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When a power brick is humming is that a bad thing? What does it mean.

Does having it plugged into the wall directly or in a UPS or in a daisy chain of power strips make a difference

marked as duplicate by Xavierjazz, Ƭᴇcʜιᴇ007, DavidPostill, fixer1234, mdpc Feb 16 '15 at 6:42

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    Might be as simple as the layers making up the iron core not being properly fastened together. If that's it, there would be little impairment to its function, merely irritation at the noise. Only way to find out would be split it open - which might do more harm than good. – Tetsujin Feb 15 '15 at 17:07
  • You asked us a question that only you can answer. A humming is not bad or good it just means there is an electron leak ( say a weak capacitor ) or something like that. – Ramhound Feb 15 '15 at 17:08
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    Yes, UPSs make quite a lot of difference. I once plugged a fan into my UPS to test it. I never knew a plain AC motor could make such disturbing noises. – Daniel B Feb 15 '15 at 17:09
  • It seems like the easiest way to answer your second question is to do it and see what happens. – fixer1234 Feb 16 '15 at 1:39
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If the power supply is not getting hot, there's probably no reason for concern:

As mentioned above by @Tetsujin and @Daniel B, the two most likely causes are loosening of the laminations of a transformer and the square-wave output of some UPS's. Since neither is significant, the noise can be ignored as long as the appliance works.

If you have a basis for comparison, you could make a judgement: if the power supply draws more current from the mains than before, or if there is AC leakage, as shown by an oscilloscope or audio amp, on the DC output, there might be some reason for concern.

Do not cover the noisy power supply in an attempt to make is quiet, though, as that might cause it to overheat.

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