300 watt computer smps problem

Discussion in 'General Electronics Chat' started by Peter_England, Jun 29, 2013.

  1. Peter_England

    Thread Starter Member

    Jun 29, 2013
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    Hi, I am facing problem with smps.. It's getting auto shutdown self after starting for 5 to 10 minutes I have checked it using smps tester all outputs are looking fine. Pls help in this case.
     
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    On your psu there is a Green wire that is the start/stop feed from the computer, it goes low for on and high for off, what is happening to that feed, see if it keeps going high. Also when the psu is up and running it gives out a +5V on the Grey wire to tell the PC to start up, it may be shutting down due to over-current sensing.
     
    Last edited: Jun 29, 2013
  3. Peter_England

    Thread Starter Member

    Jun 29, 2013
    73
    1
    Thanks. Grey wire is giving 4 volts. I am using to test the smps tester.
     
  4. Peter_England

    Thread Starter Member

    Jun 29, 2013
    73
    1
    Green wire is go low when starting psu
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    I had a CPU heatsink problem such that the chip would overheat, sense the danger and SHUT THE WHOLE COMPUTER OFF.

    No warning, no blue screen. Power on one second, off the nest.

    I didn't suspect this until the next power supply did the same thing.

    Moral: it may not be the power supply. It may be the computer.
     
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  6. Peter_England

    Thread Starter Member

    Jun 29, 2013
    73
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    No but in this case this is not true it happens without motherboard also. Thanks.
     
  7. Peter_England

    Thread Starter Member

    Jun 29, 2013
    73
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    Hi Erniem pls help me solving this.
     
  8. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    if its going into shutdown on its own then its either over volts or overcurrent.
     
  9. Peter_England

    Thread Starter Member

    Jun 29, 2013
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    Thanks dodgydave I will check that way.
     
  10. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    if you want to repair it then open it up and see what chips are inside, but trust me its far cheaper and simpler to just buy a new one.
     
  11. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The epoxy binder in inductor cores tends to age and iron powder (or ferrite) moves slightly, then inductance goes down and bad things start to happen with the control circuitry.

    Easiest to replace the power supply for 20 or 30 USD.

    Note: paying more for a brand-name power supply will, in most cases, get you better inductor cores and bigger heat sinks. Apple power supplies used on their desktops are really high-end and last forever (alway exceptions - but rare).
     
  12. Peter_England

    Thread Starter Member

    Jun 29, 2013
    73
    1
    Actually I am working as support person in IT department of non-profit organization and directed to keep budget as much as low.
     
  13. Peter_England

    Thread Starter Member

    Jun 29, 2013
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    And we have about 400 DESKTOP COMPUTERS so I think this is the good way to first try for repair things and if it not repairable then go for new one.
     
  14. Peter_England

    Thread Starter Member

    Jun 29, 2013
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    I agree with Mr.gopherT but what wrong in trying first. And if the problem is just a blown resistor or I mean. Not big problem then I must go for it.
     
  15. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    Well open it up and tell us what ic's are inside, it may be an over volts/current sense pin
     
  16. ian field

    Distinguished Member

    Oct 27, 2012
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    Most PC PSU will not operate without an in-spec load.
     
  17. ian field

    Distinguished Member

    Oct 27, 2012
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    If you're going to open it up, its as well to inspect the tops of all the electrolytic capacitors. Bulged tops and splitting is a sure sign of overheating, but the tops can also develop a slightly sunken appearance - this indicates that heat has forced out some of the electrolyte leaving partial vacuum when it cools.

    I'd suggest feeling for hot electrolytics while the PSU is running - but some on the primary side have high voltage on the aluminium can!!!

    Obviously while the PSU is open - make sure the fan is working and airflow not obstructed.
     
  18. Peter_England

    Thread Starter Member

    Jun 29, 2013
    73
    1
    The model is DELTA GPS 300 AP. This SMPS has two ic one is 16 pin DWA105 N161 907 J03A3
    and. Another is 8 pin UC3843BN. CPCG 0904G..

    And it has no bulged caps. I am attaching image.
     
  19. Peter_England

    Thread Starter Member

    Jun 29, 2013
    73
    1
    Sorry but how to attach a file directly without web link? Thanks.
     
  20. bertus

    Administrator

    Apr 5, 2008
    15,649
    2,348
    Hello,

    This page on SMPS repair might interest you:
    http://www.repairfaq.org/sam/smpsfaq.htm

    It is made for small SMPS powersupplies, but I think a lot will apply to the computer powersupply.

    Bertus
     
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