Psu problems and solutions.

Discussion in 'Hardware troubles and Repair support.' started by Johnny B., Jun 23, 2015.

  1. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    1. Problem, Psu works fine but the pin 4 3.3v is always present, even without it's connected to the motherboard.
    In my case it was an Q200 Tsop23-3 issue.


    Marking code is 23 and vertical 22 further unknown.
    I had taken one from another spare board.


    2. Problem, Psu makes a hissing sound.
    It looks as if the sound is coming from the big transformer T200, or the IC101.
    In most cases it was a defective cap, the 22uF 50v C109
    This is a most common problem, often fixed with a new cap.
    Replace this with quality cap.



    3. Problem, Psu makes a hissing sound.
    In this case, it was the zener diode ZD101.


    4. The psu makes a hissing sound, or ticking sound, or only when it's switch Off it makes a noise until it's unloaded.
    But the psu is still working..
    This could also be due the 22uF 50v C109 cap.


    5. Box does nothing, when measuring the psu connector you notice that you only have the 14v, other voltages are not present, so basically it's in off state.
    By pressing the on button at the front you notice that you see a voltage on the pin 4, but still nothing else happens.
    Then it could be a defective Q200 smd transistor.

    6. 14v missing, or drops.
    Check/replace the IC100/C104/ZD101/C103/D106 Hot zone
    There is also a fragile link between the IC1oo center pin/C105 to the C104/ZD101/pin2 T100 which may be interrupted, if so make a new link between them.

    7. Psu only switched on from the main power switch, when turn off with push button on front it failed to turn on.
    Check diodes transistor IC200 and cap C603.

    More will follow later...
    Last edited: Dec 24, 2015
    toysoft and Aliraza63 like this.
  2. Miguel Angel

    Miguel Angel New Member

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