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How To Test Horizontal Driver Transformer

By on April 7, 2008

If you have the flyback tester then it would be easy for you to test the horizontal driver transformer. The testing method is the same as when you test on the smps transformer. The horizontal driver transformer primary winding is not as high as the smps transformer thus you cannot expect it to show many LED bar from the test. A good one sometime only shows one bar while to some it may go up to few LED bars.


Test also the primary and secondary winding with ohmmeter just to make sure the winding is not broken internally. Secondary winding have very less turn thus your result is the LED bar may not light up at all! Please take note of this and do not think that it has problem. I have repaired thousands of CRT Monitors and so far i have only seen few bad horizontal driver transformer  and the problem was open circuit in the primary winding.

Well, hope with this repair tips, you can easily test horizontal driver transformer less than a minute. Take care bro!



  1. Kayden

    July 26, 2016 at 11:05 am

    You stated that you had seen faults where the primary winding was broken. Was the fault fixed by simply replacing the transformer or is there other components that will cause the transformer to fail again?


    • Jestine Yong

      July 28, 2016 at 5:29 pm

      Hi Kayden,
      Yes, only the replacement of the transformer solved the problem and no other components found to be faulty.


  2. dalganjan kurre

    March 1, 2017 at 10:35 pm

    sir i have a crt tv with picture shaking verticaly and when i open and see the supply voltage to pin 2 of la78040 ic i faund normal voltage and i also found that this supply voltage is also going to horizontal triver transformer please help me.

    • Jestine Yong

      March 7, 2017 at 8:14 am

      Hi Dalganjan,

      Vertical shaking can be caused by many factors. If I did not see the TV display problem myself, it is hard to tell where should start first. It can be caused by bad vertical oscillator ic, unstable dc supply output voltage from power supply, dry joints, bad components and etc.


  3. Bizimungu Jonathan

    April 5, 2018 at 3:09 pm

    hi sir.

    my crt tv(sharp) fails to turn on.for the first time,the fuse blew out,,when i replaced another it also had blown as well,,,then i started troubleshooting,(in SMPS power supply) i saw a switching transistor whose pins were shorted, i replaced it,as well as it's closest transistor(high beta) but then,the fuse could no longer blow out,as it was before,,,but still the tv is not yet on,,,a smoothing capacitor has no symptoms.

    i wonder your help please

    • Jestine Yong

      April 10, 2018 at 8:25 pm

      Hi Bizimungu,

      I suggest that you check all the components in the power primary and secondary output side. If all components checked to be good then direct replace the power IC and retest.


  4. Tyrone

    June 10, 2018 at 11:48 pm

    Hi sir
    How do you get a part number for a horizontal driver Transformer and secondly my HOT keep on shorting without blowing a fuse. Please help

    • Jestine Yong

      June 13, 2018 at 9:17 am

      Hi Tyrone,

      The part number is written on top of the transformer. Please visit the link below to check why HOT always burnt:


      • Lwandile Maseti

        October 15, 2021 at 10:37 am

        Am I correct if I say that the Horizontal Output Transistor (HOT) has nothing to do with a blowing fuse of a Cathode Ray Tube television's (CRT TV) SMPS, sir?

        • Jestine Yong

          October 16, 2021 at 12:30 pm

          Hi Lwandile,
          Yes, usually would not blow a fuse, it only cause power supply not to start up (shutdown mode). If there is a protection fuse along the B+ line then it would usually open circuit.



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