High pitch sound from psu. No output voltage.

Discussion in 'General Electronics Chat' started by arthur92710, Feb 12, 2008.

  1. arthur92710

    Thread Starter Active Member

    Jun 25, 2007
    307
    1
    I was looking for various voltages on a psu then it started making a high pitch sound and the outputs had no voltage.

    heres a photo of the psu. By the way its from a PS2

    I found the board on ebay for $10, so if the cost to fix it is higher I would get a new one but i would like to fix this one.
     
  2. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    That's a tough one! The high pitch noise is definitely from the switching device and/or the flyback transformer. It's a bit tough to diagnose though, I would check if the windings are a dead short or open. If there is some resistance there, then chances are it is okay. If the transformer is okay, then I would replace the FET or the diodes on the heatsink.

    goodluck

    Steve
     
  3. arthur92710

    Thread Starter Active Member

    Jun 25, 2007
    307
    1
    Ill be right back ill test the transformer.
     
  4. arthur92710

    Thread Starter Active Member

    Jun 25, 2007
    307
    1
    Its the big transformer. When you apply pressure to it the sound changes. It you touch anything else it does not.

    How could the transformer die like this? All i did was put the black wire from the fan on ground and the red one onto various points on the dc side.

    Should I get a new board?
     
  5. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    Your meter is extremely high impedance, there should be no resistive loading on the circuit from it at all. Whenever electronics is sensitive to touch, that usually means the added capacitance is being picked up.

    You should measure the resistance of the winding when the circuit is shut off. This will let you know if your transformer has an open winding, which is very possible given how these units are made.

    Your voltage is probably AC, so you may not have any luck measuring DC. The dual diodes along with the probability of many connections on the secondary of the transformer leads me to believe that it is a full-wave flyback typology.

    So, just check out the transformer, if it is dead, then it is pretty much game over for that board. If it isn't, then I would tend to think it is either switching device, because of the noise involved and the low-reliability of these compared to the other components on board.

    Steve
     
  6. arthur92710

    Thread Starter Active Member

    Jun 25, 2007
    307
    1
    Its defiantly the transformer, Ill order a new board and "fix" this one(yay high voltage cap!)
     
  7. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    How did you come to that conclusion? Was it open circuited? Yes! The caps on those boards are $$$ :)

    Steve
     
  8. arthur92710

    Thread Starter Active Member

    Jun 25, 2007
    307
    1
    Thanks for your help guys but I got one off of ebay for $5 so its fine.
     
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