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I understand the current draw issues of a Microwave. My 1 Yr. Old Microwave had been running fine for the past year. It is Plugged into a 20AMP circuit and the only thing on that circuit. The Microwave and the Lights in the House had been fine no flickering and no dimming. Recently as of Yesterday when the Microwave runs the LED Lights in the house will flicker / blink from time to time and some of them actually dim - depending on the brand of LED Light.

I do not notice my incandescent lamps doing anything unusual. None of my other devices such as TV seem to be effected.

Why is this now happening ? Is there any a real fact based cause that someone can provide for me and perhaps things to check or solutions.

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    The power line in filter on microwave is broken/defective. It supposed to filter out the frequency going back in the power line causing disturbance. The incandescent do not care about that, but LED lamps do care.
    – Traveler
    Feb 1, 2023 at 0:49
  • @Ruskes that sounds plausible - I did not think that the unit had the filter on the line being an appliance but thinking on it makes sense. I will look into the parts diagram online.
    – Ken
    Feb 1, 2023 at 0:54
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    Are the LED lights new? What else has changed? You may have a lost neutral. Plug the microwave somewhere else in the house to see if the problem persists. Do the lights flicker when other appliances are running, like electrical stove, dryer, washing machine?
    – P2000
    Feb 1, 2023 at 1:31
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    Use a multimeter to check voltage on each line to neutral, each line to ground and neutral to ground. Easiest is if you have a 240V/120V typical US clothes dryer on a 4-prong receptacle. If not, check several receptacles to (hopefully) get some on one hot line and some on the other. The concern is if you have a loose or broken connection on one wire at the street, at the meter or entering the main panel then you will get some strange results, and that can cause a lot of problems. If you have ~ 120V (anywhere 110V to 125V is OK as long as it is consistent and within a volt for the two hot Feb 1, 2023 at 3:32
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    GFCI tests hot vs. neutral from that point forward. If you lost neutral coming into the house then the voltage for hot to neutral on a branch circuit would be wrong but the current would still be balanced and the GFCI would likely not trip. Feb 1, 2023 at 4:16

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As you can imagine the microwave generates high frequency interference operating at 2.5 GHz.

Mostly it sufficiently isolated to protect you from those frequencies but it is cooking anything in the microwave oven.

To prevent those EMI going out on the power cord there is a EMI filter in line.

Yours seems to be broken. When the EMI reaches the LED it will make it malfunction. LED lights depend on clean sinusoidal wave, which you do not have.

The incandescent lights do not care about EMI, they are just hot/glowing wire.

To test use a power-bar with line filter.

The EMI filter is a small box (metal) where the power cable is connected to.

You will have to open the microwave to see it, and get the model/part number from it to buy replacement.

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    To confirm this, the OP can buy a plug-in line filter or power-bar with line filter, and try it out first.
    – P2000
    Feb 1, 2023 at 3:46
  • @P2000 that would be the fix
    – Traveler
    Feb 1, 2023 at 3:47
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    yes, but I meant before buying a special part and opening the microwave. It's sometimes easier to return an item to an on-line giant or home improvement giant than deal with special orders.
    – P2000
    Feb 1, 2023 at 3:49
  • @P2000 also that is good sugestion
    – Traveler
    Feb 1, 2023 at 3:51

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