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Intel cooling fan shuts down power supply

Discussion in 'Intel' started by George Orwell, Sep 11, 2010.

  1. A friend gave me a PC what did not work. It has Pentium
    socket 478 and Intel cooler. When switched on, it shuts
    down after 1 or 2 seconds. I started removing things, and
    it was down to motherboard still stopping it. I put an ATX
    power supply tester on instead, and the power supply stays
    on. But this is no load. Out of curiosity, I connected the
    CPU fan to the power supply and bingo - it stopped. I had
    a few spare Intel fans and connected those instead. The
    power supply stays on. So I measured the resistance across
    the black and yellow wires of the killer fan and it reads
    open circuit (well greater than 2 megohm). All the good
    fans read 1800 to 2000 ohms with same meter.
    Weird eh? A high resistance drags down PS!!!

    Il mittente di questo messaggio|The sender address of this
    non corrisponde ad un utente |message is not related to a real
    reale ma all'indirizzo fittizio|person but to a fake address of an
    di un sistema anonimizzatore |anonymous system
    Per maggiori informazioni |For more info
    https://www.mixmaster.it
     
    George Orwell, Sep 11, 2010
    #1
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  2. George Orwell

    TVeblen Guest


    http://en.wikipedia.org/wiki/Short_circuit
     
    TVeblen, Sep 11, 2010
    #2
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  3. No, a switching power supply controls voltage by limiting the "on time" power is
    sent to the filter system to become (more or less) DC. As load falls (high
    resistance) eventually the switching time becomes too small, the output waveform
    changes from a ripply DC to flat with spikes, and it shuts down before the
    crappy DC breaks something. Connect any load, and the DC gets better.

    NOTE: the symptoms sound like a short rather than an open, but many power
    supplies will not work feeding just a motherboard, it doesn't draw enough load
    at some voltages. A moderately good explanation is at:
    http://en.wikipedia.org/wiki/Switching_power_supply#Explanation
    Again, I am taking your high resistance measurement at face value, even though
    you would expect the system to start, then the CPU to shut down with no cooling.
     
    Bill Davidsen, Sep 19, 2010
    #3
  4. George Orwell

    alexmax021

    Joined:
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    Great post! It's very nice. Thank you so much for your post.
     
    alexmax021, Nov 25, 2010
    #4
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