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Power supply lost -5 volts

Discussion in 'Troubleshooting and Repair' started by chuppyh, Oct 9, 2013.

  1. chuppyh

    chuppyh

    3
    0
    Oct 8, 2013
    I've checked with my checker I've lost -5 what would cause it how do I fix?
    Would it be a diode are a resistor
     
  2. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,266
    Nov 28, 2011
    It's a diode. The third one from the left. LOL

    What kind of power supply is it?
    Can you post some photos of the main circuit board?
     
  3. chuppyh

    chuppyh

    3
    0
    Oct 8, 2013
    Picture

    Dell 5251
     

    Attached Files:

  4. chuppyh

    chuppyh

    3
    0
    Oct 8, 2013
    Pic 2

    Ps 5251
     

    Attached Files:

  5. Claas

    Claas

    4
    0
    Oct 1, 2013
    Is there 7905 negative voltage regulator on there? I
     
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,266
    Nov 28, 2011
    Follow the -5V wire back to the board and trace the track. It may go to a 7905 regulator as Claas suggested, or it may be supplied from a winding on the main transformer via a diode. Check for broken tracks, dry joints, and broken joints, and VERY CAREFULLY check the pin voltages on the 7905 if there is one.

    Have a look at some general schematics for PC power supplies. You will be able to see how the -5V rail is generated.
     
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