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How to identify transformer output

Discussion in 'General Electronics Discussion' started by vinod chandran, Apr 24, 2013.

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  1. vinod chandran

    vinod chandran

    192
    2
    Jun 21, 2011
    Hi there,
    I have an unknown transformer salvaged from an old vcd player. i need to connect it in my amp. So i checked it with a DMM. The secondary of the transformer has 4 pairs of wires. 2 green, 2 black, 2 white and 2 yellow.
    This is the results.
    2 green-10.9v
    2 black- 18.0v
    2 white- 10.9v
    2 yellow- 3.2v
    My question is, How to find negative voltage from this output. because this transformer is connected with a dual power supply in that old vcd player. So this transformer might have a 10-0-10 output. How to find that wires from this transformer.? Please help.
     
  2. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    Check first to see of any of the windings are connected together. Most likely they are not. You could then use the two 10.9V windings. Connect one of the leads of each together and measure across the other 2. If you read 21.8V then you have them connected correctly. Otherwise use the other lead one of the pairs for the common. Now you have a 10-0-10.

    Bob
     
  3. vinod chandran

    vinod chandran

    192
    2
    Jun 21, 2011
    Hi BobK,
    Thank you for the reply. But there was spark when i connected two wires of same colour.
     
  4. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    I meant to connect one of the green wires to one of the white wires. But before you do this, make sure that a green and a white are not already connected by checking the resistance between them (with the transformer not powered.) If you do this, you whould measure either 0V or 21.8V between the other green and white. If you mesure 0V, swap the green wires of the pair that are connected together. Once you see 21.8V across the other green and white, you have a 10.8-0-10.8 transformer with the green/white that are connected being the common.

    Bob
     
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