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Thread: LG Microwave runs but wont heat anything

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    Senior Member skozzy's Avatar
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    Default LG Microwave runs but wont heat anything

    Anyone got some ideas what can be wrong with my Microwave. Last night it stopped heating food, yet it sounds like its running, I hare a relay or something switch when I press start. What I don't hear which i usually do is a thud or thump that sounds like a magnet engaging.



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    I suggest that it's nothing the amateur can fix or even attempt to.

    The magnetron inside the oven, which generates microwave energy used to heat food, operates at an extremely high voltage and much care should be exercised if you don't wish to become a statistic.

    Also, microwave energy is dangerous to humans, which is the reason that the oven's cabinet is made from metal. This ensures that microwave energy does not escape.

    Elaborate shielding around the door helps to keep microwave energy to a safe level for operator safety.

    Microwave ovens should be serviced only by qualified technicians, who know the risks and therefore take adequate precautions to ensure their own safety.

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    LSemmens
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    While Skozzy is quite correct, if you are comfortable with electronics, the Magnetron is no different to any other component, and can be replaced at home, I have done so many years back, but, the cost of a microwave oven makes it uneconomical these days. Just toss it and buy a new one.
    I'm out of my mind, but feel free to leave a message...

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    gulliver (28-08-17)

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    Senior Member BCNZ's Avatar
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    Let me start by saying that if you aren't experienced in working with high voltage, don't even take the cover off to have a look.
    Microwave ovens have around 2-3 kV (yup, that's 2000 - 3000 volts) inside, and at currents of several amps.
    Not only is this enough to kill you very quickly, it will hurt the whole time you're dying.
    In fact, there is more danger in a microwave oven than what there was in a large CRT TV.

    With that out of the way, it may be the magnetron, but it can be a few other things such as a faulty relay, shorted HV capacitor, shorted 'shorts' protection diode, or shorted HV diode.
    In some older ovens there's a high voltage fuse which feeds the magnetron. If the filament shorts to the case (not uncommon) this fuse will blow and you'll get no heat.
    If the fuse is blown then the magnetron is toast - a check with a meter will confirm the short.
    In the case of modern inverter ovens, there's an electronic control board which is the HV power supply and drives the magnetron.
    Quite common for these to fail, in which case you need to determine if the board died on its own or if a shorted magnetron helped it.

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    I just had a recent microwave problem and searched for a long time for my solution couldn't find one so i looked through a few repair clips in general the main reason they say is the micro switches on the door that are faulty but make sure not to touch or make sure the large capacitor is discharged before trying anything especialy if it was recently plugged in
    Find a clip online that shows you where everything in the microwave is and safety precausions even if you are familiar with electronics you may have missed something important - better to be safe then sorry

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