. 
  • Before touching any components or wiring, ALWAYS DISCHARGE THE HIGH VOLTAGE CAPACITOR! The high voltage capacitor will quite normally maintain a painfully high-voltagecharge even after the oven is unplugged. Some capacitors employ a bleeder resistor (either externally or internally) that allows the charge to slowly bleed (or drain) off after the oven is unplugged. Do not trust a bleeder resistor—it may be open.
    If you forget to discharge the capacitor, your fingers may ultimately provide the discharge path. You only make this mistake a few times, because, while the electric shock is painful, the real punishment comes when you reflexively yank your hand out leaving behind layers of skin on razor-like edges that are there as a reminder to never again forget to discharge the high voltage capacitor.

How To Discharge The High Voltage Capacitor in Microwave Ovens

First Method: The capacitor is discharged by creating a short circuit (direct connection) between the two capacitor terminals and from each terminal to chassis ground (bare metal surface).

  1. Do this by touching the blade of an insulated-handled screw driver to one terminal, then slide it toward the other terminal until it makes contact and hold it there for a few seconds. (This can result in a rather startling "pop!")
  2. Repeat the procedure to create a short between each capacitor terminal and chassis ground.
  3. If the capacitor has three terminals, use the same procedure to create a short circuit between each terminal and then from each terminal to ground.
  4. Older Amana-made models (generally those manufactured before 1977) have red, round filter capacitors mounted in the base of the magnetron tube which can also hold a charge. Ground each magnetron terminal by creating a short circuit to chassis ground using the blade of a screwdriver as explained above.
When working on a microwave oven always discharge the high-voltage capacitor first
Although most manufacturers specify the above procedure in their service manuals, some prefer the following alternate method involving the use of a resistor to slow the discharge rate.

Alternate Method: As shown in the illustration to the right, attach one end of a 100K - 150K ohm, 25 watt resistor to the bare metal chassis with an alligator clip. Attach the other end of the resistor to the blade of a well insulated screwdriver.

  1. Touch the blade of the screwdriver to one of the capacitor terminals and hold it there for a few seconds. Then repeat the procedure for the other terminal.
  2. To ensure that the capacitor is fully discharged, follow the first method (shown above).
WARNING

Warning - Death on Contact
Never attempt to measure the High Voltage at the magnetron or transformer terminals.

high-voltage circuits of microwave ovens are extrememly dangerous
The high-voltage circuits in a microwave oven generate from 3000 to 5000 volts DC and higher! 

This high voltage combined with the potential for high current make the high-voltage circuits of a microwave oven extremely dangerous to work on or around when the oven is energized.

NEVER, under any circumstances, touch any oven components or wiring with your hand or even with an insulated tool during a cook operation.
LIVE TESTING It is better (and safer) to avoid making live tests if possible. If such tests become necessary, and if you are an experienced professional technician, the tests can be performed safely as follows:
  1. Make sure the oven is unplugged and that the capacitor discharged.
  2. Attach the meter leads to the prospective test points with insulated clip leads.
  3. Then step back, plug in the oven, perform the test and observe the meter.
  4. In addition, use only one hand whenever possible. Try putting the other hand behind your back or in your pocket. (Two hands could complete a circuit through your body. Use only one hand and/or an insulated tool, even when the unit is unplugged).

how to test for leakage from a microwave oven CHECKING FOR RF LEAKAGE After any adjustment or repair on a microwave oven, manufacturers require that a final microwave leakage check be performed to ensure that the unit does not emit excessive radiation.

  • If there is obvious damage to the door or door seal and/or if there is evidence that the unit has been previously tampered with by someone of questionable competence, be prepared with your leakage tester turned on before energizing the oven. There could be components that are improperly installed and thus possibly emitting dangerous levels of RF leakage.
  • Most amateurs, and many professionals, do not own an RF leakage meter. These meters are available at appliance and electronic parts suppliers, ranging in price from about $10.00 up to many hundreds of dollars for the certified models used at the professional level.
  • Inexpensive RF detection devices are also available at many retail stores.
    In lieu of purchasing a certified RF leak checker, you can take your repaired unit to a factory authorized servicer who will very likely check the leakage for free.
RF LEAKAGE TEST PROCEDURE If you conclude that a leakage test is necessary, click HERE for the procedure (this page is currently under construction and not active)

Additional Common-Sense Safety Guidelines for Working with Microwave Ovens

  • Do not work alone. Make sure another person is nearby in case of an emergency.
  • Use care when lifting and carrying a microwave oven. Remember, most of the weight is usually on one side (the control panel side).
    1. When lifting a microwave oven, keep your back straight and use your legs, not your back, to do the lifting.
    2. Before carrying, secure the power cord and insure a clear path to your destination.
    3. 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.
  • Remove your watch and other jewelry.
    1. Watches that are susceptible to magnetism will be damaged by the intense magnetic field surrounding the magnetron tube.
    2. Jewelry is electrically conductive and serious injury could result.
  • Wear rubber soled shoes.
  • Never defeat or tamper with the safety interlock switches or the fuse.
  • Do not touch printed circuit board components or circuitry unless you are properly grounded.
    1. Static electricity can damage certain static sensitive components.
  • Be aware that opening or otherwise modifying your equipment may void any manufacturer's warranty. 
If you fully understand these precautions and are prepared to carefully observe them, proceed to the Master Repair Database or The Microwave Oven Super Troubleshooter
If you are uneasy or unsure about any of these safety procedures, or feel uncertain as to their importance, it would probably be in your best interest to leave the repair to a qualified professional. 

 

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DOWNLOAD FREE SAMPLES FROM THE CD: The Complete Microwave Oven Service Handbook: Operation, Maintenance, Troubleshooting and Repair DOWNLOAD FREE SAMPLES FROM THE CD: The Complete Microwave Oven Service Handbook: Operation, Maintenance, Troubleshooting and Repair Previous Page Home Page Important Safety Information Contact Us About the Author Free Case History Database Free Microwave Oven Troubleshooting Guide DOWNLOAD FREE SAMPLES FROM THE CD: The Complete Microwave Oven Service Handbook: Operation, Maintenance, Troubleshooting and Repair

USE OF THIS SITE : Through your use of this Site, you certify that you have read, understood and agreed to the following TERMS OF USE, including the following disclaimer as well as the safety precautions outlined above.

TERMS OF USE: Through your use of this Site, you hereby acknowledge and agree that troubleshooting and repairing a microwave oven can be dangerous and can involve risk of serious injury and/or death and/or property damage. Further, you consciously and voluntarily assume all such risks, dangers and hazards inherent in these procedures and assume the same risks for any invitees including minor children or legal wards.

DISCLAIMER: The author and/or owner and/or administrator of this Site assumes no liability for any incidental, consequential or other liability from the use of this information. All risks and damages, incidental or otherwise, arising from the use or misuse of the information contained herein are entirely the responsibility of the user. Although careful precaution has been taken in the preparation of this material, we assume no responsibility for omissions or errors.

Copyright © Information: Unless otherwise noted, all materials at this cite (including without limitation all text, html markup, graphics, and graphic elements) are copyrighted © 1989-2012 by J. Carlton Gallawa. The material available through this site may be freely used for attributed noncommercial educational purposes only. We ask that due credit and notification be given the author. All materials appearing on this web site may not be reproduced, stored in any retrieval system, or used in any way for commercial purposes without the express prior written permission of the copyright holder. Send correspondence to: Microtech, P.O. Box 940, Gonzalez, Florida 32560

© 1989-2012 J. Carlton Gallawa . All Rights Reserved Worldwide

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