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Faulty power supply

Discussion in 'Troubleshooting and Repair' started by Michael black, Aug 31, 2016.

  1. Michael black

    Michael black

    5
    0
    Jul 7, 2015
    hi all bought a cople of power supplies of eBay (they were cheap honest) They both have the same fault that the voltage from the outputs don't match the marked voltage. This doesn't bother me too much I can use a multimeter to ensure I have the voltage required. The main problem is it's a 130 VA supply but at 12V and 2A the voltage drops off. Looking inside the power supply it's a transformer with 3 tappings and 4 relays change the voltage for the ac output, the DC output is a bridge rectifier straight from AC to DC.
    The centre circle on the board is where the rotary switch goes.



    image.jpeg image.jpeg image.jpeg what in the circuit can caus that fault
     
  2. ModemHead

    ModemHead

    69
    20
    Dec 2, 2010
    The orange wire on the left has broken off the PCB.
     
  3. davenn

    davenn Moderator

    13,289
    1,756
    Sep 5, 2009
    more precisely ... the orange wire on the left in the top photo

    the one on the right in the bottom photo looks OK



    Dave
     
  4. Herschel Peeler

    Herschel Peeler

    401
    65
    Feb 21, 2016
    I don't see the capability of 130 VA on that board. The TO-220 case in the lower left corner ... is it an LM317?
    Otherwise a nice looking power supply.
     
  5. davenn

    davenn Moderator

    13,289
    1,756
    Sep 5, 2009

    no, a 7805
     
  6. Bluejets

    Bluejets

    3,478
    705
    Oct 5, 2014
    • A 240V input power supply with adjustable output in 1 volt increments
    • Output voltage variable by rotary control knob up to 13V
    • Continuously rated output of 8.5A, AC or DC

      Note on the bottom of the unit .......

      The internal transformer is protected by a thermal trip. This will not operate in normal use but should the instrument become excessively hot, the trip will temporarily cut-off the output.
    Philip Harris model No. G83458
     
  7. Michael black

    Michael black

    5
    0
    Jul 7, 2015
    Thanks for the replies guys the orange wire has been removed from the board to test its the thermal trip and is not open circuit. The supply works in a fashion boil won't give out the power it should. Any ideas?

    Mick
     
  8. Bluejets

    Bluejets

    3,478
    705
    Oct 5, 2014
    I'd start by testing the output of the transformer.
     
  9. Nemo1956

    Nemo1956

    34
    7
    Sep 5, 2016
    Wow it goes to 13. I was under the impression they only go to 11.LOL
     
  10. Bluejets

    Bluejets

    3,478
    705
    Oct 5, 2014
    Sorry but miss your point.
    Spec says 13 and so does 2nd photo in post #1.
     
  11. Nemo1956

    Nemo1956

    34
    7
    Sep 5, 2016
    No this comment is really intended for an amplifier If you have seen the the film you would have understood the comment.
    It'sjust for fun.
     
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