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Blown Brand New PSU

By josopholopodus
Dec 20, 2003
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  1. I am resonably new to this pc building lark.
    Put together a pIII system following motherboard manual to the last word.
    Everything was connected correctly and the time came to switch on the mains.
    One pop and a large spark out of the psu later and i have no power!
    Any ideas what could have caused it and what i should check as i dont want a repeat with my new expensive psu.
  2. Rick

    Rick TechSpot Staff Posts: 6,304   +52 Staff Member

    I don't think you've done anything wrong. This was probably just luck-of-the-draw, or should I say lack there of...?

    It isn't uncomming for cheap or underpowered PSUs to blow out like that. Modern systems require a minimum of 300w or greater, (Or so the majority would have us believe).

    Unfortunately, since higher wattage PSUs are more desirable than ever, there are many cheesy PSUs which sport high wattage & low prices... at the cost of quality of course.
  3. Tarkus

    Tarkus TechSpot Ambassador Posts: 837

    you may also want to check with an ohm meter between 5V, 12V and ground on your MB with the cable disconnected and check for shorts. Also when I used to work in manufacturing I have come across 4 pin molex connectors wired wrong, That usually sends a drive up in smoke though. Another thing is when a PS crowbars it won't power back up until the wall power cord is disconnected for a few seconds. But usually there are no sparks. It should just not power up if there is a short, but with cheap, noname brands anything is possible. Sounds like you probably just did get a bum PS. I use Antec for any computer I build. I like their 380W and 480W units, depending on what load they have to drive.
  4. Shiney

    Shiney TS Enthusiast Posts: 223

    It does sound like the PSU was faulty, but as a precaution I would check your MOBO mounting studs are not shorting anything out.
    When you get a new psu just plug main connector in first and try it, then add 1 connector at a time then restart, follow this procedure until you have everything plugged in.

    I find this is the best way to check for faulty devices, hope it helps you.
  5. josopholopodus

    josopholopodus TS Rookie Topic Starter

    Thanks, put new psu in and works fine... except!
    When i turn off pc the psu fan stays on, and cd drives have power. Power switch coesnt work and it requires turning off at the mains before it will boot again. But when i turn it off this happens again. Its got me stumped? Very strange. also reset switch doesn't work. Could it be a short somewhere?
  6. novicegamer

    novicegamer TS Rookie Posts: 119

    Are all conections from PSU to MOBO connected properly,there should be 2 one big,& one square 4 pin.Also check to make sure you didnt accidently knock off A wire from switch to MOBO usually bottom right of mobo
  7. Shiney

    Shiney TS Enthusiast Posts: 223

    You need to check your case connections to motherboard are in the correct way. Also check your bios settings under power saving.
    Try holding the power switch in for about 4 seconds to see if it turns off.
    When you close windows does a message come up saying your computer is safe to turn off ?
  8. josopholopodus

    josopholopodus TS Rookie Topic Starter

    Ok, think i've sorted it now. Windows was shutting it down fine, it was just the power button that wouldn't turn it off. Looked in the bios again and there was an option to use the power button to send the pc to sleep (so to speak!) rather than shut it down, which, obviously as it previously had no o/s just made the screen die and everything else stay on!
    Yes, i am a muppet!
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