Microwave Oven Makes Noise Like A Geiger Counter

[MrAl]

A couple weeks ago my microwave oven started making noises like a Geiger Counter detecting a small amount of radiation (slow but constant low frequency click that is sort of garbled.

I read this on the web so far:
" If your microwave is making noises like a Geiger counter, the sound is coming from the magnetron that produces the microwaves. The sound is normal and there's no reason to be alarmed. If your microwave makes noises when it's in standby that are somewhat loud or strange, something could be wrong with your fan run on. "

But this sound never came out of it before about two weeks ago and i had it for at least 2 years now.

Any ideas?

Thanks.

 

[Nigel Goodwin]

A couple weeks ago my microwave oven started making noises like a Geiger Counter detecting a small amount of radiation (slow but constant low frequency click that is sort of garbled.

I read this on the web so far:
" If your microwave is making noises like a Geiger counter, the sound is coming from the magnetron that produces the microwaves. The sound is normal and there's no reason to be alarmed. If your microwave makes noises when it's in standby that are somewhat loud or strange, something could be wrong with your fan run on. "

But this sound never came out of it before about two weeks ago and i had it for at least 2 years now.

Any ideas?

Thanks.

I've repaired thousands of microwave ovens - and never heard any such thing, so certainly not 'normal'.

What happens if you use it on defrost?, does the noise change (defrost is normally 7 seconds OFF and 3 seconds ON).

 

[MrAl]

Hi Nigel thanks for the reply.

Well this is an inverter type Panasonic.
Unfortunately i cant use it on Defrost because it draws too much power from the mains line. For that reason i never use it for defrosting i set it to 1 or 2 to defrost and that uses only about 600 watts from the mains line.
The voltage during cooking at power 3 is pretty normal though, at least 110vac typically 115vac i monitor it all the time. That is what i cook at when i hear the noise and that is mostly what i use anyway.
It does not pulse on and off because it is an inverter type and for this oven power levels 3 to 10 do not pulse.

What i could do is try to get a audio recording of the noise. I dont know if this site allows uploading of audio files of any type but i could check i guess.

Strangest noise i ever heard and it goes away sometimes then comes back without changing anything.

 

[Nigel Goodwin]

Hi Nigel thanks for the reply.

Well this is an inverter type Panasonic.

Well an inverter type is completely different to a normal microwave

Unfortunately i cant use it on Defrost because it draws too much power from the mains line.

I don't see why it would take any more? - but not much point anyway, as it's not a conventional microwave, and not pulses ON and OFF.

Everyone of those I've seen (both under warranty and out of warranty) has had a failed magnetron, and a blown inverter - they don't seem very good, and all just to make it a bit lighter to carry

 

[MrAl]

Well an inverter type is completely different to a normal microwave



I don't see why it would take any more? - but not much point anyway, as it's not a conventional microwave, and not pulses ON and OFF.

Everyone of those I've seen (both under warranty and out of warranty) has had a failed magnetron, and a blown inverter - they don't seem very good, and all just to make it a bit lighter to carry

Hi again and thanks for the reply,

Just thought i would point out the difference between defrost and non defrost.
First, when i set the power level to a power level setting that is less than 10, the oven power draw from the mains line is always less than the full power when it is set to 10. On power level 10 it draws about 16 amps from the mains line. On power level 3 it only draws about 5 amps. Those current levels are both continuous because this kind of oven as you know does not pulse on and off like the older style ovens. So the cooking power is continuous on levels 3 to 10 and so is the input power and input current.

Switching to level 3 draws 5 amps, but switching to Defrost first draws the full power and so the current is 16 amps to start with. As the defrost time progresses this will eventually come down to lower and lower levels and i dont know the exact behavior here because i cant really use it i can only turn it on for a couple seconds and then i have to stop it because it draws the line down too low. From what i have seen of other ovens they stay at full power and then a little while later they start to pulse on and off, and the pulses get farther and farther apart so they can lower the average power and average cooking level to the food so it only defrosts but does not really cook.
So anyway the main point is that when set to defrost on this oven it starts out at the maximum power setting so i cant really use it.

Normally i use this over at a very very reduced power level not only so that it draws less power from the line (600 watts vs about 1600 watts or higher) but it also cooks the food more gently and so comes out more tender.
The inverter technology was a good idea and i have experimented with using a variac on a regular oven to lower the power and it is almost the same but harder to control like that. The inverter types are now appearing on many other brands too like Oster, where i think Panasonic was the first one to come out with this so maybe they are licensing the technology to other manufacturers now i dont know for sure yet though.

The biggest downside to Panasonic ovens is the power level setting can only be set by pushing ONE button many times. To get to power level 3 i have to push the power button eight (8) times! Now this might not seem that bad but i use the oven a lot so i have to constantly go through that day after day after day. The old way of doing it was to press power then press the power button level you wanted like "3". So it would be like: "Power", then "3", and that's it you are done setting the power. But with this kind of power setting it's just nuts. I know other ovens are like that too and they all bite.
It also has no memory function so you can set power level 3 and assign it to a two button sequence. I do see this appearing on other ovens though from other manus lately.

Another downside is that there is no "BEEP" disable function on this and many other ovens. So you cant disable the beep unless you take apart the oven and break one of the connections or jam something into the buzzer diaphragm.

I guess i got off the original issue but sometimes i wonder who the heck is designing these things, could it be a blind and deaf circuit designer? (ha ha)

Anyway, if you know of a oven model with inverter technology and has a regular power setting like POWER then 3 that would be great. If it has memory function too that would be great too. Size up to maybe 1.4 cubic feet.
Any suggestions would be cool. Maybe i will use this problem as an opportunity to get a new one with function buttons that are not ridiculous.

Thanks.

 

[Nigel Goodwin]

The inverter technology was a good idea and i have experimented with using a variac on a regular oven to lower the power and it is almost the same but harder to control like that. The inverter types are now appearing on many other brands too like Oster, where i think Panasonic was the first one to come out with this so maybe they are licensing the technology to other manufacturers now i dont know for sure yet though.

I wasn't aware of any others, it's basically failed technology - too expensive, too complicated, too unreliable, and for no real advantage. I suspect Panasonic probably lost a lot of money from it?.

The problem with a variac, or indeed the inverter technology, is the magnetron heater - by lowering the voltage you're reducing the heater voltage, making the magnetron less likely to fire up.

 

[gary350]

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

 

[MrAl]

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

Thanks for the idea.

I can agree with that but this oven is not dirty and i cleaned it again about a week ago.
Any other ideas appreciated.

 

[MrAl]

I wasn't aware of any others, it's basically failed technology - too expensive, too complicated, too unreliable, and for no real advantage. I suspect Panasonic probably lost a lot of money from it?.

The problem with a variac, or indeed the inverter technology, is the magnetron heater - by lowering the voltage you're reducing the heater voltage, making the magnetron less likely to fire up.

Well i dont know about failed technology but this does fit my needs because of the way it draws power which is in a continuous mode rather than pulsed like previous ovens did. That's very important here because i can turn it down to a lower power so it draws less current. The other ovens would draw around 10 amps ro more, then maybe around 0.5 amps, then 10 amps again, then 0.5 amps again, etc., etc., and that means that sometimes it draws a lot of current. It's also annoying to hear the pulsing on and off and i wonder what would happen if a lot of people on the block had their ovens all pulsing on and off at the same time.

Back when i worked in the power control industry, we worked with Sandia Labs on a solar project that involved lined tied inverters. They didnt want inverters coming on line and off line all the time which causes various harmonic problems on the line so they wanted to be able to disable the automatic system if they wanted to. So i wonder if the pulsing would be a similar problem.
The grid in the USA is very sensitive and right now somewhat vulnerable. It is a complex problem that is just being looked at now. They keep adding homes and apartment buildings and air conditioners and the grid keeps getting loaded down.
They are considering an infrastructure upgrade with the new President, but then they all said that but never did anything about it yet.

When i went out to Los Angeles recently i noticed in the power in the friends home i went to visit did not seem to have too much of a problem. It's funny that in a place that has problems with the electric it would be better than here.

 

[augustinetez]

I don't know if that model has as stirrer fan, but other models have been known to make odd sounds when it gets stuck.

Also the Magnetron cavity cover can track across and cause the same symptoms you are describing.

As mentioned above, the Magnetron could also be faulty.

 

[gary350]

Factory workers are notorious for playing pranks on each other it makes the work day more fun. People where I worked use to throw a paper clip into some ones paper lunch bags when they put there whole lunch bag into the lunch room microwave it made popping sounds then catch on fire in about 3 seconds. LOL.

Some paper food packages are laminated with aluminum foil hidden between 2 layers of paper the package makes popping & cracking sounds in the microwave. If your heating something in the original factory package try heating it in a different package. Look see if package says it is microwaveable.

Sometimes factory workers stuff their used lunch bag trash inside the produces the factory makes and sells home owner never knows what is hidden inside places they can not see. There could be something hidden in your microwave wave guide like a paper clip or piece of wire.

There is a plastic or glass wave guide cover in your microwave remove it look see what you can find inside the wave guide. It is also possible the high voltage transformer has a defect it could be sparking. Put 1 end of a 2 foot long rubber hose in 1 ear move the other end of hose around the microwave to listen for the sound you hear. Hose makes it easy to locate strange sounds. You might need to remove the oven case to listen inside.

Look inside the microwave fan for paper or plastic wrappers.

 

[JimB]

Sometimes factory workers stuff their used lunch bag trash inside the produces the factory makes and sells home owner never knows what is hidden inside places they can not see. There could be something hidden in your microwave wave guide like a paper clip or piece of wire.

And as time goes by, they are up in arms because the factory has closed, they are on the dole, and production has moved to China (other low labour cost locations are available).

Someone said: "Make America great again".

JimB

 

[MrAl]

And as time goes by, they are up in arms because the factory has closed, they are on the dole, and production has moved to China (other low labour cost locations are available).

Someone said: "Make America great again".

JimB

Good point. Imagine if we did our own manufacturing of all this stuff again, things would be booming just like a long time ago. Damn the manu's who moved overseas. Yeah it results in cheaper stuff, but then again cheaper is actually really cheaper.

 

[MrAl]

I don't know if that model has as stirrer fan, but other models have been known to make odd sounds when it gets stuck.

Also the Magnetron cavity cover can track across and cause the same symptoms you are describing.

As mentioned above, the Magnetron could also be faulty.

No stirrer but yeah i may have to take the cover off. A bit of a pain because of the location that is why i did not do it yet.

 

[MrAl]

Factory workers are notorious for playing pranks on each other it makes the work day more fun. People where I worked use to throw a paper clip into some ones paper lunch bags when they put there whole lunch bag into the lunch room microwave it made popping sounds then catch on fire in about 3 seconds. LOL.

Some paper food packages are laminated with aluminum foil hidden between 2 layers of paper the package makes popping & cracking sounds in the microwave. If your heating something in the original factory package try heating it in a different package. Look see if package says it is microwaveable.

Sometimes factory workers stuff their used lunch bag trash inside the produces the factory makes and sells home owner never knows what is hidden inside places they can not see. There could be something hidden in your microwave wave guide like a paper clip or piece of wire.

There is a plastic or glass wave guide cover in your microwave remove it look see what you can find inside the wave guide. It is also possible the high voltage transformer has a defect it could be sparking. Put 1 end of a 2 foot long rubber hose in 1 ear move the other end of hose around the microwave to listen for the sound you hear. Hose makes it easy to locate strange sounds. You might need to remove the oven case to listen inside.

Look inside the microwave fan for paper or plastic wrappers.

I like the idea of the rubber hose make shift stethoscope. I may tried that if i cant located it immediately.

I think maybe this sounds more like a metal box with little stones in it being shaken around. It goes on and off though it is not continuous. Like it will make the noise for two seconds, then three seconds off, then maybe 1 second on, then four seconds off, random like that so it does not sync with the turntable motion either.

 

[gary350]

And as time goes by, they are up in arms because the factory has closed, they are on the dole, and production has moved to China (other low labour cost locations are available).

Someone said: "Make America great again".

JimB

How many people remember when Ronald Reagan was president and Air Traffic Controllers went on strike for a month. After that 2 weeks later Teamsters went on strike for a month and store shelves were empty for a month. Ronald Reagan got on nation wide TV and said, UNIONS will NEVER do that to this country EVER again. Guess who signed Free trade with China and put $85 per hour unions workers in the permanent unemployment line. LOL. Greedy Unions did it to them self. Our country does not have very much industry anymore, now it is made in China. We will be in big trouble if there is ever another world war.

 

[atferrari]

A couple weeks ago my microwave oven started making noises like a Geiger Counter detecting a small amount of radiation (slow but constant low frequency click that is sort of garbled.

I read this on the web so far:
" If your microwave is making noises like a Geiger counter, the sound is coming from the magnetron that produces the microwaves. The sound is normal and there's no reason to be alarmed. If your microwave makes noises when it's in standby that are somewhat loud or strange, something could be wrong with your fan run on. "

But this sound never came out of it before about two weeks ago and i had it for at least 2 years now.

Any ideas?

Thanks.

Now I finally vaguely remembered where I've seen something similar. It was in the control panel of a Decca radar in our vessel (talking of a model of more than 40, maybe 50 years ago). Not sure if the PSU, whatever that could be. Even if located inside the bridge, lot of equipment in vessels ended with the circuitry affected, I presume by the marine environment.

I am sure your kitchen is not in high seas, but...

 

[LegoTekFan486]

Before you attempt to open a microwave oven, be aware that there's a high voltage capacitor that can hold a charge after you've unplugged the machine. With the oven unplugged, the first thing you should do after opening the cover, is to discharge the high voltage capacitor. Discharge it even if you're not planning on dealing with the high voltage section: That way, if you accidentally brush up against it, it won't matter because it's discharged.

Okay, now that the high voltage capacitor is discharged, we can start looking.

The first thing to check is the cooling fan(s). Obviously, if they're dusty, clean them. Spin them by hand and see if they feel gritty or tight. If they do, the ball bearings are either going bad, or you may need to just give it a drop or two of oil on the motor shaft. If it gets noisy again in a short amount of time, then it's time to get a new fan.

The turntable mechanism is another possible source of repetitive clicking noises. It's most likely a gearbox with the motor attached. I'm not sure if there would be a non-destructive way to access the motor shaft in one of these, that may depend on the brand.

The high voltage for the magnetron (between 2000 to 4000 volts) could be repeatedly arcing to something, but I would think you would smell ozone or burning if that were the case. If there were some sort of contamination in just the wrong place around the high voltage connections, that could lead to arcing. Is it cooking well like it did before? If not, you may have a high voltage problem. Troubleshooting that will be difficult since even if you had a high voltage probe, most likely all you'd see when the arc occurred is a voltage drop. On the other hand, whatever is arcing is likely to look burnt or damaged. If the transformer has gone bad, then the arcing will probably get more frequent with use/time and eventually the transformer won't work at all.

 

[MrAl]

Before you attempt to open a microwave oven, be aware that there's a high voltage capacitor that can hold a charge after you've unplugged the machine. With the oven unplugged, the first thing you should do after opening the cover, is to discharge the high voltage capacitor. Discharge it even if you're not planning on dealing with the high voltage section: That way, if you accidentally brush up against it, it won't matter because it's discharged.

Okay, now that the high voltage capacitor is discharged, we can start looking.

The first thing to check is the cooling fan(s). Obviously, if they're dusty, clean them. Spin them by hand and see if they feel gritty or tight. If they do, the ball bearings are either going bad, or you may need to just give it a drop or two of oil on the motor shaft. If it gets noisy again in a short amount of time, then it's time to get a new fan.

The turntable mechanism is another possible source of repetitive clicking noises. It's most likely a gearbox with the motor attached. I'm not sure if there would be a non-destructive way to access the motor shaft in one of these, that may depend on the brand.

The high voltage for the magnetron (between 2000 to 4000 volts) could be repeatedly arcing to something, but I would think you would smell ozone or burning if that were the case. If there were some sort of contamination in just the wrong place around the high voltage connections, that could lead to arcing. Is it cooking well like it did before? If not, you may have a high voltage problem. Troubleshooting that will be difficult since even if you had a high voltage probe, most likely all you'd see when the arc occurred is a voltage drop. On the other hand, whatever is arcing is likely to look burnt or damaged. If the transformer has gone bad, then the arcing will probably get more frequent with use/time and eventually the transformer won't work at all.

Thanks, and yes i am aware that there could be dangerous voltages present even after it is unplugged. I've worked on CRT televisions in the past too with the same issues.

Yes thanks for the idea about the fan i will definitely have to check that at some point.

I suspected arcing as the first possibility but when i look into the case through small slots in the case i do not see any bright flashes of light that are typical with arcing, but yes i supposed they could be somewhat hidden without the cover removed.

I suspected the turntable motor too because i had a motor go bad on me on an older microwave (it is gone now) and i took the motor apart and found that one of the windings was deteriorated due to having salt water leak down into the motor body when a container of salt water boiled over a few times in the microwave oven chamber.
I removed the few windings that were bad and resoldered the end and it worked again. That motor however stopped rotating altogether this one still rotates.
But i must say also that the 'noise' does not sync with the motor turning. It appears to occur at random times not associated with the turning angle of the platter. It could still be that i guess though but does not seem too likely.

I was thinking of using this problem as an excuse to get a new oven but i cant find one suitable for my needs. The best ones are big ones a little too big for my shelf i like to put it on.

 

[Nigel Goodwin]

Thanks, and yes i am aware that there could be dangerous voltages present even after it is unplugged. I've worked on CRT televisions in the past too with the same issues.

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.

Yes thanks for the idea about the fan i will definitely have to check that at some point.

I suspected arcing as the first possibility but when i look into the case through small slots in the case i do not see any bright flashes of light that are typical with arcing, but yes i supposed they could be somewhat hidden without the cover removed.

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).