12VAC adapter reads aprox. 24VAC

Discussion in 'Power Electronics' started by iONic, Dec 15, 2016.

  1. iONic

    Thread Starter AAC Fanatic!

    Nov 16, 2007
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    Just had an AC adapter send to my father place to replace a bad one that runs his Christmas tree lights. the old one was spec'd at:
    INPUT: 120VAC
    OUTPUT: 12VAC, 1000mA

    The new one, seen in the link below, is spec'd the same, but reading about 24V on his analog multi-meter.

    Is this normal for one without being under load??
    Should I try it or send it back?

    https://www.amazon.com/gp/product/B00417WE2K/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
     
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    Yes its the same rating and voltage is DC.
     
    Last edited: Dec 15, 2016
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
    15,853
    4,628
    No doubt a ordinary transformer, they usually rate them for the voltage at the rated load, high off load is normal.
    Max.
     
  4. iONic

    Thread Starter AAC Fanatic!

    Nov 16, 2007
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    Thanks guys. The lights work (fiber-optics), but the changing colors are not working. Shouldn't be a connection to the supply. I think there is a color wheel at the base of the tree which is probably not rotating, not sure why. Will have my dad keep an eye on it.
     
  5. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
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    No, it can't be just a transformer as it is specified to run from 100V or 240V input so it really must be switch mode (it is DC output). In that case I would expect the output voltage to be close.
    Does the label on it say it is 12V?
     
  6. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
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    I just spotted this line in the description:
    "Output : 12V 1A Max (Compatible 0.3A-1A Power)"
    This is probably saying that there is a minimum load of 0.3A so that might account for the discrepancy.
     
  7. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    That's the problem, it needs an AC supply to make the synchronous motor rotate.
     
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