Question about Microwave Ovens

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Microwave - no heat

All functions work fine, but no heat. The fuse and all thermal cutouts are good. I replaced the HV diode (was shorted), and the HV cap checks good. I've read that the magnetron filament should measure "less than 1 ohm." Mine measures 0.04 ohms, seems a bit low, but I don't know. Also, all 3 windings of the HV transformer look OK.

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  • ronfeole Jul 14, 2008

    The unit is a GE Spacemaker model JVM1642. I rechecked the HV transformer windings with Gallawa's specs and verified all interlock contacts. Seems like it has to be the magnetron. Any way to verify it, since the filament looks good and is not shorted to ground?

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  • Microwave Ovens Master
  • 8,820 Answers

The filament reading sounds fine.

Here are some links you or someone you know can use for test help, but read their safety warnings first:

http://www.gallawa.com/microtech/mag_test.html
http://www.gallawa.com/microtech/xformer.html

Many brands have a "mini-manual" hidden inside the unit behind the control panel or hidden on the left side behind the grille, which is very helpful when troubleshooting & testing.

Please reply back with your brand and model number if you need further help.

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

Posted on Jul 12, 2008

  • William Miller
    William Miller Jul 19, 2008

    It's virtually certain it's the magnetron.

    Please also see tiway's comment for more detail.

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

  • William Miller
    William Miller Jul 20, 2008


    IMPORTANT

    If
    it's within the magnetron portion of the warranty (usually 5-9 years)
    but out of the original full warranty (usually 1 year) GE should send you a new magnetron.

    They way I do it is to contact GE Customer Service. I suggest calling them with your brand, model, serial, and date of manufacture. The they should transfer you to the parts section of the warranty department, who will send out a new magnetron.

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




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Please provide the brand and model number of the unit.

If you had a shorted diode, there's a chance the magnetron is bad as well. (Especially if you happen to have a GE model)


Posted on Jul 12, 2008

  • Tim martin
    Tim martin Jul 14, 2008

    If you can remove the magnetron tube, look at the top (antenna). The silver cap should be nice and shiny. If it looks like its been hot or burnished or flat out burned it's probably bad.
    If your mag tube reads "OM75 P (10)" on the label and it's manufactured by Samsung, it's probably bad. The original versions of these tubes have an enormous failure rate.
    Here's a link where you can view this tube ...
    http://shop.vendio.com/tway/item/9342544...


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1 Answer

My one year old microwave just stopped working. The light is on, but nothing else.


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

here are some issues, but you still maybe under warranty.
  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's. take the time to rate us.Thanks and good luck

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Jan 05, 2011 | Goldstar MV-1501 Microwave Oven

Tip

Troubleshooting Guide


  • Problem: Totally dead oven.
    Possible causes:
    1. No power to outlet (blown fuse or tripped breaker or GFCI).
    2. Blown main fuse - likely due to other problems.
    3. Open thermal protector or thermal fuse.
    4. Defective controller or its power supply.
    5. Clock needs to be set before other functions will operate (some models).

  • Problem: Totally dead oven after repair.
    Possible causes:
    1. Cabinet screws replaced in incorrect location (safety interlock not engaged).
    2. Any number of screwups. :)

  • Problem: No response to any buttons on touchpad.
    Possible causes:
    1. Door is not closed (some models).
    2. You waited to long (open and close door to wake it up).
    3. Controller is confused (pull plug for a minute or two to reset).
    4. Defective interlock switches.
    5. Faulty controller or its power supply.
    6. Touchpad or controller board contaminated by overenthusiastic cleaning.
    7. Defective/damaged touchpad.

  • Problem: Oven runs when door is still open.
    Possible causes:
    1. Damaged interlock assembly.
    2. Cooling fans (only) running due to bad sensor or still warm.

  • Problem: Oven starts on its own as soon as door is closed.
    Possible causes:
    1. Defective triac or relay.
    2. Controller is confused (pull plug for a minute or two to reset).
    3. Defective controller or its power supply.
    4. Touchpad or controller board contaminated by overenthusiastic cleaning.
    5. Defective/damaged touchpad.

  • Problem: Oven works but display is blank.
    Possible causes:
    1. Defective controller or its power supply.
    2. Broken display panel.
    3. Oven needs to be reset (pull plug for a minute or two to reset).

  • Problem: Whacked out controller or incorrect operation.
    Possible causes:
    1. Previous or multipart cook cycle not complete.
    2. Controller is confused (pull plug for a minute or two to reset).
    3. Defective controller or its power supply.
    4. Touchpad or controller board contaminated by overenthusiastic cleaning.
    5. Defective/damaged touchpad.
    6. Defective sensor (particulalry covection/mirowave combos).

  • Problem: Erratic behavior.
    Possible causes:
    1. Previous or multipart cook cycle not complete.
    2. Bad connections in controller or microwave generator.
    3. Faulty relay - primary (or HV side, much less commonly used).
    4. Defective controller or its power supply.
    5. Bad contacts/connections on mechanical timers. Intermittent fuse.
    6. Power surge at start of cook cycle confusing controller.
    7. Microwave (RF) leakage into electronics bay.

  • Problem: Some keys on the touchpad do not function or perform the wrong action.
    Possible causes:
    1. Touchpad or controller board contaminated by overenthusiastic cleaning.
    2. Defective/damaged touchpad.
    3. Controller is confused (pull plug for a minute or two to reset).
    4. Faulty controller.

  • Problem: Microwave oven does not respond to START button.
    Possible causes:
    1. Defective START button.
    2. Faulty interlock switches.
    3. Door is not securely closed.
    4. Faulty controller.
    5. You waited too long - open and close door to wake it up!

  • Problem: 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. Defective HV relay (not commonly used).

  • Problem: Timer and light work but no heat, cooling fan, or turntable rotation.
    Possible causes:
    1. Defective (lower) door interlock switch or door not closing fully.
    2. Faulty relay or triac.

  • Problem: Fuse blows when closing or opening door:
    Possible causes:
    1. Defective door interlock switch(s).
    2. Interlock switch knocked out of position.
    3. Misaligned door.

  • Problem: Loud hum and/or burning smell when attempting to cook.
    Possible causes:
    1. Shorted HV diode, magnetron.
    2. Burnt carbonized food in or above oven chamber.
    3. Shorted winding in HV transformer.
    4. Frayed insulation on HV wiring.

  • Problem: Arcing in or above oven chamber.
    Possible causes:
    1. Burnt carbonized food deposits.
    2. Exposed sharp metal edges.

  • Problem: Fuse blows when initiating cook cycle.
    Possible causes:
    1. Defective interlock switches or misaligned door.
    2. Shorted HV capacitor.
    3. Shorted HV diode.
    4. Shorted magnetron (probably won't blow main fuse but HV fuse if used).
    5. Defective triac.
    6. Old age or power surges.
    7. Defective HV transformer.
    8. Short in wiring due to vibration or poor manufacturing.

  • Problem: Fuse blows when microwave shuts off (during or at end of cook cycle).
    Possible causes:
    1. Defective triac (doesn't turn off properly).
    2. Defective relay.
    3. Shorting wires.

  • Problem: Oven heats on high setting regardless of power setting.
    Possible causes:
    1. Faulty primary relay or triac or HV relay (not commonly used).
    2. Faulty controller.

  • Problem: Oven immediately starts to cook when door is closed.
    Possible causes:
    1. Shorted relay or triac.
    2. Faulty controller.

  • Problem: Oven heats but power seems low or erratic.
    Possible causes:
    1. Low line voltage.
    2. Magnetron with low emission.
    3. Faulty controller or set for wrong mode.
    4. Stirrer (or turntable) not working.
    5. Intermittent connections to magnetron filament or elsewhere.
    6. Faulty primary relay or triac or HV relay (not commonly used).

  • Problem: Oven heats but shuts off randomly.
    Possible causes:
    1. Overheating due to blocked air vents or inoperative cooling fan.
    2. Overheating due to bad magnetron.
    3. Bad connections in controller or microwave generator.
    4. Faulty interlock switch or marginal door alignment.
    5. Faulty controller.
    6. Overheating due to extremely high line voltage.
    7. Stuck stirrer fan resulting hot spots detected by sensors.

  • Problem: Oven makes (possibly erratic) buzzing noise when heating.
    Possible causes:
    1. Fan blades hitting support or shroud.
    2. Vibrating sheet metal.
    3. Vibrating transformer laminations.
    4. Turntable or stirrer hitting some debris.

  • Problem: Oven light does not work.
    Possible causes:
    1. Burnt out bulb :-).
    2. Bad connections.

  • Problem: Fans or turntables that do not work.
    Possible causes:
    1. Gummed up lubrication or bad motor bearing(s).
    2. Loose or broken belt.
    3. Bad motor.
    4. Bad thermostat.
    5. Bad connections.

on Mar 30, 2008 | Kenmore 80412 Microwave Oven

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.

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

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Jan 05, 2011 | Kenmore 63792 Microwave Oven

1 Answer

It's not heating food, sounds louder than normal and smells like something possibly electrical is burning (or just getting too hot), but it looks as if it's working (lights up, tray moves inside, timer...


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

Here are some issues 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 use
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's. take the time to rate us.Thanks and good luck

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Jan 04, 2011 | Maytag MMV5207BAW 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.

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

4 Thumbs - Very Helpful
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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.

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

4 Thumbs - Very Helpful
3 Thumbs - Helpful

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

Hi, I have a SHARP Microwave Model R398F. Its less than a year old. The display and timer work fine but does not heat up. Can you please let me know what the problem could be. Thanks Js


If the operation is otherwise normal with the exception of heating food, common causes include; (to diagnose requires discharging of the HV capacitor) if you are inexperienced with working with HV I suggest seeking professional help.

Open thermal protectors or thermal fuses.

Open HV Diode.

Open HV capacitor

Open magnetron filament

Open winding in HV transformer

Defective HV relay

Shorted HV diode

Short or other fault in the magnetron

Short in certain portions of the HV wiring

Replacement Magnetrons (the most likely cause if not charring or defective components are found when troublshooting the small parts, can typically be had for around $45.00 just do a web search for your model number.

Good Luck

Sep 07, 2010 | Sharp Microwave Ovens

4 Answers

GE Microwave problems after HV capacitor replacement???


The rectifier diode could indeed be bad. But first I would want to know what value (in uF) the old one was and what is the value of the new one? If they're too far off, the difference in the capacitive reactance could throw off the "tuning" of the circuit. The uF value of the capacitor is optimized in relation to the other components used in the system. Of course, you'd also want to be sure your new cap is at or slightly above the working voltage rating of the old one, too.

Jan 04, 2007 | GE JVM2050 Microwave Oven

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