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Thread: Measure Transformers Output Voltage

  1. #1
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    Default Measure Transformers Output Voltage

    I am tearing apart my 40 watt RGB LED light source which does not work - even after multiple support tries from a Aliexpress vendor.
    How can I tell what the output voltage is of the power transformer?

    110 volts in and two same color wires coming out. Are the both voltages and I do need to check them to ground to find the voltage out?

  2. #2
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    Default Re: Measure Transformers Output Voltage

    If it really is a transformer, then it is an AC output. An AC voltmeter will tell you the voltage. If it is really a DC output then a DC voltmeter will tell you the voltage. A negative voltage tells you have the wires backward.


    2018 - Moving and going to visit my Daughter in New Zealand. Most likely I will be dark or nearly dark, Some static stuff that is simple to put up.

  3. #3
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    Default Re: Measure Transformers Output Voltage

    If you can identify what terminals are the output then you would put your meter in a DC voltage setting then place the leads on the two output terminals not to ground. It should by V+ & V- Ground will be for the AC side.

    Posting a picture of what you're looking at would be helpful.

  4. #4
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    Default Re: Measure Transformers Output Voltage

    to what Martin said, if it is a transformer then you would have AC in and out, if it is a power supply you would have AC in and DC out. Make sense?

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    Default Re: Measure Transformers Output Voltage

    Quote Originally Posted by JCook View Post
    If you can identify what terminals are the output then you would put your meter in a DC voltage setting then place the leads on the two output terminals not to ground. It should by V+ & V- Ground will be for the AC side.

    Posting a picture of what you're looking at would be helpful.
    Always start measuring AC. You would not wreck your voltmeter measuring DC when the meter is set to AC. Some meters have a tough time with AC when the meter is set to DC.


    2018 - Moving and going to visit my Daughter in New Zealand. Most likely I will be dark or nearly dark, Some static stuff that is simple to put up.

  6. #6
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    Default Re: Measure Transformers Output Voltage

    If the "transformer" is very light weight we could be talking about a switchmode power supply. If this is the case there may be a shock hazard in measuring the output. A picture would be good first.
    www.da-share.com

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