Microwave Oven Makes Noise Like A Geiger Counter

Nigel Goodwin said:

You need to bear in mind that CRT TV was high voltage/low current, so not particularly dangerous - microwave ovens though WILL kill you - no if's or but's, it's highly likely to be fatal.



High voltage arcing isn't really something microwave ovens do, and the fact it's an inverter oven means it would almost certainly just kill the inverter (I used to have a pile of duff inverters at work, 'just in case' they might come in handy - they never did ). Fan problems are pretty rare, but as you've already seen, turntable motors are a common failing.

I presume it's not just arcing on the waveguide cover?, which can be quite common, and due to not keeping it clean - we used to sell a LOT of waveguide covers (one of the few parts you're allowed to sell).

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Thanks for the reply.

I have had several microwave ovens in the past and each one had a problem with the waveguide cover. Sometimes they burnt a little after a long time use of the oven. I believe it was because they had a small amount of grease on them for too long as you were saying. This taught me a lesson. After maybe the third or fourth oven i started placing a covering of clear plastic food wrap over the waveguide cover so that when any grease got on it i could just peel it off and replace it with a new layer. It just takes a minute to change and the plastic warp adheres to the cover no problem just like it sticks to food. On this oven i did it as soon as i got it so over the four or five years i have had this oven now i changed it several times, and it works so well that the waveguide cover still looks like it is brand new.
Also, the plastic wrap that is on there now is perfectly clean so i dont think it would be arcing there and i think that would make a different noise too and i would probably see flashes of light. I dont see any flashes of light inside the oven and i dont see any looking in the thin cracks between the cover and the front panel.
I would take the cover off but it would take a bit of moving stuff around to get to it in such a way that i could do that. That will have to wait for a while unfortunately.

Funny also is that yesterday it did not make any of that noise at all but other days before that it did. The noise also does not appear to be constant even over one cooking period. Like heating a cup of water, when it does make the noise the noise will start, then stop, then start again, then stop again, etc., all while the 3.5 minute cooking period is progressing.
Really strange but then again i guess that's the way problems are.
I also use it almost exclusively on power level 3 which is a lot lower than power 10 so i thought it would be 'easier' on the tube and other parts but that's just a guess.

MrAl said:

Thanks for the reply.

I have had several microwave ovens in the past and each one had a problem with the waveguide cover. Sometimes they burnt a little after a long time use of the oven. I believe it was because they had a small amount of grease on them for too long as you were saying.

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Yes, caused by poor cleaning.

I also use it almost exclusively on power level 3 which is a lot lower than power 10 so i thought it would be 'easier' on the tube and other parts but that's just a guess.

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As it's designed to run on full power, I would imagine that is best - running it at lower power (in an inverter oven) means it's running at a lower heater voltage, and may struggle to fire up.

Nigel Goodwin said:

Yes, caused by poor cleaning.



As it's designed to run on full power, I would imagine that is best - running it at lower power (in an inverter oven) means it's running at a lower heater voltage, and may struggle to fire up.

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Hi Nigel,

I forgot to mention that maybe a year ago the bulb burned out and because this bulb and socket combination (all in one not removable) was unique to that oven to get a new one would cost 20 dollars USD. When i priced a replacement LED bulb and socket the bulb made for ovens, i decided to go LED. I installed it very carefully of course, and the bulb does not flicker at all.
So i dont think the bulb has anything to do with it, especially since it worked for around a year already, but you may feel differently about that with your vast experience in repairs on these things.

MrAl said:

Hi Nigel,

I forgot to mention that maybe a year ago the bulb burned out and because this bulb and socket combination (all in one not removable) was unique to that oven to get a new one would cost 20 dollars USD. When i priced a replacement LED bulb and socket the bulb made for ovens, i decided to go LED. I installed it very carefully of course, and the bulb does not flicker at all.
So i dont think the bulb has anything to do with it, especially since it worked for around a year already, but you may feel differently about that with your vast experience in repairs on these things.

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A lot of the manufacturers seemed to change from cheap easily replaceable screw in bulbs, to ones with moulded in push on tags - always seemed a VERY backwards step to me, and as you say allowed them to charge even more outrageous prices for the lamps.

However, you shouldn't be able to buy the lamps anyway, as they aren't consumer replaceable - most of the screw-in ones weren't either, but I suspect that was another reason why they moved to the stupid new ones.

Nigel Goodwin said:

A lot of the manufacturers seemed to change from cheap easily replaceable screw in bulbs, to ones with moulded in push on tags - always seemed a VERY backwards step to me, and as you say allowed them to charge even more outrageous prices for the lamps.

However, you shouldn't be able to buy the lamps anyway, as they aren't consumer replaceable - most of the screw-in ones weren't either, but I suspect that was another reason why they moved to the stupid new ones.

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Oh yeah some good points. I never could see how they could design something where you had to take off the entire cover to replace a single little tiny light bulb. And to make it worse, they use at least one very strange head screw that requires a special tool to get out so the cover comes off.

I suspect that many consumers just run it dark when the bulb goes out. I cant see anyone bringing or shipping this to a service center just for bulb replacement.
I suspect that others run it dark for a while then go out and get a new oven.

As for me, i was going to run it dark but a neighbor suggested i switch to LED and when i priced everything i realized LED was the same price so i went with that. The only unusual part of the replacement was i had to crimp two lugs on the ends of the wires with the new socket so they would mate with the lugs that were there already for the old socket. After that it was a breeze as the new socket fit with the screw and tab of the old socket so no physical alteration was needed just plain electrical.

Just used it again a few minutes before writing this for my morning coffee. No noise this morning. I'll see how it acts later today when i make lunch or din din.

Oh yeah, as to the LED replacement for the regular bulb, it's a little bit better but nothing to scream about. I would tell anyone else that wanted to do this not to do it unless their bulb burnt out because it's not worth the effort unless you really need to do it. The amount of light isnt much more, although the color is white instead of that orange yellow we get from incandescent bulbs.
As to the life of the LED bulb, i can t say for sure how long it lasts i have to go by what the manu says when i bought it. There is one good point though, if it does blow out i have a regular socket now so i can pup anther LED or incandescent bulb in there (once the cover is off that is). I have a spare LED too cause i had to buy two of them at once but they screw in so that's a little nicer than before with the Panasonic priority socket/bulb combo.

I looked up the date that i bought this microwave oven.
At the beginning of January 2021 i had it for 8 years. I payed $129.00 dollars (USD) for it.
I believe a similar oven today would cost $179.00 dollars (USD) but possibly it would be a bit bigger.
There are cheaper ones though from other manufacturers with similar 'features' and size 1.2 cu ft.

The thing i really dont like about it though is that i have to press the "POWER button 8 times to get to power level 3, and i use that power level all the time.

Well I just looked on Panasonic UK, and it's a bit vague if they are inverter or not - but a 23 Litre capacity inverter one is £115.

Nigel Goodwin said:

Well I just looked on Panasonic UK, and it's a bit vague if they are inverter or not - but a 23 Litre capacity inverter one is £115.

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Wow that sounds high. I guess that is equivalent to about a 0.8 cu ft microwave, and that price is around 160 dollars USD if i am right. That would be considered very high for a 0.8 cu ft oven here. Combo convection ovens may run a little higher though.

Did not hear the noise this morning either. I would get a new one but i cant find an inverter type with the features i want.

MrAl said:

Wow that sounds high. I guess that is equivalent to about a 0.8 cu ft microwave, and that price is around 160 dollars USD if i am right. That would be considered very high for a 0.8 cu ft oven here. Combo convection ovens may run a little higher though.

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That wasn't a combi, those are like £300 for a Panasonic inverter model.

gary350 said:

A dirty greasy oven can have 100s of tiny sparks all over the dirty walls & ceiling that can make crazy clicking sounds.

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occasionally i have seen gunk residue build up on the magnetron's antenna insulator and arc over.... most microwaves have a plastic or some kind of insulating "window" between the waveguide box and the oven cavity... those "windows" occasionally get loose and vapors from food get into the waveguide box, and can build up on the magnetron's antenna. dust gunk buildup can cause arcing across the insulator surface.

unclejed613 said:

most microwaves have a plastic or some kind of insulating "window" between the waveguide box and the oven cavity...

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It's called a 'waveguide cover' and has been mentioned extensively in the previous posts

It's usually made out of mica.

unclejed613 said:

occasionally i have seen gunk residue build up on the magnetron's antenna insulator and arc over.... most microwaves have a plastic or some kind of insulating "window" between the waveguide box and the oven cavity... those "windows" occasionally get loose and vapors from food get into the waveguide box, and can build up on the magnetron's antenna. dust gunk buildup can cause arcing across the insulator surface.

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Oh that is interesting. I dont think mine is loose but i'll check anyway.
I use plastic wrap over the "waveguide cover" mica piece (see Nigel's post) and it overlaps the edges significantly. It sticks right to the metal side of the oven when i place it there and smooth it out with my hand. It's easy to do and keeps junk off the cover. I peel it off and replace it now and then. So it is a waveguide cover cover , a cover for the waveguide cover I highly recommend this to anyone who uses a microwave.