© 1998-2013 J. Carlton Gallawa
All Rights Reserved Worldwide
Last updated 1/2012
Learn the nuts and volts of microwave oven and VCR repair

This page includes case histories of the brands:

Panasonic to Quasar

Page 2

Instructions On How To Use This Information For Troubleshooting and Repairing Microwave Ovens

  1. After reading the safety precautions , find the brand and model number, or the number closest to the model you are repairing.
  2. Find the symptom(s) that most closely match the symptom(s) being displayed by the oven you are repairing.
  3. Follow the specific troubleshooting and/or repair instructions to complete the repair. Click on highlighted text for a detailed explanation of that procedure.
  4. Since this database is constantly being updated and appended, if you don't find what your looking for, try again at a later time.
  5. Click here    if you would like to be notified by e-mail when this page is updated.
Please Note:
We hope that you find the information here helpful.. .

  Important Safety Information

Repairing a microwave oven is a dangerous task. For your personal safety, please do not proceed unless you fully understand and are prepared to follow carefully these appropriate safety precautions .

Disclaimer: The author 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.

© 1996-2013 J. Carlton Gallawa
All Rights Reserved Worldwide
© Copyright Information


Model: NN-6371WM
Symptom: Stopped working after lightning storm
Problem: Built-in surge protection on printed circuit board has opened. This circuit consists of a fine foil pattern (or filter coil - depending on the model) that acts to fuse the primary side of the low-voltage transformer.
Solution: Rebuild the surge protection circuit. Replace the varistor
Procedure: Foil Pattern/Filter Coil Repair Procedure
Model: NN-6653A
Symptom: No heat, and making a low humming sound
Problem: Shorted high voltage diode (rectifier)
Test: High-Voltage Diode (Rectifier) Test
Solution: Replace diode (rectifier), part # A62024000AP
Model: NN-9507
Symptom: Convection cooking mode does not work
Problem: Defective heater fan motor
Solution: Replace heater fan motor. Part # A41794210AP. Price:$30.92
Model: MW-1040, MW-9405
Symptom: Stopped heating
Problem: Magnetron filament connectors have loosened and, due to resistive heat, the terminal connections have deteriorated and burned off.
Solution: Repair defective terminals as follows:Either (1) Cut away burned wire, clean the magnetron terminals, and replace the slip-on connectors, or (2) Cut away burned wire and connector(s). Clean terminals to prepare for soldering. Solder filament leads directly to magnetron terminals. Be careful not to apply soldering heat any longer than necessary
Model: MQ-6620TW
Symptom: Humming sound coming from the control panel.
Problem: Open capacitor on printed circuit board
Solution: Replace open capacitor:C33, 35v 2200uf
Model: MQ-7700RW, MQ-7757BW, MQ-8768W, MQ-8798H, MQ-8877BW, MQS-1403W
Symptom: No heat. Or, oven counts down but nothing else. Or, starts, then immediately stops
Problem: The slip-on connectors on the upper and/or lower interlock switch have burned loose, possibly damaging the switch.
Test: Interlock Switch Test
Solution: Repair the burned connections by either replacing the slip-on connector(s) or soldering the wire(s) directly to the switch.
Note: If the switch terminal was severely burned, the switch should also be replaced, even if it appears to work normally.
Note: Generic micro-switches rated at 15 or 16 amps with appropriate terminal configuration are available at appliance parts suppliers.
Model: MQS-1106W
Symptom: "Started," then popped and went dead.
Problem: Shorted high voltage capacitor has caused fuse to blow.
Test: High-Voltage Capacitor Test
Solution: Replace shorted 1 Mfd, 2100 VAC capacitor. Install new line fuse.
Model: MQS-1403W
Symptom: No heat
Problem: Shorted high voltage diode (rectifier)
Test: High-Voltage Diode (Rectifier) Test
Solution: Replace diode (rectifier). Suitable generic replacements are available at appliance parts suppliers.
End section P to Q
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Parts Suppliers and Manufacturer Contacts

You can contact these parts suppliers and microwave oven equipment manufacturers directly for replacement parts, product literature, dealer locations, technical assistance, etc. Please e-mail additions or corrections to: j.gallawa@cox.net
Glossary of Electronic and Microwave Oven Related Terms 
Let us know what you think, or submit your own repair tip j.gallawa@cox.net 
microwave oven repair selection keypad
hands-on repair Are you ready to get into the repair business? Microtech's fantastic new CD-ROM tells you ALL about repairing commercial and residential microwave ovens. The course was originally developed for colleges and trade schools. But since its release, scores of technically-minded individuals, from amateur to seasoned pro, have quickly recognized it as a valuable training tool and profitable reference guide. Here are fully tested, self-teaching guidelines for disassembling, successfully diagnosing, and safely repairing all types of microwave ovens. We invite you to check it out...
Operation, Maintenance, Troubleshooting and Repair

Copyright © 1989-2013 by J. Carlton Gallawa
Learn everything you need to know about repairing commercial and residential microwave ovens
Microtech Home Page Important Safety Instructions Samsung through Whirlpool Panasonic through Quasar Kenmore (Sears) through Montgomery Wards Amana through JCPenney
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