Question about Microwave Ovens

1 Answer

GE Spacemaker Microwave Blown Fuse replaced still no power

Obviously blown ceramic 20AMP fuse. Replaced fuse. Still no lights no power. Technical data sheet indicates Varistor replacement or failed power supply. Know where I can get a TVR 14271 (varistor)? I have researched this for hours and read somewhere that if I cut out the Varistor that took the power hit, plug everything back in and it works then I will have confirmed Varistor failure and the Microwave will run without surge protection until I replace the Varistor. I would feel more comfortable having the replacement in-hand before snipping it out. Advice?
History: Microwave shares circuit with other appliances. Has tripped the breaker about a dozen times since we moved into this place last year. Manual advises Microwave be on it's own "120Volt, 15-20 Amp. parallel, grounded separate circuit." This is not the case.

Posted by on

  • 3 more comments 
  • Bastion Jul 21, 2008

    Thank you for your response! The Microwave is a GE SpaceMaker JVM1640BJ03. My original problem was no lights and no power (apparently) coming into the microwave. I checked the house circuit breaker as usual and reset it.I expected the Microwave to start working again as usual, but no lights no power. I took it aparta nd swapped out the blown fuse on the Microwave and I still have no lights an no power. The Varistor doesn't appear cracked or split. I used my $7 Digital Multimiter to test. Set it to 200 ohms and it jumps all over the place from 2.0 on up to 188. I don't know what this means. When I set it to 2000 ohms it jumps all over but always centers back on 300.

    Thanks for your help!

  • Bastion Jul 28, 2008

    Hello again,

    It's a JVM1640BJ03 (I was waylaid by a plumbing issue). Thanks for the heads-up on the breaker.

    Looks like I get to remove the microwave form the wall and see my first TCO :-). From the mini Manual "Oven must be removed from wall. Remove outer case to access part.

    I'll let you know how it works out.

    Thanks Again

  • Bastion Jul 29, 2008

    Disassembled and tested all 4 thermostats or TCO's. The "cavity TCO" doesn't get a reading on the meter, but the others do read Zero. Found it online shipped for $16 and change. Part Number: WB27X10714 THERMOSTAT(DUCT) US $9.53

  • Bastion Aug 08, 2008

    Part arrived today via the slow boat shipping I chose. Swapped it out, plugged it in and Viola! All better.

    Thank you so much for you invaluable assistance! Fixed!

  • rebarnz Mar 21, 2009

    Very helpful response MicrowaveSvc! I probably couln't have done the troubleshooting without your advice, but I had the same problem (total power cutout), and it was indeed my "cavity TCO" that was bad. Ordered new part, istalled, and all is well.
    Thanks very much for this advice.

    My oven is actually a JVM1660 , but the phenomenon is the same. The internal fuse never blew on mine - just the TCO.

×

1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    Superstar:

    An expert that got 20 achievements.

    All-Star:

    An expert that got 10 achievements.

    MVP:

    An expert that got 5 achievements.

  • Microwave Ovens Master
  • 8,820 Answers

If you measure across the varistor leads with it still in the circuit, you should measure around 100-300 ohms, which is the DC resistance of the primary of the low voltage transformer.

If you read infinity / open the primary of the low voltage transformer is bad.

If the varistor is bad, it will be shorted and usually it will be cracked or split. This is a much simpler way to test the varistor.

Have you checked the magnetron thermal cutout (TCO) (or thermostat if so equipped) and the oven TCO? These are the leading causes of a dead GE when the fuse is okay.

You didn't mention the model number. What is it?

Please reply back here if you still need help.

We're happy to help you. Once we have all your information and offer a final solution, we'd appreciate your thoughtful rating of our answer.

Posted on Jul 18, 2008

  • William Miller
    William Miller Jul 21, 2008

    The jumping around of the meter is probably due to the coating on the varistor, and your leads are not making good contact.



    But the fact that it settles around 200-300 ohms means it's not shorted, and your transformer primary is almost certainly okay.



    You mention that the breaker has tripped a dozen times in a year? A breaker can only trip so many times before it is weakend and compromised. It should be replaced after so manny trips. I would consult an electrician for that number, or check the packaging on a new breraker.



    Have you checked the magnetron thermal cutout (TCO) (or thermostat if so equipped) and the oven TCO? These are the leading causes of a dead GE when the fuse is okay.



    You can usually find helpful exploded view diagrams and order parts by entering your full model number here.



    The "mini-manual" will also show the thermostats and/or TCOs.



    I'd say that's the problem.



    We're happy to help you and we'd appreciate your thoughtful rating of our answer.

×

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

The fuse inside was blown and on opening found the blown fuse broken. replaced it and it is working. however the blown fuse was smaller in size while we replaced with a bigger size. does it matter???


you must replace the FUSE with the same capacity for example: you will see in the metal fuse the incription 240vac-15amp see if the fuse is Ceramic or Glass, you CAN not use 125vac,10amp or 20amp, the circuit WILL not protect the electronic system, and will dammed another section. Please rectify this INMEDIATELY.
God bless you

Jul 31, 2012 | Microwave Ovens

1 Answer

When I turn on the microwave for cooking, a fuse 20amp burnt, then i replaced the fuse and set it for cooking and the fuse 20amp. burnt again,


okay this means that your microwave is having a short problem check the varistor across the primary winding of the low voltage transformer probably it is burnt that cause it to short or it is shorted without sign..cut away varistor from the connection and put in a fuss then see what it does.good luck.

Sep 13, 2011 | Microwave Ovens

1 Answer

Fuse size for sharp mircowave r 520ks


The fuse will be a 20amp ceramic. The fuse should be available at hardware stores, Radio Shack.
If the fuse is blown, there is a very good chance you have another problem, possibly a bad or misaligned door switch, shorted capacitor. Replace the fuse, if it blows again you will have to figure out why. Door switches are the most common reason for the fuse to blow.

Feb 02, 2011 | Sharp R-520KS Microwave Oven

1 Answer

Came in today; our spacemaker ge microwave xl 1400 would not light up, turn table would not turn, no date or time or anything registering on panel


  1. Check the circuit breaker.
  2. Verify that the outlet to oven has power (plug in a trouble light or other small device).
  3. If you have power there, take the oven off the wall, remove the top cover and check whether you have power at the controller board. (If you don't know where to put the voltmeter leads, take the oven to an appliance tech to perform these tests.) If you power at the low voltage transformer, the board has failed.
  4. If not, check the three thermal cutouts and the fuse. One thermal cutout is located on top of the oven, most likely under the light bulb cover. The next is fastened to the magnetron, and the last is down near the bottom just behind the controller module. If any of these is open, the oven will not work. If the fuse is blown, look for a short circuit before replacing it (check the varistor on the controller board first). The varistor is listed as a separate repair part; don't get soaked for a controller board if this is bad.

Jan 17, 2011 | GE Spacemaker JVM1640SJ Microwave Oven

1 Answer

How do I get to the fuse for replacement?


remove panel that's over the door (screws on top). next, remove control panel by unscrewing usually 1 screw on top of panel. finally, lift panel upward; then pull foward. of course, unplug power cord before disassembly. fuse should be 20amp 3ab20 ceramic snap-in fuse and is located inside up high near cooling fan. fuse can be obtained at radio shack. keep in mind fuses fail for a reason.

Aug 23, 2010 | GE JVM1870 Microwave Oven

1 Answer

While cooking it just quit. Checked circuit breaker & was ok. I have no schematic of the inside so I haven't taken apart yet to see if there may be an inside fuse.


There is usually a 125V, 20 AMP line fuse inside the microwave, mounted at the point where the power cord enters the back of the unit. Or, on a line filter control power. Unfortunately, you will need to uninstall the oven (if this is an over the range model), UNPLUG it and remove the exterior case to access. The case comes off in various ways depending on manufacture and model. Since you provided no model number, I can only give this basic advice.

If the line fuse is blown, you can usually purchase a box of fuses at a hardware store for just a little more than what the manufacturer charges for a single fuse. 125V, 20AMP Ceramic Slow Blow fuses are recommended.

If you have any questions, or need additional assistance troubleshooting, please post back with your MODEL NUMBER and let me know. I hope you find this information helpful.

NOTE: Make sure you take any resistance readings with the microwave UNPLUGGED and the component under test isolated (removed) from the circuit. These ovens can blow a fuse by simply sitting idle. This can occur from any power fluctuations, brown outs, voltage spikes, etc. Or, it could be the symptom of a component that may have failed. If you find the internal fuse blown and replace it, only to have it blow again, you have a more significant problem than a simple blown fuse.

Aug 12, 2010 | Kenmore Microwave Ovens

1 Answer

This model just stopped working while heating food up. Now cannot get even the power to register when you plug it in. Is this doen for?


There is usually a 125V, 20 AMP line fuse inside the microwave, mounted at the point where the power cord enters the back of the unit. Unfortunately, you will need to uninstall the oven (if this is an over the range model), UNPLUG it and remove the exterior case to access. The case comes off in various ways depending on manufacture and model. If the model number you listed this question under is correct, the line fuse is connected in line with the power cord inside the unit and is listed as part of item 4 in the parts listing (part number STD384200).

If the line fuse is blown, you can usually purchase a box of fuses at a hardware store for just a little more than what the manufacturer charges for a single fuse. 125V, 20AMP Ceramic Slow Blow fuses are recommended.

If you have any questions, or need additional assistance troubleshooting, please post back and let me know. I hope you find this information helpful.

NOTE: Make sure you take any resistance readings with the microwave UNPLUGGED and the component under test isolated (removed) from the circuit. These ovens can blow a fuse by simply sitting idle. This can occur from any power fluctuations, brown outs, voltage spikes, etc. Or, it could be the symptom of a component that may have failed. If you find the internal fuse blown and replace it, only to have it blow again, you have a more significant problem than a simple blown fuse.

Jul 22, 2010 | Emerson MW8102SS 1100 Watts Microwave Oven

1 Answer

Microwave oven blowing 20 amp ceramic fuse


Chances are if the varistor fails, it fails drastically causing a short circuit across the supply. It will sit across the supply (it will look like a thick ceramic capacitor) and you can check for continuity after isolating that at one end. If it shows low resistance (it should show almost open circuit with a Digital meter), replace it.

It need not be the culprit. If you are familiar working with High voltage circuits ( they are lethal inside a microwave ovens as the current capability is high here), you can discharge the doubler capacitor and isolate the high voltage diode to check for shorts in the HT area.

Mar 18, 2009 | Microwave Ovens

3 Answers

Panasonic Microwave oven - cooking operation stops afer 2 seconds


Sounds like a short in the microwave circuit. One or more of the following four components has failed -

Transformer
Magnetron
Diode
Capacitor

Repair is not for the amateur, unless you know how to take things apart, and put them back together EXACTLY as the were found.

Parts are available on the Net, and you can get the P/N's off the old components to identify suppliers of the new ones.

Don't try and measure resistance of the diode. It's impedance is far too high to get a good reading. They're cheap anyway. Always replace the capacitor, they're cheap too. No way to test the magnetron, and the transformer is not easy to test either.

Jan 16, 2009 | Panasonic NN-S952 Microwave Oven

Not finding what you are looking for?
Microwave Ovens Logo

Related Topics:

1,700 people viewed this question

Ask a Question

Usually answered in minutes!

Top Microwave Ovens Experts

William Miller
William Miller

Level 3 Expert

8820 Answers

Donald DCruz
Donald DCruz

Level 3 Expert

17129 Answers

Devabhakthuni...
Devabhakthuni...

Level 2 Expert

224 Answers

Are you a Microwave Oven Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...