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Power supply/case short issue?

By Tollas
Sep 23, 2006
  1. I'm assembling a new system and having power issues. When connected and the switch on the power supply is on, all my components receive power before I press the power switch. Fans turn, DVD drive spins and opens, yet I am not able to power up my computer. I stripped everything down to just the motherboard, CPU and RAM and I still get nothing. No POST beep or anything signaling a startup taking place.

    I am wondering if this could be caused by a faulty power supply (ie a short inside the power supply) or more likely by a short in the case somewhere. Any help in resolving this would be appreciated!
     
  2. N3051M

    N3051M TS Rookie Posts: 2,800

    reassemble the minimum system components outside of the PC case on a non-conductive surface (eg the box that came with your motherboard). this will show you if its shorting to the case or an isolated problem.

    What brand and model is the PSU?
    Reseat all the components (ram, video card, etc).. you might want to try reset the BIOS at this stage since you've got nothing else to do :)

    It is normal for some PSUs to start up the fans and/or other devices for a few seconds after puting in power to it or after shutting down the PC, but irregular if it doesn't die down by itself after a few seconds to a minute or if you can't manualy trigger it (shorting the two pins instead of pressing the power button to turn on the PC)
     
  3. Tollas

    Tollas TS Rookie Topic Starter

    power supply is a xion LC-B450E (came with the case)

    I assembled outside of the case as instructed with the same results. CPU fan spins up but no attempt at a POST when power was jumpered.

    Got a new PS (RAIDMAX) and I'm getting the same results. Means it's a motherboard issue after all.
     
  4. N3051M

    N3051M TS Rookie Posts: 2,800

    i'm probably banking on the same thinking.. RMA it or get it exchanged and test..
     
  5. Tollas

    Tollas TS Rookie Topic Starter

    Exchanged it and everything works great. System is up and 100% now. Thanks!
     
  6. N3051M

    N3051M TS Rookie Posts: 2,800

    Thats cool :)
    Have fun!
    N3051M
     
  7. chessonly

    chessonly TS Rookie Posts: 65

    I am getting a similar behaviour.
    The moment I switch on the power to the cpu the fans (both psu and cpu) run for second and then switch off. Then when the power button is pressed there is no response.
    If the psu is not connected to the cpu then the fans do not run atall. Does this indicate that the PSU is dead or is there any other possibility?
    Thanks
    Specs : PIII , 350w tech-com ATX PSU , some Intel mobo. 128 or 256mb ram ( its a friends cpu)
    Edit2: and the psu is very light ( weight wise) even lighter than my 200w PIII AT power supply which hasw been running for 9 years now :D
     
  8. Tmagic650

    Tmagic650 TS Ambassador Posts: 20,915   +167

    "It is normal for some PSUs to start up the fans and/or other devices for a few seconds after puting in power to it or after shutting down the PC, but irregular if it doesn't die down by itself after a few seconds to a minute or if you can't manualy trigger it (shorting the two pins instead of pressing the power button to turn on the PC)"

    I woundn't say this is really "normal"... if the fans start with just plugging in the power supply, this means that a previous attempt to start was interrupted or had failed. The motherboards bios may get a little confused with the power settings (stay on, stay off etc)

    chessonly,
    replace the power supply. It may be the motherboard, but the power supply is easier and cheaper to start with
     
  9. N3051M

    N3051M TS Rookie Posts: 2,800

    Clarification: When you first plug in the PSU to the wall and turn it on using the switch at the back of the PSU the fans will spin up for a second. This is before you press the power button for the PC. Also when you go shutdown and your whole PC is turned off, the PSU fans (and any other fan thats connected to the fan lines of the PSU) will keep running for a minute or so as a cool down phase type of thing..

    Chessonly: i agree with Tmagic to replace the PSU first, as 9 years is a good run for any PSU and may as well have passed on..
     
  10. Tmagic650

    Tmagic650 TS Ambassador Posts: 20,915   +167

    N3051M,
    I don't repair or build many hi-end systems here, but I have 4 systems in this office right now and they don't exhibit this momentary spinning of the fans. Once they are shut down, I can pull the AC plug and re plug it in. I can turn the power supply switch off and on with no fan spin. If I pull the plug on a system without shutting it down, the fans will spin momentairly when I plug in the power supply. Also, the fans won't keep spinning when the system shuts down. The fans stop as soon as thieir momentum fades away... Just a matter of seconds
     
  11. N3051M

    N3051M TS Rookie Posts: 2,800

    like i said, different models of PSUs does different things. hence why i've included the word "Some".

    normal/common PSUs would probably be like what you've seen (off = off), and yes i know since i have 2 other PSUs in the house that does that so you are correct at your observation.

    when my PC died a few of months ago i decided to replace the PSU with a Coolermaster 400W and it exibits this behaviour, which is normal since some of my other friends who've changed to different brands/PSUs especialy with seperate fan lines as part of the supply cables from the PSU. How i know this is that the LEDs from the fans stay on for around a minute before switching off, so its not residual momentum.
     
     
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