Originally Posted by Ganglin
Andy, Merry Christmas. How is this done...?
Take the transformer out of the univolt.
Get a pint or quart of high temp paint.
Put the transformer in a small container, and pour the paint over the transformer.
Gently shake the container so as to remove any bubbles that may form, or invert the transformer, or both, several times.
Let the transformer soak, for at least a day, if you can.
Remove the transformer, let it drip dry, then reinstall it in the univolt.
The noise will be gone.
Loose laminations cause the hum, since they will be ever so slightly moving when power is applied.
You will fill the voids between the laminations with the pint.
Or, get some cheap earplugs.