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PC power supply fail after power a power outage

Discussion in 'Troubleshooting and Repair' started by tedstruk, Nov 30, 2016.

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  1. tedstruk

    tedstruk

    475
    7
    Jan 7, 2012
    I have a strong running Dell small factor desktop power supply that went through a power outage and now the fan doesn't run and the PC won't turn on. So I pulled it out, it's a 250w BEST and SATA in a long box... this is my first SATA repair, and as I would assume it is probably not much different, just series instead of parallel.

    Are there any standard procedures I should follow before I test it with my o-scope,?

    Where would be a good place to start checking for problems?
     
  2. tedstruk

    tedstruk

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    7
    Jan 7, 2012
    Is there a switch point that turns it on? never mind... I will just probe araound and see shat I can find!!!
     
  3. tedstruk

    tedstruk

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    Jan 7, 2012
    sitchyayshun....

    The fan stutters on power on, trys to start, no power on, and all the signals are low, 3 red wires read 2 volts, the rest are way down .8 and lower. Whats my problem???
     
  4. davenn

    davenn Moderator

    13,589
    1,872
    Sep 5, 2009
    have you tested all the output rails 12V, -12V, 5V 3.3V ?
    are any of them working ?
    The fan generally comes off the 12V rail

    have you connected the POWER_ON wire to 0V ? ... often a green or purple wire
    are the cable connections marked on the PSU ... it may tell you which wire if the power on one
    The PSU wot start up without doing that

    is .... it's a 250w BEST the PSU brand name?

    if not what is the brand name and or model ?
     
    Last edited: Dec 1, 2016
  5. Bluejets

    Bluejets

    4,062
    848
    Oct 5, 2014
    Units such as this usually wait for a pg (power good) signal from the pc.
     
  6. davenn

    davenn Moderator

    13,589
    1,872
    Sep 5, 2009
    yeah ... power on aka power good ... take your pic :)
     
  7. jvdbossc

    jvdbossc

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    0
    Jan 27, 2012
    I am not an expert, but already saved a few of pc's just by looking at the caps. In a lot of designs they are relied upon and fail. A lot of times you can see that they bulge or leak, or you get the "rotten fish smell". I would stop with powering it on and find the fault first.
     
  8. tedstruk

    tedstruk

    475
    7
    Jan 7, 2012
    melted insulation on this coil?
     

    Attached Files:

  9. tedstruk

    tedstruk

    475
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    Jan 7, 2012
    This is a good one!
     

    Attached Files:

  10. tedstruk

    tedstruk

    475
    7
    Jan 7, 2012
    The importance of fusing and breakers.... what kind and what size of fuse do I put in a PC power supply?
     
  11. tedstruk

    tedstruk

    475
    7
    Jan 7, 2012
    Got it out of there! Now how do I replace it!
     

    Attached Files:

  12. tedstruk

    tedstruk

    475
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    Jan 7, 2012
    there are 3 sizes of wire on this induction coil, and I forgot where each of them connect.... thats OK, I have ordered a new supply unit(PSU?) this is more like a project now!... can I use telephone wire to rewrap the coil?(wrong gauge is the wrong induction. What if I only need a couple feet of each?
     

    Attached Files:

  13. tedstruk

    tedstruk

    475
    7
    Jan 7, 2012
    There! thats better.. now back to my first question.... anything I should know before I hook it up to my o-scope?
     

    Attached Files:

  14. tedstruk

    tedstruk

    475
    7
    Jan 7, 2012
    Part 4. Testing...
    Hay Harv.... wanna plug that power supply in for me!
     

    Attached Files:

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