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Thread: Power problems - unstable rails

  1. #1
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    Power problems - unstable rails

    Hi, I have just built a new PC and it seems to be running reliably, but the 5V, -5V and -12V rails are being reported as fluctuating wildly in Sisoft sandra and PC Wizard 2006.

    The +/-5V rails are reporting as fluctuating from 2V through to 6V, and the -12V seems to fluctuate from -4V to -12V.

    Prime 95 torture test ran stably for 2 hours, and everything seems to work reliably. What is going on?

    Socket 939 Athlon 64 3200+
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    2GB corsair value select ram
    Geforce 6800 GS PCI-E graphics
    Pioneer DVD RW
    DVD ROM
    Hitachi deskstar 250GB HD
    120 GB IDE HD
    40 GB IDE HD
    Seasonic 500w power supply

    Tigger

  2. #2
    YUKIKAZE arthurleung's Avatar
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    • arthurleung's system
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    -5 and -12V rail doesn't matter. If your +5V rail really fluctuating badly thats what you need to worry about.

    Your Seasonic should push the above with ease
    Workstation 1: Intel i7 950 @ 3.8Ghz / X58 / 12GB DDR3-1600 / HD4870 512MB / Antec P180
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  3. #3
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    • aidanjt's system
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    Quote Originally Posted by Tigger
    Hi, I have just built a new PC and it seems to be running reliably, but the 5V, -5V and -12V rails are being reported as fluctuating wildly in Sisoft sandra and PC Wizard 2006.

    The +/-5V rails are reporting as fluctuating from 2V through to 6V, and the -12V seems to fluctuate from -4V to -12V.

    Prime 95 torture test ran stably for 2 hours, and everything seems to work reliably. What is going on?
    Faulty voltage sensors, use a real multimeter to test your rails.. that kind of wild voltage fluxuation would destabalised your computer.
    Quote Originally Posted by Agent View Post
    ...every time Creative bring out a new card range their advertising makes it sound like they have discovered a way to insert a thousand Chuck Norris super dwarfs in your ears...

  4. #4
    Treasure Hunter extraordinaire herulach's Avatar
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    Its possible that your power supply doesnt actually have a -12V rail, hence why the readings are waky

  5. #5
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    Thanks for the info, I wouldn't know where to start to find the different rails with a voltmeter and to be honest I don't fancy blowing the motherboard by randomly stabbing voltmeter probes on to components. I have an old generic 400W PSU which I was going to try to see if the same results occur.

    Can anyone suggest other software to monitor the voltages in case the conversion factors in Sisoft sandra and PC Wizzard are incorrect? How can I tell what system health chip I have and what it is capable of measuring? I have the gigabyte easytune 5 software which came with the motherboard, and the system health part of that program only monitors Vcore, +3.3, and +12 which are all rock solid. Wouldn't they have included the other voltages (+5, -5, -12 and standby) if the chip could monitor them, as these are the ones which other software reports as fluctuating?

    Tigger

    Socket 939 Athlon 64 3200+
    Gigabyte GA-K8N Ultra 9
    2GB corsair value select ram
    Geforce 6800 GS PCI-E graphics
    Pioneer DVD RW
    DVD ROM
    Hitachi deskstar 250GB HD
    120 GB IDE HD
    40 GB IDE HD
    Seasonic 500w power supply

  6. #6
    Treasure Hunter extraordinaire herulach's Avatar
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    • herulach's system
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      • Memory:
      • 8GB Vengeance LP
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    Dont worry about -5 and -12, they arent used, as i said, your psu prob doesnt have them.

    To test the 5V rail you can just put a multimeter across the red and black connectors on any molex.

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