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By on September 5, 2007

atx smps test

ATX SMPS Test is very easy. Just use a scrap motherboard and connect the power supply onto it and place a wire across the two pins shown in the picture below in order to turn the ATX power supply “On”. If possible place two more harddisk to act as load just incase the single motherboard load not enough to switch it on. The symptom could be the fan rotate for a while and then totally stop!

atx power supply on

Be cautious that not all ATX power supply support all kinds of motherboard. Some power supply just need back its own motherboard or system in order to function properly. Hope after reading this tips you should not have any more problem for ATX SMPS Test.



  1. admin

    October 7, 2011 at 2:54 am

    HI Naval,

    No unless if the power supply produce 24 volt. You may use a boost circuit to boost it from 12 volt to 24 volt.


  2. Manish

    October 9, 2011 at 2:44 pm

    dear sir ,
    we have many PC's SMPS power supply faulty of 400W /450 W etc. Will u please help me howand from where i should start , can you give me the Test point of those Power supply so that i can guess on which part fault is there . Hope you will giude me
    My nother question is that we need on;y 12 V Dc output not other volatage , will you please help me to remove the electronic component from that SMPS so that supply will be less bulky and easily we can troubeshoot the fault
    HOPE an egarly waitng for yout reply
    Thanks in advance

  3. Manish

    October 9, 2011 at 3:16 pm

    dear sir
    can you the actual schematic of smps power supply of PC so that we can know easily whcih one is primary circuit and which one is secondary .
    We have power supply in which we are getting PS On votage +5v but we are not getting +12v dc output which component got damaged please help

  4. admin

    October 11, 2011 at 2:40 am

    HI Manish,

    All these i have documented into my ebook smps repair at


  5. Abhishek

    October 11, 2011 at 7:45 am

    hello sir

    i want to get 14 volts from a 300w SMPS for it possible?

  6. admin

    October 11, 2011 at 11:51 am

    HI Abhishek,

    The output is only 12 volt unless if you can find a boost circuit.


  7. duvaraganath

    October 16, 2011 at 5:01 am

    computer cpu smps line and neutral short circuit. with component failure. how to check. details briefly.

  8. duvaraganath

    October 16, 2011 at 5:07 am

    computer cpu smps working but some time restart cpu. small sound in the smps cpu off condition and cpu off condition. power cord insert the smps produce the sound without smps on condition.not sparking and fan sound.

  9. admin

    October 17, 2011 at 4:12 am

    HI Duva,
    Try check all the components in the AC SOCKET AREA particularly on the non polar capacitor, varistor or even bridge rectifier. Chances is high the varistor may have shorted.


  10. admin

    October 18, 2011 at 12:28 pm

    HI Duva,
    Try replace the power supply and retest.


  11. V. Mani

    October 31, 2011 at 7:05 am

    How am I test a transistor is in a good condition or not?

  12. admin

    November 1, 2011 at 12:06 pm

    HI Mani,

    I have compiled it into an ebook


  13. VISHNU

    November 3, 2011 at 4:16 am

    when i turn on my UPS the fan of SMPS and motherboad will be on(WITH OUT SWITCH ON MY CPU) and also some time CD drive will be on.After switch on my CPU computer work properlly.What is the problem?

  14. admin

    November 4, 2011 at 7:56 am

    Hi Vishnu,

    Try power on without the UPS and see what will happen.


  15. peer

    November 29, 2011 at 8:46 am

    my system will not start after shutdown,After 1 hour it will work,but it works with restart.

  16. admin

    November 30, 2011 at 3:03 am

    HI peer,

    It can be caused by the motherboard or the power supply. You need another power supply to confirm it. If you do not have extra power supply, you may need to check if the motherboard or the power supply have any bulged e-caps or not.


  17. Deepak

    December 2, 2011 at 4:45 am

    Hi Jestine, I need one help from you. I have CPU but when i powered on with the mains the computer will not going to start for 15 min to 20min rather i can see the there will be blinking in HDD LED and POWER LED. These LED's will be blinking for 20 min afterwards it will starts normally. After that everything is fine. Can you please help me out in this issue. I need clarification is it problem from SMPS or Motherboard

  18. pinku Dalal

    December 13, 2011 at 2:21 am

    I have a atx smps.When i short green and black wire smps not on,after that i check green wire 5v voltage and violet wire 5v.output filter capacitor are please would tel me how to resole the problem.

  19. admin

    December 13, 2011 at 12:03 pm

    Hi Pinku,

    Did you connect to the original motherboard?


  20. karthi

    December 18, 2011 at 8:45 am

    smps is get voltage but when i shot it not turn on

  21. admin

    December 19, 2011 at 10:03 am

    HI Karthi,

    It can be any component bad that have prevented it to be turned on. Check filter cap and if if the power supply is using a power ic then make sure there is supply to the power ic


  22. Mayur

    December 27, 2011 at 12:19 pm

    pc is buffering what i do i change RAM

  23. admin

    December 27, 2011 at 8:55 pm

    HI Mayur,

    Could you give more details?


  24. ancil

    December 29, 2011 at 2:04 am

    when i try to turn on my pc,the processor fan works for 2sec and then stops and a power led in the mother board is turned but the pc never it the problem of smps?

  25. admin

    December 29, 2011 at 11:25 am

    HI Ancil,

    Hard to tell because either power supply or motherboard problem also could cause such problem. i suggest that you get another pc power supply to confirm it.


  26. Srivatsa

    December 30, 2011 at 8:32 am

    Hello Sir.. 🙂
    I just have a curiosity based question... What will happen if our SMPS fan is manually stopped for prolonged time? I've done the same to check whether the more noise was coming from SMPS fan itself. When i tried to do so.., the noise reduced to almost nothing...
    Plz do reply...
    Thnkx in advance 🙂

  27. admin

    December 30, 2011 at 2:49 pm

    Hi Srivatsa,

    If the fan have stopped this will cause the heat in the power supply to build up. In the long run the components could turn bad and prevent the power supply from functioning.


  28. Dharanesh

    January 13, 2012 at 12:54 pm

    Hello sir.i have 3 fault atx psu. All are not on when i short green and black wires . When main power supply is ok. Please help me

  29. Dharanesh

    January 13, 2012 at 1:00 pm

    Hello sir. One of my atx psu fuse always damage when power on smps without connect any harddisc and mother board. Please help me

  30. admin

    January 13, 2012 at 8:56 pm

    HI Dharanesh,

    May in know what are the components you have checked?


  31. admin

    January 13, 2012 at 8:57 pm

    HI Dharanesh,

    If the fuse always blow please check the bridge rectifier, power transistor and also varistor.


  32. Dpunkr

    January 17, 2012 at 1:58 pm

    I want to use a extra smps to run two extra 120 mm chassis fan,5 LEDs in my cabinet is it possible

  33. admin

    January 19, 2012 at 7:26 am

    HI Dpunkr,

    Yes you can and make sure those fans are computer fans.


  34. Raushan raj

    January 27, 2012 at 12:27 am

    Sir my system say that +3.3v fail what shall i do please haelp if i change my smps then what or hang my system

  35. admin

    January 29, 2012 at 4:56 pm

    HI Raushan,

    If the 3.3 volt line have problem and you wish to change the power supply then just buy a new one and fix it and retest. it should work fine with new power supply.


  36. Ranjan singh

    February 19, 2012 at 1:31 am

    Sir I want a circuit diagram of smps and ups for persional computer use.
    so please send me a circuit diagrams of smps and ups for computer.

    Your sincerely

  37. admin

    February 20, 2012 at 9:33 am

    Hi Rajan,

    Sorry i do not keep schematic. Try


  38. nk

    February 25, 2012 at 5:35 am

    I m having with a computer(PC).after few checking I found the problem is in the motherboard or may the CPU..if it is in motherboard how could I find which components causing this.....Details of the problem computer won't boot.....

  39. admin

    February 25, 2012 at 11:40 am

    Hi NK,

    Can't boot problem can be easily checked by using a pc post card:

    Without the pc post card it is hard to determine which section is faulty.


  40. victor

    March 3, 2012 at 2:54 pm

    There was a surge / power fluctuation at home and my computer stopped working.
    I came home and ignorant of the same, i powered the computer and UPS fuse blew off.
    Now i removed the SMPS shorted the green and black wire and found that SMPS fan is not working.
    Could it have damaged the mother board and other components?
    kindly let me know what could be problem and solution in future for a sturdy SMPS 600W or more which can run for weeks without shutdown.

    • Jestine Yong

      March 4, 2012 at 1:17 am

      Hi Victor,

      It can be the power supply and the motherboard problem since it was hit by a surge. I suggest that you get a good unit of power supply to compare and see which one is causing the problem. If you have electronics repair knowledge then you can check on the power supply fuse and etc.


  41. Almas

    March 4, 2012 at 2:04 pm

    How can I repair or pinout of compaq power supply 332112

  42. kannan chellaiah

    March 24, 2012 at 3:13 am

    hi Iam kannan from india . my system cpu added two hdd and one dvd . so some time not working one hdd pls help me.

  43. Ankit

    April 7, 2012 at 12:54 pm

    when i try to turn on my pc,the processor fan works for 2sec and then stops and my pc never starts.
    Sir i have tested my motherboard with other smps it is working...
    So please tell me how to repair my smps ?

    • Jestine Yong

      April 8, 2012 at 3:29 am

      HI Ankit,

      You need to check if the power supply e-caps are good or not. You need to test it using ESR meter.


  44. Rajesh

    April 9, 2012 at 1:23 pm

    Dear Jestine,
    Yesterday, When I switched on the main supply of my computer, suddenly I saw like a flash light form ATX's SMPS side and on same time MCB of main supply was trigged. From that time my computer is not starting. Triggering of MCB indicates that there is some short circuits in SMPS.
    So I opened SMPS but I did not found any burned electronic components and everything is looking fine inside SMPS.
    So what problem may be possible with SMPS?
    I have Intex ATX P4 Power Supply JIL-2410 (with 20+4 pins) SMPS.
    Please reply,

    • Jestine Yong

      April 11, 2012 at 12:29 am

      HI RAJESH,

      IT could be the varistor have shorted from the live/neutral line to ground. Or juct check all the components in the ac supply input area. It could be non polar square cap shorted too.


  45. Ankit Aggarwal

    April 10, 2012 at 12:32 pm

    Sir , i don't have ESR meter , so please tell me some another way

    • Jestine Yong

      April 10, 2012 at 9:36 pm

      Hi Ankit,

      Try direct replace and retest since you co not have the esr meter.


  46. Ankit

    April 13, 2012 at 2:04 pm

    Thankyou Sir

  47. safa

    May 8, 2012 at 2:52 pm

    what is the input voltag range of  ATX  600w power supply....

    • Jestine Yong

      May 9, 2012 at 4:42 am

      Hi Safa,

      if the power supply is the auto range then it can take in 100v to 240 vac.


  48. Ronelex

    June 25, 2012 at 3:59 am

    nice article, very informative,
    The symptom could be the fan rotate for a while and then totally stop! 
    The problem in this situation maybe transistor look alike diodes that is shorted which is the source of the 12v output of the supply, am I correct?

  49. Wimpie

    July 6, 2012 at 7:32 pm

    Hi Jestine
    how to test varistor is the varistor looking like non polarised capacitor im a beginner
    Thanx Wimpie

    • Jestine Yong

      July 6, 2012 at 8:11 pm

      Hi Wimpie,

      Just set your analog meter to x 10 k ohm and it should have no readings on both way of checking.


  50. Wimpie

    July 12, 2012 at 8:23 am

    Hi Jestine'
    Thanx for the advice. Im busy with my first repairing project wich is the atx computer power supply and the fuse blew right out of the board. I also found dual schottky rectifier sbl 2040ct short on both pins in the secondary side of smps. The bridge rectifier also dead short on two diodes. My problem is i cant find the schottky rectifier sbl 2040ct. Do u know what i can do or use as a replacement and to import the part is gonna cost me more than the whole power supply.Thanx a lot for all the good advice.

    • Jestine Yong

      July 12, 2012 at 9:16 pm

      Hi Wimpie,

      Try this link:



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