Don't Miss

Fixing a branded ATX power-supply of a PC for 0.50USDs

By on January 20, 2015
atx power supply repairing










Even though the following article is about repairing a branded ATX power-supply of a PC, the scenario I discuses here might be a common issue for most of switching mode power supplies.

atx power supply repair

While I was working with my desktop PC, it went off giving an electric sparking sound like “Chitiz”. Guessing it might be a PS issue, the PS was removed from the PC-casing.

Then having supplied 230V AC power, the output voltage between green and black wire of the ATX connector of the PS was checked. If a PS is in good condition, the voltage between green and black must be 5V.

atx power supply repairing

However as it is in the above picture, the voltage between Green and Black was 1.6V. So it’s pretty clear that the PS was faulty. Then I removed the metal cover of the PS and checked for any burnt components such as burnt resistors, E-bulged caps ….but I couldn’t find any clue at once .

For making further testing easy, I removed one of the heat sinks and checked the following primary side component of the SMPS:

  1. H/V of two main filter caps are correct


However I found no voltage at primary side of the Chopper transformer!! So, most probably the issue should be at the primary side of the SMPS. Then I check directly connected components to the Chopper and found one Fusible Resistor (1 Ohm, 1/2W) got open ! Then, suspecting, one IC (TNY268P Switcher ) which was directly connected with the opened resister, was removed from the PCB and checked. I saw most of pins of the IC got shorted. Having deeply checked it was confirmed the surrounding components were good. 

*** you can find the above two burnt components under the heat sinks!


Then I replaced the Fusible Resistor and the IC – TNY268P with new parts. In Sri Lanka, I spent only 0.5 USDs for above 2 components. Having replaced I checked the voltage between green and black wires again — Now I found 5V  (4.947v) there !!! My PC is working perfectly now!!! 



This article was prepared for you by Kushan Rnatunga who works as a Network Engineer in Sri Langka. He has been doing  electronic experiments since age 11.

Please give a support by clicking  on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.

P.S- Do you know of any your friends who would benefit from this content that you are reading now? If so, forward this website to your friends or you can invite your friends to subscribe to my newsletter for free in this Link.




  1. Anwar Shiekh

    January 20, 2015 at 10:02 pm

    Reminds me of the engineering joke

    $99 for finding which part to change, 1c for the part.

  2. Yiannis

    January 20, 2015 at 10:11 pm

    Very useful and easy , how to repair a faulty ATX power supply with pictures

  3. Robert Calk

    January 20, 2015 at 11:42 pm

    Nice job and good work Kushan. Thanks for the article. The IC is about $1.70 here in the USA.

  4. Yogesh Panchal

    January 21, 2015 at 12:24 am

    good attempt!! congratulation.

  5. Humberto

    January 21, 2015 at 12:31 am

    Good repair Mr. Kushan Rnatunga, congratulations.

  6. gcharal

    January 21, 2015 at 1:07 am

    thank you for sharing this with us.
    I have a question.
    What voltage did you expect to see at Chopper transformer?

    By the way, "Yannis" where do you come from?
    I'm George from Greece!

    • Kushan

      January 21, 2015 at 1:12 pm

      Hi Gcharal

      Thanks for the comments! Actually without the design information I can’t say what should be the correct voltage at the primary side of the Chopper (between primary pins and the Hot-ground/ + of main filter cap ). However generally there should be DC 80V-300V, I suppose. But it can easily be vary from one brand to another.
      When I checked the voltage, some of pins got “0”V , it was abnormal.

      • Amir Mukhtar

        January 21, 2015 at 2:41 pm

        Thank you Mr. Kushan Rnatunga to Share informative Solutions.

        thank you

  7. Tito

    January 21, 2015 at 1:10 am

    Good article's an eye opener especially on the 5V between black and green

  8. Graeme Partridge

    January 21, 2015 at 1:25 am

    There is no mention of a load on the 5v supply? I seem to recall when I used to perform repairs (many years ago now) you needed to load the 5V rail for the PSU to fire up.

  9. Andre Gopee

    January 21, 2015 at 2:07 am

    Great Job.

  10. Merlin Marquardt

    January 21, 2015 at 2:35 am

    Very good.

  11. Mark

    January 21, 2015 at 4:13 am

    Hey Kushan,
    Thanks for the article. I have a ATX that has been sitting on my 'to do' pile for some time now and I should really spend some time working on it. Your article will give me a direction for my diagnostics.

  12. G

    January 21, 2015 at 9:55 am

    Thank you for sharing useful and good experience to all of us.

  13. Kushan

    January 21, 2015 at 1:18 pm

    Thanks Friendzzz!!! your comments encourage me :- )hope to hear yours experiences and findings too

  14. Amir Mukhtar

    January 21, 2015 at 2:44 pm

    The Artice is too knowledgable and Informative for every one due to equipment get back to life again.
    Thanks you Mr. Kushan Rnatunga. Keep Sharing Experiences with Sir Jestine yong.
    Credit Also goes to Sir Jestine for Provide Plat form to every one.

    thanks you Both of you
    A student of Electronics
    Amir Mukhtar Ashrafi

  15. moshe

    January 21, 2015 at 4:09 pm

    great article...thanks for sharing!!

  16. darel

    January 21, 2015 at 6:42 pm

    Very nice article, Anybody here hav eschematic diagram for
    P4 450W AMAX ATX

  17. Anthony Jazdziejewski

    January 21, 2015 at 9:54 pm

    Very interesting Article! I do have some ideas for other electronics. I like this very much! i learn something from every repair article that i read! Thank you very much!

  18. Ehsan Murad

    January 22, 2015 at 11:22 am

    Great Stuff.Well explained.

  19. peter

    January 22, 2015 at 2:18 pm

    Good clear article.
    Please always consider your repairs may be viewed in countries where tech labour costs are relatively high.
    So it would help if you shared the total time this repair took.
    I think I can buy a new PS replacement for around US$20 worth about 10 mins of labour cost.
    Again Thanks

    • Jestine Yong

      January 22, 2015 at 2:37 pm

      Hi Peter,

      Yes many will replace power supplies and even TVs or Monitors but troubleshooting to locate the fault is another thing because some repair techs/hobbyists would like to find out what causes the device to go bad. It is not a matter of buying a new one and replace it but more on the experience gained during the repairing process and the satisfaction be able to repair the device. To some of them earning is secondary, experience/knowledge and sharing come first.



      • Paris Azis

        February 8, 2015 at 1:28 am

        Hi Jestine

        Your descriptive comment reveals the second view of the single reality...The first is "counting dollars" and the second is "counting stars" as the well known song says. Romantic? Perhaps. Nenertheless let's consider what happens at the dump yards of the garbage electronics...On the other hand recycling is still a
        dream for many countries, while the garbage continues to pile up.
        At least electronics' repairers are an obstacle to this process with their contribution, creating a compromising balance between the two views...
        As regards to the time parameter versus repair procedure, in my humble opinion based upon almost 40 years of my involvement in this task, depends completely on the existence and application of logical methodology. There is no substitute or shortcut to this. Either it exists and saves time and headache or it lacks and the repairing work loops again and again in wrong tasks extending the time like a faulty computer S/W does...

        My best Regards

        • Jestine Yong

          February 8, 2015 at 4:25 pm

          HI Pariz,

          A big like for your comment!


  20. tana

    January 22, 2015 at 10:31 pm

    I am learning from you. Thanks for showing the way to trouble shoot .Warm regards . From tana

  21. mahmoud

    January 23, 2015 at 5:00 pm

    thank you kushan it was very useful for me I hope u are sucsesful.

  22. Philip P George

    January 23, 2015 at 10:30 pm

    I am learning a lot from you.thank you very much.

  23. Florin

    January 25, 2015 at 3:36 am

    Can somebody tell me what digital multimeter is Mr. Kushan Rnatunga using in his photos?


    • Kushan

      February 2, 2015 at 11:50 pm

      It's a "Sanwa PC-510a DMM". I'm a very good fan of Sanwa (Japanese) since my childhood. I got my 1st Sanwa MM (YX361TR) @ 11 from my mom. it's still working perfectly. Sanwa is cost-effective and accurate! this one can be connected with the PC.

  24. mukesh

    January 25, 2015 at 12:05 pm

    . Thanks for showing the way to trouble shoot .Warm regards . mukesh verma indore m.p.

  25. Danny

    January 25, 2015 at 1:55 pm

    very good job, your incredible, thanks

  26. suranga Electronics

    November 9, 2016 at 3:58 pm

    MR- Kushan Rnatunga,

    Well done kushan. Clever fault finding.
    good Article.


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.