9V Transformer is Buzzing - Need I Worry?

I have a 9VAC GE security system transformer that began to make a faint buzzing sound and I'm worried this may be unsafe. The noise started a week ago after several weeks of it *not* buzzing when first installed - or at least I never noticed it. The unit does *not* appear "hot".

I changed the receptacle that it is plugged into and checked for grounding and it is properly grounded. I tested the voltage for 110v with a multimeter and it is steady at 110. I also swapped the transformer with a new one but it still buzzes. Finally, I ran the transformer to another two outlets and it buzzed on both, but each with different intensity.

What could be the cause of this, and how do I fix it? Is this a warning that it should not be used or corrected?

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The buzzing is almost always a loose lamination (the iron part of the transformer) and is usually harmless.

If you want to fix it, here is how. Find a shop that rebuilds electric motors and has a varnish tank. Ask them to dip the transformer for fifteen minutes, or when it stops bubbling. You can ask them to bake it, or you can take the sticky mess home, bake it in the oven for three hours at 300 degrees F, and listen to complaints about the smell.

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Guy Macon

That'll dang sure do it. Another thought is to ring up my favorite surplus company (mpja.com) and get another for less than $10. Use 'ol buzzy for a paperweight.

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Steve Cothran

Its called a hysteresis hum caused by loose laminations I would replace it cheap enough to do Not likely to happen but it could cause the insulation coating on the windings to deteriate causing a short circuit.And please don't correct my spelling

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A loose lamination is the likely cause. You can fix it:

Warm the sucker up to ~220 F, dip it in a can of varnish or oil base paint for a few minutes and hang it to air dry.

Don't exceed 250 when you heat it, let it soak at temperature for a time. Practice fire safety while dipping it, do it outdoors.

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