power supply problem

By crobarred
Oct 8, 2003
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  1. After troubleshooting my previous issue I finally got my computer up and running. However after I put in my various PCI cards into the motherboard when I started up the computer....it turned on then off. I tried to restart it but when I would cycle the power it wouldn't turn on. I would have to unplug it, plug it back in and then I would get the same result: the fan would spin then it would power down. The power supply is new. I have tried everything from taking all PCI cards and removable drives off the power supply to resetting the CMOS in case I messed up a setting in there. Any suggestions?

    Crobarred
  2. Nic

    Nic TechSpot Paladin Posts: 1,928

    Please post the make/model of your PSU. Looking at your system specs, I would expect that your PSU is not powerful enough to supply the demands of your system. Once you provide more details it will be easier to narrow down your exact issue.
  3. crobarred

    crobarred Newcomer, in training Topic Starter

    The PSU in question is a Comp USA brand model that is 450watts. I have a three hundred watt model that seems to sustain the necessary voltage to the board. However I would like to put the 450W back in so I can put in another HD or two. The PSU is pretty new so I dont' think it burned out..plus I don't smell any burned components/resistors and the like...

    Crobarred
  4. Nic

    Nic TechSpot Paladin Posts: 1,928

  5. StormBringer

    StormBringer Newcomer, in training Posts: 2,871

    Voltage and current not the same thing. The +12v rail for example is putting out +/-10% of +12V DC, but the load you put on that rail is going to draw current(amps) This is the major problem most people seem to run into. They buy a PSU that supplies too little current for the demand. The overall power rating(Watts) does not tell the true tale, which is that each rail can only supply a certain amount of current effectively. The Entire PSU also only supplies a given amount of current. These ratings add into the overall rating.

    In the thread Nic referenced, there is a link to a chart somewhere that explains this in pretty simple terms.

    To put it simple, if you have less than 17A on the +12v rail, you need a better PSU. I believe that most people are now recommending 20A+ if using the latest CPUs and high end vid cards.
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