ATX Power supply repair help

Discussion in 'Power Electronics' started by GASANT, May 3, 2013.


    Thread Starter New Member

    Apr 30, 2012
    Hi Friends

    Can you please help clarify my problem. I am really confused.
    I am trying to fix my atx smps.

    The problem or confusion. Measurements on primary side.( hot side)
    1) I place black probe of multimeter to negative of bridge rectifier and red probe to positive of main electrolyte capacitor and get a reading of 300v which I am happy.

    2) However when I place black probe of multimeter on negative of electrolyte cap and red probe on positive of cap I get a reading of 24 v. (Same cap as no 1)

    Is this normal readings regarding atx smps.

    Thank you
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    No,you may be reading across a different capacitor in the circuit, most ATX psu's have a split capacitor setup they are in series across the supply, so they can be used as a voltage doubler when connected on low voltages, similar to this diagram.
    Last edited: May 3, 2013