New PSU, but p.c won't boot.

Discussion in 'Power Supplies and UPS's' started by Matac, Oct 25, 2007.

  1. Matac

    Matac Geek Trainee

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    A friend of mine asked me to look at their p.c to me becasue it no longer worked, it wouln't start up. So i opened it up, putlled all the 'extras' (HD CD drive etc.) power leads out and tried it.
    The PSU hummed for a few seconds the CPU fan spun. But then it died again. So i assumed it was the PSU (I was round their house and no other p.cs to test it on) and found him one to buy. When it arrived i swapped them, and plugged in the two motherboard sockets which problem No.1 came up.

    The PSU has a 24 pin connector, but the motherboard as a 20 pin connection. On the actually connector there was a little divider on the last 4 pins so i assumed this was the 'extra' 4 pins that some motherboards need. Is this the problem, and do i need to find a 20pin PSU or is just that my mates p.c is old and that new p.c use 24pin to get more juice?

    Anyway after, plugging in the 2 connectors and connecting up the powercable the PSU and CPU fans started spinning and the power light on the front had lit up, even tho i hadn't even touched the power button yet. I tried pressing the power button anyway and nothing happened, the p.c did not start to boot. I tried turning it of by pressing and holding the power button and it did not turn off.

    I checked the cabling from the power switch to the motherboard (red, green and black ones) and they seemed fine, up until the point my friend pulled them out. Which is problem No. 3 I can't remember the order they go in, is it standard or is different for each motherboard?

    But even with the power switch cables pulled out, i plugged the power cable back in and again the PSU and CPU fans start spinning.

    Now if anyone even read this far, and can still makes sense of what i've written (I know I waffle abit) can anyone help with my problems?

    Matt
     
  2. Big B

    Big B HWF Godfather

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    What's the specs of this system and what power supply are you using?

    Off the top of my head, it sounds like either there's a problem with the CPU cooling or the power supply isn't up to snuff.
     
  3. Matac

    Matac Geek Trainee

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    Yeah after typing out that huge message i realised that i hadn't actually put any of the specs in :dry:.

    The PSU is a 1 x Sumvision 350W PSU 20+4pin SATA.
    The Motherboard is unmarked (or atleast i can't find any names) I've tried botting with nothing extra plugged in, only Motherboard and RAM.

    The problem that is the strangest is when plugging in the power cable the PSU and CPU fans both spin, without any promting or action on my half.

    I will continue to research the motherboard type and shift throught the reems of paper work my friend recieved with his p.c (its really old).

    Thanks
     

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