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PWM IC Tester

By on July 22, 2009

One of my EGR members from Iran had completed the project of building the UC3842 PWM IC tester. I like the sticker that have all the PWM IC part number (refer to the photo). It is good to have this tester as it could show you whether the PWM IC is in good condition or not. Usually when a power FET or the zener diode have problem we just directly replace the power IC without knowing 100% if it good or bad. And we dare not test the PWM IC together with the new power FET because if the power IC have problem it will surely blow the power FET again. Thus by having this tester you will have a piece of mind of not to worry again if the existing PWM IC will blow the power FET. If you have not access to this project you can click on the photo to visit the website.

ic tester



  1. John Preher

    July 23, 2009 at 3:21 am

    nice, this is a cool little device for sure...

  2. admin

    July 23, 2009 at 7:28 pm

    HI John,

    Hope you could build one too!


  3. wahid

    October 14, 2009 at 4:55 am

    thanks for your hard work.
    i hope to help me for repair the power supply (hp.pentium4)
    i change all primary elements with the i c UC3845 and when i make power on all things be bad(explos).

  4. admin

    October 14, 2009 at 8:57 pm

    Hi Wahid,

    Have you check all components in the power section? Usually when power ic have problem the power FET may also faulty.


  5. Wahid

    October 15, 2009 at 10:32 pm

    HI Jestine
    Thank you Mr J for your answer.
    I have changed the power FET (9N 90c)by another power Fet(7N..).
    the power supply still wrong.

  6. admin

    October 16, 2009 at 7:20 am

    Hi Wahid,

    The FET that start with 9N something is 900volt and the one you have replaced 7N .. was 700 Volt. It may not be compatible and you have to check all components in the power side and test the primary winding of the transformer as well. Have you test the supply voltage to power IC?


  7. wahid

    October 17, 2009 at 6:40 am

    I chandeg all components excpte the FET (9N90C).I dont find the some one compatible to the FET.
    I cant test the supply voltage because when i make the boutom on the power supply all the power IC and some tr explosed.

  8. sokhon

    December 4, 2010 at 10:38 pm

    i want to know how to test ic uc3845 it good or bad

  9. admin

    December 4, 2010 at 11:34 pm

    HI Sokhon,

    You can use the the above ic tester or oscilloscope.


  10. Laurens Sierdsma

    March 26, 2011 at 3:49 am

    Dear Jestine,

    Unfortunately the link for the schematic of the PWM tester did not work. Can you send us the schematic by mail?

    Kind regards,

    Laurens Sierdsma
    The Netherlands

  11. admin

    March 28, 2011 at 5:54 am

    HI Lauren,

    Sorry, the article i have removed it to make it as a bonus report for buyer of the smps repair ebook at


  12. pakdhe

    July 17, 2011 at 3:48 pm

    Hai Jestine, can you show me the schematic diagram of PWM IC Tester above? I want to make it as my project for my self. Thanks.

  13. admin

    July 18, 2011 at 9:13 pm

    HI Pakdhe,

    I have made this as a report in this website


  14. salman

    September 29, 2012 at 12:36 pm

    sir i want IC tester for 62 legs

    • Jestine Yong

      September 29, 2012 at 8:57 pm

      Hi Salman,

      Sorry no info on ic tester for 62 legs.


  15. Peter

    November 20, 2012 at 10:03 am

    Hi Jestine,
    I think this link are broken now
    I gat this message
    Not Found
    The requested document was not found on this server.

    Web Server at

    • Jestine Yong

      November 20, 2012 at 10:57 pm

      Hi Peter,

      I guss I have removed it to put it as a bonus ion the power supply repair ebook.


  16. Evan Evans

    December 27, 2014 at 11:17 pm

    Yes, it would be a handy unit to build and use but the website underlying the photo DOES NOT EXIST!


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