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Help with bench-top PSU

Discussion in 'Power Electronics' started by Kerazyugy, Nov 1, 2013.

  1. Kerazyugy

    Kerazyugy

    7
    0
    Nov 1, 2013
    hey everyone, I am trying to rig up a computer power supply to be used on a benchtop.

    I was told that by connecting pin 14 (in my case green) to ground that would tell the psu that the motherboard was connected and would work.

    so i tried it before opening up anything and it did work...

    so i proceded to connect all ground wires together into one
    and all red wires together into one
    and all yellow wires together into one....

    NOW i tried doing the same thing (note i left one ground wire seperated from the rest in order to run as the switch)

    and now when i connect the green wire to the ground the light on the back of the psu turns solid green and the fan kicks on for a split second just enough to make it halfway spin and it does nothing....

    i'm not geting any voltage from any of the wires now and i dont know what i did to cause it........

    P.S. I know very little about electronics so i'm following a tutorial on YouTube on how to do it.... but i'm stumped

    PLEASE HELP FIX MY STUPIDITY lol... thanks in advance!


    (edit) the psu is a LITEON PS-5251-08HT 250w incase that effects anything :)
     
    Last edited: Nov 1, 2013
  2. Fish4Fun

    Fish4Fun So long, and Thanks for all the Fish!

    436
    99
    Aug 27, 2013
    Yes, knowing the type of PS is important, more importantly, since this is an OEM part, and I can't seem to find it's specs, you need to take a picture or type the specifications on the label and post here.

    If I had to guess, I would assume the PS has more than one rail for the +12V (Yellow wires), and that by connecting them together you are creating a fault situation; or that you have connected the +5V Stand-by (purple wire) incorrectly, kinda hard to guess, but in any case, there is no real need to connect any wires together, simply use one of each voltage that you require and be done with it. (No harm connecting grounds, but not really much help either).

    Fish
     
  3. Kerazyugy

    Kerazyugy

    7
    0
    Nov 1, 2013
    Sweet I think you are correct! On the side if the psu it says
    +5v 25aMAX
    +3.3v 18aMAX
    +5v 2aMAX
    +12v 14aMAX
    -12v 0.8aMAX
    So if I'm ready that right it says I have 2 +5v "rails"
    I'm going to open it back up and see if I can figure out what red wire is diff and separate it from the bunch and hope it works! Thanks for the help man! Ill post if it worked
     
  4. Kerazyugy

    Kerazyugy

    7
    0
    Nov 1, 2013
    Sweet I think you are correct! On the side if the psu it says
    +5v 25aMAX
    +3.3v 18aMAX
    +5v 2aMAX
    +12v 14aMAX
    -12v 0.8aMAX
    So if I'm ready that right it says I have 2 +5v "rails"
    I'm going to open it back up and see if I can figure out what red wire is diff and separate it from the bunch and hope it works! Thanks for the help man! Ill post if it worked
     
  5. Kerazyugy

    Kerazyugy

    7
    0
    Nov 1, 2013
    Hmm.... Now that I think about it more I assume the extra +5v says sb and I think is referring to the purple wire... I'm told this wire is always got 5volts when the psu is plugged in for "wake on LAN" and stuff like that ... I disconnected the red wires From each other and it didn't work :/ guess I could disconnect them all and trial and error and find out what one is making it fault...... Just sucks cuzz I made all the wires nicely crimped already! Haha
     
  6. Kerazyugy

    Kerazyugy

    7
    0
    Nov 1, 2013
    Note I have not connected the purple wore to anything bit when i test it it has 5volts even tho the psu is off... (But still plugged in)
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,178
    2,690
    Jan 21, 2010
    You didn't connect +12V and -12V together did you?
     
  8. Kerazyugy

    Kerazyugy

    7
    0
    Nov 1, 2013
    no i did'nt.
    i put all the grounds together into one bunch
    i put all the red (+5v) wires together into one bunch
    i put all the yellow (+12v) wires together into one bunch
    i put some tape on the end of the following wires to keep from shorting
    blue -12v
    purple +5v
    pink?
    and gray.
    Then i took one gorund wire and the green wire (pin 14) and connected them as a switch.....

    BUT now i'm really confused and think i may have shorted something or screwed something up.

    i disconected all bundles so it is in exactly the same condition as i started (minus whatever i did to f' it up) and it is doing the same thing........when i connect green and black it turns on for a split second and then stops....

    so i donno what happened but i must have fried something in there guess i'll try on another psu :) good thing i have crap loads of them lol
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,178
    2,690
    Jan 21, 2010
    Try placing a load on the 5V rail (not the purple one).

    A 10 ohm 5W resistor would be my starting point.

    It is possible that without a load the output floats high and the power supply shuts down to prevent damage to voltage sensitive chips.

    The 5V output is capable of driving large loads. If you don't have the resistor, but can lay your hands on a 12V globe rated at between 5W and 25W then that might suffice. Higher wattage bulbs might be OK too, just remember it's wasted power. And yes, I said a 12V bulb on the 5V rail.
     
  10. solo2racr

    solo2racr

    142
    0
    Aug 21, 2013
    A quick search found this, if it helps.

    [​IMG]
     
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