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Wall Transformer Gone Bad?

Discussion in 'Electronic Design' started by VHarris, Nov 4, 2005.

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  1. VHarris

    VHarris Guest

    I have a 120v AC Class 2 Power Supply that is rated 12v 500mA DC
    output. On the voltmeter, its output is ~20.4 volts. What typically
    goes bad that causes such a high spike in the output voltage?
  2. Phil Allison

    Phil Allison Guest


    ** Connect a 24 ohm ( 6 watt rated ) load.

    See what happens.

    ............. Phil
  3. VHarris

    VHarris Guest

    I don't have a 24 ohm load, but I connected a 150 ohm load and the
    voltage across the leads dropped to 17.3 volts.
  4. Phil Allison

    Phil Allison Guest

    ** Learn how to post.

    The learn ohm's law.

    .......... Phil
  5. Pooh Bear

    Pooh Bear Guest


    So the wallwart is fine.

  6. John Fields

    John Fields Guest

  7. Phil Allison

    Phil Allison Guest

    "John Fields"

    ** Yawn.

    ** A nice cover story.

    ......... Phil
  8. Fred Bloggs

    Fred Bloggs Guest

    How does the AC power supply have a DC current rating? You mean it is
    120VAC input with 12VDC @ 500mA output. This power supply is
    unregulated, it's only function is line step-down, rectification, and
    some filtering. The output DC voltage will be a function of loading,
    settling to 12VDC with 500mA of current draw. If you need 12VDC at
    lesser current, you will have to add an external regulator, or buy one
    that has the word "regulated" on the label.
  9. kell

    kell Guest

    Or put an extra load resistor in parallel with the load you want to
    run, that will bring the voltage down.
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