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LG MS-2143RSL MICROWAVE OVENT NO HEAT

I have an LG MS-2143 RSL that can´t heat, 117VAC to the primary of the transformer and 3 VAC across the filament taps, resistance 0.47 Ohms across the magnetron terminals and 205Kohms from each terminal to ground. HV transformer primary winding 0.7 ohms, secondary winding 93 ohms, filament winding 0.7 ohms, diode 44Mohms/infinity. The ohmeter go up and down switching the leads back and forth across the capacitor terminas stoping in 10.107 Mohms, the capacitor has a 10 Mohms internal resistance. Energizing the transformer while the magnetron is disconnected results in the capacitor NO holding the charge, I confused I don´t know if the the problem are the capacitor or the magnetron

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Hi i am suggesting that it is probably the magy as the res to grndis a bit low and therefore loading the sec supply down , just a thought
cheers grant

Posted on Oct 23, 2008

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Microwave not heating up?


If it seems like it is running normally, but does not heat, here's a short list of possible culprits:

1. High voltage rectifier
2. Magnetron
3. High voltage capacitor
4. High voltage transformer
5. Magnetron thermal cutout

Problem could also be in the 117 vac supply to the h v transformer.

May 08, 2016 | Microwave Ovens

2 Answers

Micro wont heat. fix or replace? what could be the prob?


Sorry to read about your problem, I hope this helps you out.

Here are some problems you can have
  1. Blown fuse in HV transformer primary circuit or HV fuse (if used).
  2. Bad connections (particularly to magnetron filament).
  3. Open thermal protector or thermal fuse.
  4. Open HV capacitor, HV diode, HV transformer, or magnetron filament.
  5. Shorted HV diode, HV capacitor (will blow a fuse), or magnetron.
  6. Damaged protective VDR from filament to chassis (not commonly used).
  7. Defective HV relay (not commonly used).
Microwaves must be serviced by technicians due to the inherent dangers involved in repairing these appliances. Internal capacitors can retain a lethal electrical charge even though the unit is completely unplugged. A microwave radiation leakage test must be performed on the unit following any internal component repair.

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Jan 05, 2011 | Kenmore 63792 Microwave Oven

2 Answers

It will run but it won't heat. It also makes a funny "humming" sound and smells like burning plastic.


Sorry to read about your problem, I hope this helps you out.
you may one of these issues.
  1. Blown fuse in HV transformer primary circuit or HV fuse (if used).
  2. Bad connections (particularly to magnetron filament).
  3. Open thermal protector or thermal fuse.
  4. Open HV capacitor, HV diode, HV transformer, or magnetron filament.
  5. Shorted HV diode, HV capacitor (will blow a fuse), or magnetron.
  6. Damaged protective VDR from filament to chassis (not commonly used).
  7. Defective HV relay (not commonly used).
Microwaves must be serviced by technicians due to the inherent dangers involved in repairing these appliances. Internal capacitors can retain a lethal electrical charge even though the unit is completely unplugged. A microwave radiation leakage test must be performed on the unit following any internal component repair.

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Jan 04, 2011 | Maytag MMV5156AAS Microwave Oven

1 Answer

Microwave activate but will not heat food all light and buttons work but will not heat up


Sorry to read about your problem, I hope this helps you out.

You can many different issue's
  1. Blown fuse in HV transformer primary circuit or HV fuse (if used).
  2. Bad connections (particularly to magnetron filament).
  3. Open thermal protector or thermal fuse.
  4. Open HV capacitor, HV diode, HV transformer, or magnetron filament.
  5. Shorted HV diode, HV capacitor (will blow a fuse), or magnetron.
  6. Damaged protective VDR from filament to chassis (not commonly used).
  7. Defective HV relay (not commonly used).
Microwaves must be serviced by technicians due to the inherent dangers involved in repairing these appliances. Internal capacitors can retain a lethal electrical charge even though the unit is completely unplugged. A microwave radiation leakage test must be performed on the unit following any internal component repair.

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Jan 04, 2011 | GE Spacemaker JVM1640SJ Microwave Oven

1 Answer

GE JVM1440 will not heat.


Sorry to read about your problem, I hope this helps you out.

No heat but otherwise normal operation.
Possible causes:
  1. Blown fuse in HV transformer primary circuit or HV fuse (if used).
  2. Bad connections (particularly to magnetron filament).
  3. Open thermal protector or thermal fuse.
  4. Open HV capacitor, HV diode, HV transformer, or magnetron filament.
  5. Shorted HV diode, HV capacitor (will blow a fuse), or magnetron.
  6. Damaged protective VDR from filament to chassis (not commonly used).
  7. Defective HV relay (not commonly used)
Microwaves must be serviced by technicians due to the inherent dangers involved in repairing these appliances. Internal capacitors can retain a lethal electrical charge even though the unit is completely unplugged. A microwave radiation leakage test must be performed on the unit following any internal component repair.

I tried to help you. Please help me and Rate/Vote on my response. We take the time to answer your question. take the time to rate us.Thanks and good luck

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Jan 01, 2011 | GE JVM1440 Microwave Oven

1 Answer

Model 721.64282 microwave/convection oven - microwave not heating and making a loud noise. convection oven works


No heat but otherwise normal operationA shorted HV diode, magnetron, or certain parts of the HV wiring would probably result in a loud hum from the HV transformer but will likely not blow the main fuse. (However, the HV fuse - not present on most domestic ovens - might blow.)
If the main power fuse is located in the primary of the high voltage transformer rather then at the line input, the clock and touchpad will work but the fuse will blow upon initiating a cook cycle. Or, if the fuse has already blown there will simply be no heating action once the cook cycle is started. There are other variations depending on whether the cooling fan, oven light, and so forth are located down stream of the fuse.

Some models may have a separate high voltage fuse. If this is blown, there will be no heating but no other symptoms. However, high voltage fuses are somewhat rare on domestic ovens.

A number of failures can result in the fuse NOT blowing but still no heat:


  • Bad connections - these may be almost anywhere in the microwave generator or the primary circuit of the HV transformer. A common location is at the crimp connections to the magnetron filament as they are high current and can overheat and result in no or intermittent contact. See the section: See the section: Testing the magnetron.
  • Open thermal protector - usually located on magnetron case. Test for continuity. It should read as a dead short - near zero ohms. See the section: Testing thermal protectors and thermal fuses.
  • Open thermal fuse - some ovens have one of these in the primary circuit. It may be in either connection to the HV transformer or elsewhere. Test for continuity. It should read as a dead short - near zero ohms.
  • Open HV capacitor - see the section: Testing the high voltage capacitor. A shorted HV capacitor would likely immediately blow the fuse.
  • Open HV diode - see the section: Testing the high voltage diode.
  • Open magnetron filament - This failure may also be due to loose, burnt, or deteriorated press (Fast-on) lugs for the filament connections and not an actual magnetron problem. See the section: Testing the magnetron.
  • Open winding in HV transformer. See the section: Testing the high voltage transformer.
  • Defective HV relay. A few models use a relay in the actual high voltage circuitry (rather than the primary) to regulate cooking power. This may have dirty or burnt contacts, a defective coil, or bad connections
  • Shorted HV diode - see the section: Testing the high voltage diode.
  • Short or other fault in the magnetron - see the section: Testing the magnetron.
  • Short in certain portions of the HV wiring. See the section: Testing and repairing the wiring and connections.

Depending on design, a number of other component failures could result in no heat as well including a defective relay or triac, interlock switch(s), and controller.


If you are interested in doing it yourself the following link will help : Microwave Repair Manual

(**All the above references to tests are found here)

Oct 21, 2010 | Kenmore 63663 Microwave Oven

1 Answer

HV Transformer and Maganatron


I would not recommend an inexperienced measuring secondary voltage on the high voltage transformer! The filament winding produces about 3VAC but the high voltage winding produces well over 2000VAC! And that can be instantly lethal!

I would only recommend measuring the resistance (in ohms) of the windings with power off and capacitor discharged.

We have the full service manual for this model and have uploaded it to our site here to help you.

You will need the free Acrobat Reader to view or print it.

The part number listed by the distributor for the high voltage transformer is RTRN-A527WRE0 (zero on the end, not "oh") which is the same number shown in the service manual.

The two continuity checks on a magnetron are across the filament terminals, which should read about zero ohms, and from each terminal to the case, which should read open or infinity.

Even if a magnetron passes these continuity tests, it can still be bad.

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

Oct 04, 2008 | Sharp R-930AK Convection/Microwave Oven

1 Answer

Oven won't heat even though each component seems to be functional.


Even though the magnetron passed the continuity tests, it can still be bad. In fact, most of them fail in ways that do not show up in continuity tests.

And I am 99% certain yours is bad, especially since you have proven that the filament voltage and high voltage DC is being produced and sent to the magnetron.

I must say that the testing you have done is not recommended for people without plenty of experience, but apparently you did it safely. Please don't press your luck, since the high voltage can be instantly lethal.

For Goldstar / LG / L.G. parts, call 1-800-243-0000 (M-F, 7am-8pm CT, Sat 8-5 CT) and choose the appropriate prompt from the menu or visit here.

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

Jul 17, 2008 | LG LRM1250 Microwave Oven

2 Answers

No Heat


ALL functions work.... just no heat? Is that right? I am assuming that the control (computer?, relays?) ARE supplying power to the magnetron.

IF everything checks out as you say, is the magnetron filament O.K.? (You have to disconnect it from the transformer to test it.)

If the magnetron transformer draws 8 amps, it sounds like it's O.K. cause if it was shorted, it would blow a fuse, and if it was open, it wouldn't draw ANY current.

Check it out, tell me more and let me know. No heat means the Magnetron isn't working.

Mar 30, 2008 | LG LRM1250 Microwave Oven

1 Answer

Model 62252/62253/62259


If you removed wires to test mag tube and it's not infinite from either terminal to ground, it's shorted. Mag tubes will buzz like that. Also check high-voltage diode. Should have infinite in 1 direction. If in doubt, replace also.

Nov 22, 2007 | Kenmore 62622 Microwave Oven

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