Damping coil noise

[Tony Houghton]

My motherboard emits a high-pitched noise, probably from one or both of
a pair of coils near the CPU. I was told this group may be able to
recommend a suitable type of "gunk" (polyurethane?) to apply to stop the
noise. TIA.

 

[John Popelish]

My motherboard emits a high-pitched noise, probably from one or both of
a pair of coils near the CPU. I was told this group may be able to
recommend a suitable type of "gunk" (polyurethane?) to apply to stop the
noise. TIA.

You may be able to reduce it a bit by coating the coil with an epoxy
or other varnish that holds the windings still (which rattle from
their magnetic fields, if they are loose), but if it is made with a
magnetic core that is magnetostrictive (changes shape when a magnetic
field passes through it) then you are probably out of luck. It is
mounted on a motherboard that is acting as a sounding board.
Replacing the inductors with ones with better cores may be the only
effective solution, and if you don't get it right, you risk damaging
the processor.

 

[Tony Houghton]

In <[email protected]>,

You may be able to reduce it a bit by coating the coil with an epoxy
or other varnish that holds the windings still (which rattle from
their magnetic fields, if they are loose), but if it is made with a
magnetic core that is magnetostrictive (changes shape when a magnetic
field passes through it) then you are probably out of luck. It is
mounted on a motherboard that is acting as a sounding board.
Replacing the inductors with ones with better cores may be the only
effective solution, and if you don't get it right, you risk damaging
the processor.

You could be right about the windings rattling, it's more of a hissing
noise than a whine.

I suppose I could see if anything like this is going to work by poking
them with something like the rubber on the end of a pencil while they're
making the noise... I heard you have to be a bit careful about what you
use on them, some materials are corrosive. I definitely don't want to
replace the coils altogether.

 

[mike]

In <[email protected]>,



You could be right about the windings rattling, it's more of a hissing
noise than a whine.

Depending on your hearing, you may not be able to tell the difference
between 15khz hiss and whine. But if it's really hissing, sounds like
you may have high voltage corona. Blow the dust out of it. If you
smoke, you've probably got gunk all over the inside that will be nearly
impossible to get off.

I've seen ceramic caps that make very efficient sound generators in this
frequency range. They're so stiff and well coupled to the board that
there ain't much you can do except change them to some type that's not
piezoelectric.

I suppose I could see if anything like this is going to work by poking
them with something like the rubber on the end of a pencil while they're
making the noise... I heard you have to be a bit careful about what you
use on them, some materials are corrosive. I definitely don't want to
replace the coils altogether.

Don't go poking around in there with a pencil. Use something completely
insulating, plastic, phenolic rod, anything but a pencil.
mike



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[Tony Houghton]

In <[email protected]>,

In <[email protected]>,

[Snip]

You could be right about the windings rattling, it's more of a hissing
noise than a whine.

Depending on your hearing, you may not be able to tell the difference
between 15khz hiss and whine. But if it's really hissing, sounds like
you may have high voltage corona. Blow the dust out of it. If you
smoke, you've probably got gunk all over the inside that will be nearly
impossible to get off.

I don't smoke, but I've had the misfortune of working inside PCs owned
by people who do. I don't think it's dust because it's been doing it
pretty much since the board was new, and I'm always amazed at how little
dust gathers in my PCs considering their environment.

I've seen ceramic caps that make very efficient sound generators in this
frequency range. They're so stiff and well coupled to the board that
there ain't much you can do except change them to some type that's not
piezoelectric.
:-(.


Don't go poking around in there with a pencil. Use something completely
insulating, plastic, phenolic rod, anything but a pencil.

Sorry, what I was actually thinking of was a 0.5mm pencil I've got, made
completely of plastic.