Loud hum from doorbell transformer

Discussion in 'Electrical Forum discussion & Blog' started by pit monster, Dec 29, 2009.

  1. pit monster

    pit monster New Member

    Dec 29, 2009
    Lancaster, PA
    I just bought an 1923 home which has a neat working door bell which may be original. Anyway there is a very loud buzz originating from the transformer.

    Could it be as simple as swapping out the transformer to eliminate the hum or is there any other trouble shooting I should do first?
  2. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    When a transformer gets old, the varnish and the rivets can get loose, and the plates will hum. It can also hum or get worse if it is overloaded. But the easiest thing is to replace the xfmr and see where you are. Try to find the output voltage and a volt/amp spec. number on it somewhere, and get one with the same output voltage, and at least the same minimum V/A
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    If it humms all the time, replace it if it bothers you. If it only humms while it is under load (i.e., the doorbell is being used), it could be too small. Best to look at the doorbell itself. They usually have a VA rating on the label. If your transformer is at least that large, it will work well.
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