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zx3chris 19th May 2003 05:00 PM

what causes a transformer to buzz
the wall mount ad-dc transformer for my cordless phone started buzzing today---does this mean its on its way out?? i know why flourescents and incandescants and dimmers buzz sometimes, but why a tranny???


RobM 19th May 2003 05:10 PM

Usually because the windings are vibrating against each other.

KevinLee 19th May 2003 05:13 PM

Hello ZX3Chris,

Transformers have many windings wrapped around a metal or ferrite core. During manufacturing these windings are dipped in varnish or a similiar material to stop the individual windings from buzzing/humming/ringing.

It is possible that the varnish like material is breaking down on the windings, a shorted transformer is likely in your future.



zx3chris 19th May 2003 06:17 PM

makes sense now--thank u


KevinLee 19th May 2003 06:20 PM


I have stopped buzzing in transformers by spreading some silicone on the loose windings with my finger and letting it set up for 24 hours.

This will not always work but it will work most of the time. Oh yeah, make sure it is unplugged first.


PMiczek 19th May 2003 06:46 PM

If this is a sealed wall-wart type, and if it did not buzz before, I suggest checking for overheating before attempting any kind of fix. In other words, it could be buzzing because heat may have broken down the basic construction of the transformer, and you could be running a chance of a fire, small as it is. (wall-supplies are cheaper to replace than houses).

KevinLee 19th May 2003 07:33 PM


Very good point on the safety issue.

I would not suggest the above fix unless the diy-er is sure it is only loose windings not another problem.


Fred Dieckmann 19th May 2003 08:27 PM

The buzz on transformers......
Maybe a bee or some other flying bug crawled into the housing. As likely an explantion as some I have read here.

RobM 19th May 2003 08:32 PM

The three reasons I can think of for a transformer to emit noise:

1) Loose windings vibrating
2) Core delamination, causing laminations to vibrate together
3) Magnetostriction in the core (the metal of the core deforming under the magnetic forces)

PMiczek 19th May 2003 08:51 PM

Transformer hum

Have any other explanations that would apply to a small wall transformer & DC converter?

(I've heard "it hums because it does not know the words already")

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