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  1. #1

    Question 12 volt transformer

    Good Morning- I have a question regarding a 12 volt transformer I'm hoping some one can help with. I'm trying to repair a low voltage lamp that is no the blink. I found the 110 to 12 volt transformer in the base of the lamp
    and proceeded to test it. I found 110 going into the transformer but nothing coming out the 12 side. I assumed the the transformer was bad so I ordered the exact same transformer from an electrical supply house. When the new one arrived I bench tested it only to find the same behavior. 110 going in but no 12 volts going out ? Am I missing something here or did I get a bad unit ?

    Best Regards
    Snafu34

  2. #2
    Electrical Contractor/Instructor jwelectric's Avatar
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    It is possible that you got a bad transformer form the supply house.

    If a voltage is applied to the primary then there should be a voltage present on the secondary

  3. #3
    Jack of all trades frenchie's Avatar
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    Not sure this is relevant, but most transformers like that also go from 120 AC to 12v DC. Your tester should have different settings for AC and DC, make sure you're on the right setting... ?

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    Whoa, there, a simple transformer doesn't work on DC...it will only work on a/c in and produce a/c out. Now, there could be a rectifier circuit somewhere on the output generating DC voltage, but that is totally independent of the transformer. If the black box has a transformer in it, it could be a hybrid circuit with a rectifier.

    When you measured, where did you do it? At the light socket? at the output of the transformer? Sometimes, there is an in-line fuse or fuseable link, all it may take is a new one of them. It could be soldered in and may not be obvious.

    With the thing unplugged, do some continuity checks of the primary, secondary, and from the secondary to the lamp socket. You may just find an open. If you didn't actually measure on the input wires to the transformer, it could be the switch as well.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    Jack of all trades frenchie's Avatar
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    Well, I did say "most"...

    Snafu34, check the label on the transformer, make sure it matches up with your tester setting.

    All I was saying...

  6. #6

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    Thanks for looking gentlemen-

    The transformer is a WH-1501E6A
    AC 120V -60Hz 1.2A
    AC 12 V 150W output
    Auto reset - soft start
    overload protected.
    For 12 Volt Halogen lights only.
    hxxp://www.atlantalightbulbs.com/ecart/nw012104/WANGWH-1501E6A.htm
    (change hxxp to http)

    The transformer has two lines in for the 120 side
    and two out for the AC 12 out

    I connect the transformer to 110/120 and confirm it is getting power
    but yet there is NO reading on my voltmeter on the output 12 volt AC side.
    My meter is a cheapie that only has AC setting of 200 and 600 volts
    but I think it should show the 12 Volts anyway------- correct ?

    THX
    Snafu34

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