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Help! Magnetron in microwave oven makes jackhammer noise.

My microwave oven was out of order, it kept blowing up the power fuse; finally the trouble was traced to the power capacitor that was shorted.

So, the power capacity was changed and the oven worked again, but now the magnetron becomes noisy with a jackhammer noise when it is working.

This noise starts when the magnetron starts working, but it stops after some two minutes while it continues to work up to the time adjusted for it to finish its operation.

What has happened to the magnetron?
Is it possible to fix it?

On the other hand, it is my best suspicion that it is the magnetron that is making the noise and not the transformer.
What is your experience in this situation?


This is exactly the sound (click on the link below) I am getting from my microwave oven, but it does not go and on until the machine turns off; the sound stops some two minutes into the operation, and the remaining time there is no longer the sound or noise – for the remaining time it keeps ‘quiet’ up to the completion of the time period it has been adjusted to operate, or I turn the switch knob to off.
https://www.youtube.com/watch?v=CF0RXKF4puQ



Thanks for any help or information.

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Marius de Jess (author) 2 years ago

This is to report my latest finding on the annoying jackhammer noise from my repaired microwave oven.

The noise subsides within less than 2 minutes from start of operation, so I got the idea that it is the increased heat temperature within the working internal environment of the oven, that heat suppresses the noise, while the magnetron continues to work up to the complete of the period it has been adjusted to operate.

Yesterday I thought that if I start the oven again for another task to cook something while it is still hot, I mean the inside environment, then there should be no jackhammer noise.

This idea turned out to be true: so if I can install a pre-heating component to heat up the inside environment of the oven prior to the start of operation of the magnetron, then there should be no jackhammer noise when the magnetron gets started..

That means putting inside a heat coil that will work to heat up the inside environment, which will also heat up all the components inside in particular the magnetron, then when the inside temperature has reached the required heat intensity the magnetron will turn on, and there will be no more noise from the magnetron, of the annoying jackhammer kind.

That requires an electrical heat design engineer, or someone with a hobby for modifying kitchen heat appliances and fully experienced with modification of such equipment.

Right now, I am waiting for my microwave oven to do a self-rehab process on itself, namely, that the noise will completely subside in time.

As of the present it lasts only for less than 2 minutes; so the whatever things inside causing the noise will eventually get self-adjusted as to no longer get noisy.

I recall some years back I got a car starter motor changed with a new bushing ring because the old one had gotten overly widened so that the motor shaft was no longer well-centered -- which made the shaft rotation difficult and even prevented it from rotating at all.

When the new bushing ring was installed, at the start it caused a screeching noise which eventually subsided: because the new bushing ring had gotten adequately widened so that the rotation was smooth and noiseless.

See,

https://www.instructables.com/id/Starter-Motor-Repa...

If you are now sure the sound does not come from the magnetron or transformer I would still take the cover off and test where the noise is coming from.
If something is slightly loose the heat might fix the problem by expanding, if you fix it properly it will always be silent.

You can also get a sheet of car sound proofing material, the black tar like stuff with one sticky side, similar stuff can be found in the home depot store for the use on stainless steel kitchen sinks.

Put it on all surefaces that have no holes and there should be no more vibration ;)
And heating is not the best idea as you introduce metal to the inside of the microwave - unless you desire a lot of sparks and lightning don't do it ;)

Marius de Jess (author) 2 years ago

Thanks Downunder35m for your concern.

I have been observing and listening to this noise, and I have noticed that the noise gets weaker until finally some two minutes into operation, it is no longer annoying but has become similar to the previous quality and volume of the operation sound of the oven, prior to as when the oven was working normally -- until it broke down and I fixed it with replacing the power capacitor.

So, I suspect that the noise is related to the heat temperature of the oven which covers also the heat temperature of the magnetron and every component of the oven.

When the heat gets to a higher degree some two minutes into operation, the noise subsides to what I might call status of non-annoyance and is even no longer noticeable to anyone, should he comes to the scene who was not present when the oven started operating.

I think that with more time in operation of the oven, a condition will eventually come about that the noise will no longer be annoying hence not noticeable -- because the machine could have then self-adjusted itself to work without the jackhammer noise -- some kind of self-rehab by itself, hahahaha.

Everything else with the oven is functioning satisfactorily.

I will submit further reports on this matter.

Hmmm, could it be as easy as vibrations from a completly different source?

I mean the trnsformer always causes massive vibrations transfered to the entire structure of the oven.

I assume you replaced the capacitor with one of the same rating?

Keep us informed if you find something.

There is only one reason for the noise : Vibration.
There are only two sources for it : Magnetron and transformer (except you have loose stuff around those parts).

Take the cover off to check where the noise is coming from, you don't have to be concerned about radiation as this will stay inside the cooking area.

If it is the transformer: Unscrew and place a thin piece of rubber under it, fasten the screws again.

If it is the magnetron check if one of the magnets became loose or if the magnetron itself is loose.

The magnet can be fixed with some good glue, like shoe glue, but you might have to lift it a bit to get the glue under the magnet.

If it is the magnetron itself check the mounting screws.

Marius de Jess (author)  Downunder35m2 years ago

Thanks, Downunder35m.

Any information on how to dismantle a magnetron?

Please read my idea below, sent to GE Appliances:

Please read the quote as follows.

[QUOTE BEGINS]

[Quote begins]

http://www.geappliances.com/search/fast/infobase/1...

Microwave - Normal Operational Characteristics for a
Microwave

It is normal to experience any of the following with a
microwave oven:

[...]

Dull thumping
sound or hum while cooking at power levels other than high.

When using a power
level other than HIGH or 10 the magnetron tube cycles on and off to obtain the
lower power. This cycling of the magnetron tube causes this dull thumping, pulsating,
or humming noise. When combination cooking in microwave/convection models, the
cycling of the convection element and fan will alternate continuously with the
hum of the magnetron and the fan.

[...]

[Quote ends]

What do you mean by power cycle, high and low, so that low
power cycles can cause noise while high power cycles will not.

What I know is that high power or low power cycles depend
upon how long in time period the magnetron is working and how long in time
period it stops working until the next period of work to be interrupted again
by the period of non-work; and the joined period of work and of non-work is set
by the human operator using the power knob or button.

My problem is the following:

Power is set at maximum – no interruption of work for magnetron: for the first 2 minutes
more or less of magnetron operation it emits a jackhammer noise which stops at
the end of the 2 minutes period, and the magnetron continues to operate
'quietly' until it stops at the completion of the adjusted operation period or
I turn it off.

This microwave oven is not digital but mechanical in its
control, it had been in service for over 7 years. It started blowing up the
power fuse, and upon changing the power capacitor the normal function was
restored and it works as before except for the noise which was not present
before.

Please suggest some solutions; I notice that it seems the
magnetron now needs to get heated up before the noise will go away.

Please ask your engineers to investigate the mechanics and physics
of heat and noise and vibration in the operation of perhaps an overly aged
magnetron.

Thanks in advance for your reply by email.

My email: mdejess@gmail.com

[QUOTE ENDS]

Dismatling them is pretty straight forward, but most are clamped together which means you have a hard time getting it al aligned again.

If the magnets use heat glue you can put the magnetron in the oven at around 150° celsius for 10-15 minutes (pre-heated otherwise a bit longer).

However it might be easier to get a magnetron from the scrap yard.

The capacitor is matched for the transformer (acts as a voltage doubler with the diode) so it will work with a replacement as long as it is in a similar power rating.

E.g. a 900W model will still do fine in a 100W microwave but a 1100W model won't do you good in a 700W mircrowave.

If in doubt you can replace the lot, capacitor, transformer and magnetron from a scrap model.

I have done it a few times and "upgraded" mine this way from a 900W standard model to a stainless stell one with convection and grill ;)

(Always keeping the better model and replacing the broken parts from another one)