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Old pc power supply alternatives.

Discussion in 'Power Electronics' started by sureshot, Jul 8, 2012.

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  1. sureshot

    sureshot

    234
    13
    Jul 7, 2012
    Hello to you all, my first question.
    What i am trying to find an answer to is if i convert an old pc power supply can i use an alternative apart from the suggested 10 watt 10R or 5R load resistor, is it possible to trick the supply into believing its got a load on the output, i know the above resistor only uses an amp or so if 4.7 ohms on the 5 volts rail, i have heard a wire back to one of the low voltage IC's from the 5 volt rail could be a way but not sure beyond that.

    Just wandering if any other member has tried an alternative, my experience is average i would say, so am no expert, and ideas appreciated. :)
     
  2. CraziestOzzy

    CraziestOzzy

    18
    0
    Jul 4, 2012
    G'day...some require a load resistor and some don't. Some have different colour codes for their wires too.
    I have in use a few old ATX's that are running without the need for a resistor to create false load.
    Trial and error with a multimeter will help you in deciding what's betst for the supply you have and what cables to connect for a clean start and run of the unit..
    This site below I link to, I have used ages ago and it's still around.

    http://www.hidplanet.com/forums/sho...wer-Supply-for-10-Computer-Power-Supply-HowTo
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Apparently, newer power supplies may not need this load, or may work without such a large load.

    In this case the resistor IS the trick. it is an alternative to hanging half a motherboard off the power supply...
     
  4. docb

    docb

    131
    2
    Feb 11, 2010
    Yes, just the old ones need this load.
     
  5. sureshot

    sureshot

    234
    13
    Jul 7, 2012
    Thanks for your reply's, so what ive heard on taking a +5 volt wire back to an IC on the low voltage side of the supply is not really needed in terms of newer units, i was just going down the road of a suggestion a friend made on not needing a resistive load but take this so called wire back to a pin on one of the DIL IC's but if its unnecessary i wont keep looking, anyway thanks guys. :)
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,419
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    Jan 21, 2010
    I'm not sure it's ever required.

    If it were that simple for them to operate without a load, they would have been designed that way.

    About the only ICs on the low voltage side tends to be a single optocoupler. On a typical computer PSU, only a single rail is regulated, the rest simply track it.
     
  7. docb

    docb

    131
    2
    Feb 11, 2010
    On the new PSUs there's a line called "Power_ON". Might be pin 13 or 14 - I forget. You short this to ground to tell PSU to turn on.

    Look for docs online. This is common.
     
  8. sureshot

    sureshot

    234
    13
    Jul 7, 2012
    Ok thanks for the ideas i will look it up see what i can find, if not the load resistor is no problem, was just trying to find options to less idle current. :)
     
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