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PWM IC Testing Method

By on August 26, 2014








Today I want to share about External Voltage Test Method for TL494 PWM IC.  I found this method in Mr Jestine Yong’s Switch Mode Power Supply E-Book. I have applied this method in one of my customer’s working SMPS and would like to share how this checking on PWM IC can be done. First download the IC datasheet and find out which pin is the VCC, ground and output.



Once you have identified the pin outs you can start to connect the 12V DC power supply to TL494 IC VCC pins and pin No.7 (Ground) or 0V.


I hooked-up my Precise Test Lead Adaptors with IC’s Pins and powered them with my DC Variable Power Supply and connected my Handheld Oscilloscope Meter’s UNI-T UT812B positive probe to IC’s pin No. 8 & 11 and black probe was connected to DC Variable Power Supply Ground Lead.

pwm ic test

As seen in above picture the red test clip is connected to TL494 IC’s Pin No.12 and black test clip is connected to Pin No.7. My hand was holding the positive test probe of my Handheld Oscilloscope and black probe is connected to DC Variable Power Supply Ground Lead.

pwm ic tests

As seen in the above picture was the PWM waveforms and frequency. This indicates the PWM IC is working fine. If you came across a situation where you can’t get the waveform even tested it off board this suggest that the PWM IC is already bad and need replacement. If you understand well about an IC from the IC datasheet this means you can always follow the method above to check if the IC is working or not. I liked Jestine Yong testing methods and fully recommend his SMPS Repairing E-Book to all repair techs.

This article was prepared for you by Owais Akhter from Muscat Oman.


Please give a support by clicking  on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments. By the way if you have any good repair article that you want me to publish in this blog please do contact me HERE.




  1. Mark

    August 26, 2014 at 12:15 pm

    Hey Owais,
    Thanks for your article. Jestine's repairs to SMPS is an excellent book, but to be honest, I had forgotten about that section.
    I have earmarked it so that I can use that method for a SMPS that I am working on.

    Thanks again for the article.

  2. Ola' Badmos

    August 26, 2014 at 2:20 pm

    Very interesting, thank you for reminding about Jestine's tutorials, this method is very simple and reliable to use.


  3. Andre Gopee

    August 26, 2014 at 8:02 pm

    Thanks Owais, As Mark mention, I also forgot about that section.... I is a nice section on using your Oscilloscope. Thanks for sharing.

    • Humberto

      August 27, 2014 at 12:12 am

      This section is given as an extra when you buy the e-book.

  4. Tom Dunaj

    August 26, 2014 at 10:48 pm

    As always the article is a very good way to troubleshoot
    the ic chip.I like the handheld scope!

  5. Humberto

    August 27, 2014 at 12:13 am

    Good and instructive article. Thanks

  6. Juan A. Araujo

    August 27, 2014 at 1:59 am

    I have used this method several times and it worked fine.
    Thanks a lot

  7. Abdul

    August 27, 2014 at 10:57 am

    Thank you Owais.
    This article helps me, and refreshes my mind.
    I will try and refer back.
    Abdul (Singapore)

  8. tesfaye kebede

    August 28, 2014 at 10:48 am

    Thank you jestine your monthely news letter more useful for repairs and your e-book
    have a nice day to you

  9. Tim Stanford

    August 28, 2014 at 11:27 am

    I work on guitar amps and would like to see some tube amp theory. Some of the tube amps I work on have switch mode power supplies combined with tube technology. I also work on solid state amps as well.In fact my PA head broke down so I've got it on my bench . Its made by Yamaha its the EMX 512 powered mixer. It goes into protect mode as soon as I power it on. I've checked all of the final output xsistors and found no shorted out devices. But it still goes into protect mode.I'm hoping I can find the problem soon. Thanks for posting.

    • Robert

      August 29, 2014 at 2:39 am

      Hi Tim,
      There are many people that come to this website and learn, but never contribute any articles themselves.

  10. reza

    September 3, 2014 at 3:25 pm

    hello dear mr yong
    you are very good man
    you are master for me about Electronic Repair.
    good luck

  11. Raymundo Saura

    September 7, 2014 at 10:10 am

    thanks sir for sharing

  12. gourav

    October 28, 2016 at 10:37 am

    hi owasis, i wanna make a circuit that tests many type of ic.
    how can i prooceed. many types of ic like the most common used ic of 74 series
    and or not nand nor gates

  13. Godfrey Agaga

    April 22, 2017 at 12:39 pm

    please I need the best handheld oscilloscope from: The specifications, the price and how to get it from nigeria


    September 19, 2019 at 6:42 pm

    Very nice article,does the black lead of the scope go to hot ground or power supply ground, or does it go to negative lead of power supply which is different from the power supply ground.

    • Jestine Yong

      September 22, 2019 at 9:35 pm

      Hi Marco,
      If you want to check power primary side then you need to connect the scope ground (black lead) to hot ground. If you want to check the secondary side then you need to connect it to cold ground.


  15. Fred

    April 11, 2021 at 5:56 am

    Topic very instructive and helpful


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