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Ongoing 'turning off' issues... need help!

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    Ongoing 'turning off' issues... need help!

    Hi Guys & Girls,

    Been a while since I have posted... been a bit busy recapping things! The problem I need help on in a qwerk that my Dad's PC has developed. It was built up to its current form about 4 months ago with the following parts:

    Aopen case
    Antec Smartpower 500w PSU (all caps replaced with saxmon/rubycon)
    DFI Lanpart NF4 UT Ultra-D 939 motherboard (new)
    AMD Opteron 180 (X2 64)
    4 x 512mb ram
    Nvidia 8800GTS PCI-E card
    Seagate 7200.10 320gb Sata drive
    + 2 dvd drives etc)

    And has been running like a good-un up until a 3 weeks ago when it would randomly turn off with no warning or errors (just like a power cut). It has proceeded to get worse where it often doesn't like to be turned on now as well!

    I figured I had a bad cap out of the ones I replaced in the Antec that didn't last very long... but upon stripping out the PSU and checking all the caps with an ESR meter they all tested fine! Plus when I tested the outputs of the PSU they were all within spec of when I recapped it.

    The Caps on the M/B are all either Chemicon KGZ (known to go bad I know) or poly's.., but after only a couple of months I wouldn't think they are at fault.

    So the next thing I thought of was that it was getting too hot, which was causing the shutdown (even though its winter here). So I added a second case fan at the back and put the flow direction to suck and created some vents in the fron of the case to act as a wind tunnel. I then set all the fans to 'ultra loud' when the system reaches only 35 degrees in the bios... rather than the quiet volume they had been happy with before.

    This setup seemed to help the shutdowns... until today when with the fans roaring and the computer being at idle it shutdown once more - and now refuses to start up! I have reset the bios, tested the case switch (no problem) unplugged and replugged all the cables on the M/B and even put a fresh paper thin layer of AS5 on the CPU after scrubbing off the last set. Still no go!

    Out of desperation I unplugged all the PSU cables from the M/B (barring a 4 pin molex 'booster') and then jumpstarted the PSU (green & black) and the motherboard and fans roared to life! So I disconnected the last molex to the M/B and tested the PSU voltages again and they were all go still.

    But after I plugged the 24 connector back onto the M/B (and the other PSU connectors) it has gone silent once more with no lights. Its almost as if the M/B is unable to sustain the 'turn on PSU' signal.

    So Thats the run down so far... I am looking for any hints or advise on things that I should have tried but haven't. I am trying to track down another 24pin psu (I have 4 other 20 pins sitting around though)... but other than that I am unsure how else to determine if it is really the M/B that is at fault.

    Has anyone come accross this kind of thing before? It is a brilliant system when running - but these recent bugs are sending me insane!!

    Cheers Harvey
    Are we there yet? I'm hungry....

    #2
    Re: Ongoing 'turning off' issues... need help!

    backprobe +5stby while you try to start the system.see if it drops when you hit the power button.
    btw i have tested boards with 24 pin psu sockets by using a 20 pin supply.
    it is keyed such you cannot put it in wrong.some cheap emachines systems come that way.
    the antec is suspect #1
    sub it to test.

    Comment


      #3
      Re: Ongoing 'turning off' issues... need help!

      I would do what kc8adu said and test the +5V SB. Better yet, try another PSU to isolate the PSU from the equation so that it makes it easier to determine whats going on. Sounds like the Antec is being a pain even though you've recapped it.... just a quick thought, but maybe there are broken solder joints in the PSU to cause this issue?
      Don't find love, let love find you. That's why its called falling in love, because you don't force yourself to fall, you just fall. - Anonymous

      Comment


        #4
        Re: Ongoing 'turning off' issues... need help!

        Hi kc8adu and Stevo1210 Thanks for the replies!

        I keep a spare 24pin PSU at one of the offices that I work at (We seem to cycle antecs for some reason!) so I grabbed that last night... and bugger me if the system didn't fire right up! So the PSU was to blame!

        I stripped the faulty PSU down on the bench last night for a more thorough going over, esr meter on all caps, testing the fuses (quick blow & thermal both OK), used a magnifying glass to check on my solder joints and looked for any sign of crispy components... yet still nothing!

        This one is a bit of a head scratcher! I shall reassemble it and back probe the +5sty as you suggest kc8adu to see where that takes me... but what else should I be checking as the voltages are all within spec with jumpstarted?

        I have already decided that the Antec is going to be replaced with a Cosair or similar... but I am determined to not let this Antec beat me!

        Thanks again

        Cheers Harvey
        Are we there yet? I'm hungry....

        Comment


          #5
          Re: Ongoing 'turning off' issues... need help!

          I've seen this a number of times with broken CPU heatsink retainers. Insufficient contact of the process and HSF causes a shutdown.
          i have seen that too but in this case it was a bum psu.
          Last edited by kc8adu; 08-25-2008, 03:28 PM.

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