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How To Prevent The Horizontal Output Transistor (H.O.T) From Getting Shorted After Replacement

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horizontal output transistor

Horizontal Output Transistor In A Tv Board

Naturally you replace the shorted transistor with a new one and you power on the Television and it come up beautifully, and before you begin to celebrate the television goes down again(stop working)

You open the set and after checking the health of the same component (H.O.T) you find alas it is shorted again!!

This problem of H.O.T getting shorted immediately or after some times of replacement has given many technicians sleepless night trying to figure out what is happening here!!

In this article I am going to give you some tips on what to do to prevent the H.O.T from getting shorted after replacement.

To minimize the chances of the HOT getting shorted please make it a practice to change the following components directly every time you do H.O.T replacement.

high voltage tv circuit

A Typical High Voltage Circuit In CRT TV

High on the list is the snubber capacitor; this is also called the safety capacitor.

Sometimes it may also open, short or change its capacitance value and this always have effect on the H.O.T.

Next are the dry joints around the horizontal drive and output components, please make it a practice to do re-soldering around these components including the fly back pins, Horizontal drive transformer pins every time you find the HOT shorted.

The drive transistor should be replaced directly without even measuring it, sometimes it develop some leakage and hence cause the H.O.T to short after a period of time.

Also be sure to check the ESR of the filter capacitors involved in filtering the supply to horizontal circuits and if you suspect any just directly replace that capacitor.

horizontal drive circuit

A Typical Horizontal Driver And HOT Circuit

In some television like the JVC they incorporate some component on path to the base of the HOT (usually a Capacitor and choke) please be sure to replace them directly.

If still the HOT is getting shorted then finally you may have to change the fly back transformer or the horizontal oscillator IC is messed up and need replacement.

 

crt tv repair

CRT TV Repair By Humphrey

Humphrey Kimathi, Electronics repair based at Nairobi Kenya, Author CRT television repair Course, for more info please visit my blog at: http://www.humphreykimathi.blogspot.com

This article was prepared for you by Humphrey Kimathi, one of our 'Master Authors'.
Visit this authors profile page and learn more about them & the articles they write.

Published in our category of CRT Televisions on Monday May 16, 2011 with the keywords , , , , , , , , , .
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25 Comments

  1. Dimo Dimow
    Posted Thursday June 2, 2011 at 6:08 pm | Permalink

    Златни правила , ще добавя още едно +В=110V да е константа във времето .При +В повече от 110v след време води също до дефект на транзистора.Да се проверява и C3- филтъра на +В .
    Полезна статия . Благодаря !
    Превод от български на английски
    Golden rules will add another + B = 110V is constant over time. In + In more than 110v, in time also leads to a defect in tranzistora.Da checked and C3-+ B filter.
    Useful article. THANKS !

  2. Henry Mayanja
    Posted Wednesday June 8, 2011 at 11:36 am | Permalink

    A very educative and useful article.

    Henry

  3. Roy Martin
    Posted Saturday June 11, 2011 at 6:30 pm | Permalink

    In addition to your tip; you can also remove the cathode cap from the picture tube but be careful and isolate it for your own safety, dont forget to discharge it first before you begin any step further, thus preventing any more damage to other components like the low voltage power supply or even the horizontal output section. As a general rule: you have to replace both the fast recovery diode and the hor. Out capacitor aside fm the hor. Out transistor. Hope this tip helps.

    • Jestine Yong
      Posted Sunday June 12, 2011 at 12:30 am | Permalink

      Thanks for sharing your tip!

      Jestine

  4. Badea Mircea
    Posted Sunday June 12, 2011 at 4:28 pm | Permalink

    The cause of the destruction of that transistor is short circuit in the deflection coil. Newer components circulate counterfeit market.

    • Posted Monday June 13, 2011 at 7:46 am | Permalink

      Absolutely Right Badea, I think i missed that out….Thanks for picking it up…Regards Humphrey

  5. ramboo cabrera
    Posted Thursday June 16, 2011 at 4:33 am | Permalink

    what is the purpose of snubber capacitor?

  6. Posted Friday June 17, 2011 at 8:04 am | Permalink

    Basically Snubber Capacitor is used to suppress (snub) induced high voltages by the collapsing magnetic field in the flyback transformer primary winding which could otherwise lead to destruction of the Horizontal output transistor (HOT).

    That is why sometimes this capacitor is also referred to as "safety capacitor". If this capacitor is open or is removed from the circuit it will cause instant destruction of H.O.T transistor.

    Hope I have answered your question Ramboo
    Regards Humphrey

    • bob lou
      Posted Sunday July 3, 2011 at 2:18 pm | Permalink

      I think the Snubber does the same thing that the Damper tube did in the very old tv’s years ago.

      And what’s that large orange Capacitor next to the Snubber?

  7. Badea Mircea
    Posted Friday June 17, 2011 at 2:04 pm | Permalink

    A typical defect is C523 condenser drying . We recommend replacing a capacitor with low ESR

  8. Posted Tuesday July 5, 2011 at 12:01 pm | Permalink

    Hi Bob,
    The large Orange Capacitor next to the Snubber is called the S-Correction Capacitor; the voltage rating for this capacitor is usually between 250V-400Vvolts. It is usually placed in series with the horizontal deflection coil and linearity coil. As the name implies it is used to correct the saw tooth waveform into a slightly sine waveform. About the Snubber & Damper tube being related I would not know but if it was placed at the same point (across the Collector and Emitter of the H.O.T then I guess it was to serve the same purpose)

    • bob lou
      Posted Friday July 8, 2011 at 10:27 pm | Permalink

      Thanks for your reply…I started learning tv repair many years ago when we had vacuum tubes. I learned to how to identify each tube and explain what it’s purpose was.

  9. Rolando Salgado
    Posted Sunday July 17, 2011 at 7:08 pm | Permalink

    Very important tips, with this failure, thanks for share your experience, Rolando

    • Posted Monday July 18, 2011 at 2:25 pm | Permalink

      Hi Rolando.
      Thank you for your feedback Rolando, and for passing by the Best electronics articles dot com.

      Regards Humphrey

  10. philip
    Posted Wednesday August 17, 2011 at 4:35 am | Permalink

    sir id like to know how to check the ABL? thanks

    • Posted Wednesday August 17, 2011 at 5:34 am | Permalink

      Hi Philip, Check out my latest book on CRT Television repair course on how to test the ABL circuit and much more!!!

      Regards Humphrey

  11. jgmanza
    Posted Wednesday October 5, 2011 at 9:36 pm | Permalink

    I recommend the book. Exactly what I need from so long ago, I always wondered where the Vertical and Horizontal yoke were, what they do and how to easily find the vertical IC, by the time I finish with this, I will be ready for the LCD Monitor repair book.

    • Posted Friday October 7, 2011 at 7:12 am | Permalink

      Thanks for your compliment on my latest book on CRT television repair Course Mr. JGManza. I hope you will find the book a valuable companion on your work bench.

      Regards Humphrey

  12. sugenk
    Posted Wednesday November 2, 2011 at 5:58 pm | Permalink

    Im just add somewords to share in replacing H.O.T. when I replace it Im always cut the pcb trace that directly to +B for the horisntal section suplly in the secondary regulator. Measure a change values of +B it can be increasing and must be adjusted to a proper value (marked on PCB). this can be more safely for next step without a higher risk. And I sometimes replace a damaged H.O.T with a stronger ones ( use 20in HOT for 14in HOT) but its your choice. I hope this may usefull. thanx mrHumprey.

    • Posted Monday November 7, 2011 at 5:49 am | Permalink

      Hi Sugenk,

      Thanks for your contribution on this lesson, maybe to add a little is that it is very important to dis-connect the B+ load after the feedback circuit otherwise the power supply may increase a lot and even end up destroying other components on the primary power supply (that is why it in not recommended to power on TV without the opto-coupler which is part of feedback circuit removed from the circuit), on the last part of your comment again I would highly recommend exact replacement of the H.O.T for safety reasons.

      Regards Humphrey

  13. Ahmad Nasir Mohamad
    Posted Saturday December 31, 2011 at 10:33 am | Permalink

    I wish I could be your student Mr Humphrey…..

    • Posted Wednesday January 4, 2012 at 6:55 am | Permalink

      Hi Ahmad,
      Thanks for your kind words, I too would not mind having a student full of enthusiasm like you in my class, having said that let me point out that at the moment i am not offering any online course but i have written a book on troubleshooting and repair of CRT color television, for more details you can click on the book cover elsewhere on this post.

      Regards Humphrey

  14. bogie
    Posted Sunday January 22, 2012 at 5:19 pm | Permalink

    Well good for you,but for me as a beginner i’m still in the dark cloud. Yah..I bought the book and learn something but what i need is a simple or typical block diagram of crt tv and explain how those section work. Because i’m having a hard time staring on the diagrams circuit without knowing the function of it is like a suiside for me. Anybody can share their idea…..

    • Posted Wednesday January 25, 2012 at 6:55 am | Permalink

      Hi Bogie,
      Thanks for your feedback Bogie, on the issue of having a simple block diagram of CRT TV and explain how those section work, i think this is all about this book evolve around.

      Instead of having on full circuit diagram of the CRT TV, we have broken it into sections(blocks) where we explain the section basic functions and common problems associated with that block.

      By the time you are through with the book you will have covered the 18 major blocks in CRT Television which will give you the full picture of the CRT Television.

      On the issue of how these section work i am sure we have done our best by use of circuit diagram of the sections plus a colored photo of the component in the actual circuit and what happens when those components fail.

      Regards Humphrey

  15. isidro tan
    Posted Saturday March 3, 2012 at 8:56 am | Permalink

    Good day sir, thank you for the explanation and technique on replacing H.O.T, I had been servicing CRT, back home and have same problem, your explanation will be a great help for us. Thank you.

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