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Why Horizontal Output Transistor In CRT Monitor Get Shorted?

By on November 2, 2007

horizontal output transistor 

There are many reasons why the horizontal output transistor (HOT) shorted in CRT Monitor.  Here are the possible cause:

HOT have life span-it can work for many years but out of a sudden it can just go shorted. Replacing only the HOT solved the probem!

Dry joints in nearby area- Yes, dry joints in the HOT leads, flyback transformer, horizontal driver circuits could cause HOT to blow.

Shorted flyback primary winding. I came across lots of HOT failure due to shorted primary winding in flyback transformer.  One of the best example was the HP 17″ 7500 CRT Monitor. Not only it blow the HOT, the B+ coil and the B+ FET blown as well!

Shorted or open internal capacitor in flyback transformer. These problems has contributed lots of HOT failure in CRT Monitor. Normally i will check the internal capacitor first before i replace the HOT and switch “ON” the Monitor.

Too high B+ voltage- A higher than normal B+ voltage will kill the HOT instantly. Make sure the B+ is supplying the right voltage to the primary winding of flyback transformer.

Running at wrong frequency- I once came across the horizontal driver circuit area was running at different frequency. It suppose to run on a 31.5 Khz (depends on resolution in your CPU setting) but  this faulty Monitor run at a too low frequency killing the HOT after “ON” for few hours!

Bad electrolytic capacitor in the supply line to horizontal driver transformer- If you found a HOT shorted make sure you check on this capacitor otherwise you may get a call back from your customer saying the Monitor not working again. The capacitor usually developed high ESR value that destroy the HOT in few hours to few weeks time.

Shorted horizontal yoke coils- A shorted horizontal yoke coil could instantly kill the HOT. I always use the dick smith flyback tester to confirm first that the yoke coil is good before the replacement of a new HOT.

Safety capacitor value out- If this safety (holddown) capacitor value dropped to zero, the high voltage produced at the anode could shoot up to over 30 kilo volt thus killing the HOT in a split of seconds.

Wrong replacement-The Monitor could be repaired by someone else and they had fitted a different specification of HOT thus making the HOT  won’t perform the best and breakdown after certain of time.

Nearby components- There are some possibilities too that the bad components nearby the HOT could cause the HOT to blow. Check the surrounding components before you switch “On” the Monitor.

Well, hope you can absorb these tips and start repairing CRT Monitor or TV with more confident! Have a brilliant day!



  1. Somashekar BS

    April 13, 2017 at 3:19 pm

    In my CRT TV always hot got failure what is da reason
    Otherwise, what things as to know to get to FX a new PCB to mine TV

    • Jestine Yong

      April 17, 2017 at 9:00 am

      Hi Somashekar,

      Just check what I have listed in the post on the reason why HOT fail. If you want to fix in a new PCB just buy the same type of PCB and fix it and retest.


    • Joseph waihenya

      March 20, 2019 at 2:15 am

      Having a super slim 29" TV,in horizontal transistor,which was plucked off,now which transistor could be placed

  2. walter

    April 25, 2017 at 12:25 pm

    Hey Jestine..I aam so eXited finding your amazing well done site.its wonderfully eplained and I'm sure I won't have any dull moment from now on.May ur legacy stay forever the way you unselfishly sharing your knowledge.So glad I've found you.Great Regards. Walter

    • Jestine Yong

      April 25, 2017 at 5:26 pm

      Hi Walter,



      • Onesmo

        August 28, 2017 at 3:56 am

        I'm new interested in electronic repair. I have my CRT tv which when turning it on the power on led/indicator id lighting but nothing on the the screen. help me sir.

        • Jestine Yong

          August 29, 2017 at 9:56 am

          Hi Onesmo,

          Have you checked if there is B+ voltage to the fyback and pulse to the base of HOT?


          • Chesco Mwandosha

            June 2, 2018 at 9:53 pm

            Thanks very much sir is real great I learn more and I'm going on.

  3. Gads

    July 5, 2017 at 1:57 am

    Flyback producing a tic tic sound even after replacing with a new one

    • Jestine Yong

      July 5, 2017 at 10:22 am

      Hi Gads,
      Can you confirm tat the sound if from flyback? Sometimes it can be from the power Transformer. Does the tic-tic sound affect the picture?


      • Gads

        July 6, 2017 at 4:29 am

        It happens when i connect it to the yorkthe fbt switch of then starts the tic tic sound

        • Jestine Yong

          July 6, 2017 at 3:46 pm

          Hi Gads,

          Can you confirm if the sound from the flyback and if the display affected by the sound?


  4. Lapologang Thebe

    July 8, 2017 at 5:26 pm

    Thanks for your comments guys it rilly help me, was confused by tic tic sound claiming its from flyback but was mistaken it was from power transformer

  5. jonas

    July 15, 2017 at 11:43 pm

    hi sir.. can you help me with my 14 inch tv ? i replace new HOT but when i sw ON ,the screen has retrace line(green) and in few seconds, the hot shorted again.. can you help me please..thanks.

    • Jestine Yong

      July 17, 2017 at 11:37 am

      Hi Jonas,

      May i know what have you checked? Did you replaced with the same type of HOT? Green retrace lines can be due to shorted green cathode or bad components in the green circuitry in the crt color board.


  6. Boris

    July 25, 2017 at 9:27 pm

    LG TV 21" Ultra slim; I 've replaced ze HOT-C2689 & Vertical IC. But the HOT is over heating. need help.

    • Jestine Yong

      July 27, 2017 at 9:56 pm

      Hi Boris,

      I suggest that you read all the steps that I have mentioned in the post. It could be one of the causes.


  7. Ganesh

    July 28, 2017 at 11:35 am

    Hi sir its very helpful for me as beginner. One doubt normally the b+ 110 voltage is OK at standby mode when try to switch on b+ volt reduced to below 50 volt what cause this problem help me thanks

    • Jestine Yong

      July 29, 2017 at 1:07 pm

      Hi Ganesh,

      Check the components along the B+ line. Check also for partial short in flyback primary winding and horizontal yoke coil. Make sure no components shorted in the secondary side of flyback transformer.


  8. jovani

    August 8, 2017 at 6:05 pm

    hello there. I have akira crt tv. it works fine except color problem. it shows red green blue colors vertically one after the other. I tried to everything but still I can't solve it. I changed the board but no change. .please help me.

    • Jestine Yong

      August 10, 2017 at 11:26 am

      HI Jovani,

      The vertical color bars are self test pattern indicating no signal present. Have you connected to a dvd player and test it out?


  9. walid

    August 12, 2017 at 10:54 pm

    hi sir...I replaced the correct HOT ...check the collector capacitors...checked the damper diode....yoke coils....but when i connect the horizontal yoke coils...then tv dont turn on...just sir

    • Jestine Yong

      August 14, 2017 at 12:17 pm

      HI WALID,

      Have you checked if the flyback get the B+ voltage? Have you checked if the base of HOT is getting a pulse waveform?


  10. marc mphepo

    October 10, 2017 at 6:15 am

    i have a china tv which came with a vertical line problem then i changed the vertical ic .i tried to switch it on the problem got solved i found out that a resistos besides flyback gets too hot and then the it starts sparking on the tube plz help

    • Jestine Yong

      October 10, 2017 at 10:02 pm

      Hi Marc,

      Probably the flyback is bad if the resistor is connected to one of the flyback pins. Without hands on assessment on the TV I would be really guessing on what might be wrong.



    November 21, 2017 at 8:58 pm


    • Jestine Yong

      November 23, 2017 at 8:34 pm

      Hi Ramesha,

      Have you checked if the power supply are producing good output voltages? Standby or blinking red LED indicator means either:

      1) MCU IC got 5 volt but cannot send out the "On" signal due to the ic itself have problem or the EEPROM IC have corrupted

      2) MCU IC could send out "On" signal but it can’t reach the main power supply section due to bad components in the optoisolator ic and surrounding components problem

      3) On signal can reach the main power supply but main power supply it self have bad components like shorted secondary diodes, bad power ic and etc.

      4) There are shorted components in the secondary side like inverter board/ mainboard and etc

      5) The DC supply input to the MCU/EEPROM IC may be improper. Make sure the DC supply is good.


      • Hlalefang

        February 24, 2021 at 4:41 am

        I am extremely happy about you Mr Jestine Yong, you are my best teacher, everytime I learn from you. I love TV repair with all my heart and I will do it. God bless you and give you many years to come.

  12. ARUN

    January 15, 2018 at 4:37 pm

    Hai sir,
    Model :Videocon slim d2h satelite tv.
    Chasis number : 21slim 249×249
    Problem :picture width extended itself and H.O.Transistor runs at very heat and keeps blows after replacement.110v is present. I changed all capacitors. It cannot be solved the problem. When i remove yoke connectors, raster appears and the H.O. Transistor works gently. So i suspect that the horizontal yoke coil may be shorted...i check that after removed yoke and i confirm that yoke coils are not burned or shorted. Because i connected 24 volt at 5 ampere load from an external transformer to individual coils of yoke and checked the voltage and temperature raising from the coils....i found that the voltage same and uniform temperature at everywere of the each individual coils....then i have assembled back and i connected except one of the horizontal yoke coil. Now tv works with normal temperature from H.O.Transistor.
    Finally i found that if i connect both of the Horizontal yoke coils together only the H.O.Transistor get heat and blows.

    Pls help me sir. Thanks in advance. Sorry for my bad english.

  13. cr maity

    March 6, 2018 at 6:33 pm

    i suffer at a lg 21" slim tv no ruster no eht when boost capacitopr original 18k. insted 18k if iused 22k cap then eht formed and one vertycal line without horizental yoke conect. when i conect horizental yoke total light off and a rush sound comes also o/p transistor making very hot icould not find the problem please helf me

  14. Chuzzy

    March 24, 2018 at 5:55 pm

    Please help me sir what is the problem this CRT TV. This TV when i on the TV it will try to start and goes in standby, it will continue like that. I open this TV and remove the plug of vertical and horizontal coil from the board the board will start normal, I switch the TV off and plug back the yoke on the board and it repeated what it was doing before.

  15. KRISHNA6876

    April 25, 2018 at 10:27 pm

    dear sir,yesterday a bezton 21'' tv is given by the customer .and said it is not powering up.a sound is suddenly came out inside the tv set due to Thunderbolt.sir,i am facing a problem that is- high b+ voltage at the HOT-Side.all voltages from the secondary rectifiers is correct.but 1 rectifier which is actually connected to 100ufd 160v capacitor.that secondary voltage from rectifier is go to power the flyback and then flyback winding pin connected to HOT BASE.hence i found high axessive voltage like 223volt at the base of the hot.hence please help me to solve the problem sir.and how to check.and what might be the culprit components.and what parts failure causes this problem please assist me sir ,thank you.

  16. Danlami williams Umaru

    July 10, 2018 at 10:07 am

    Thanks mr. Jestine this lesson was verry helpfull.

    I have (Sp)POWER SAT 499A decoder which it work but now it show red ligt only nothing more pls help me.

  17. amanuel

    September 2, 2018 at 9:57 pm

    Thank you, a bigginer will be expecting more from u.

  18. Khalid Abdul Latif

    September 21, 2018 at 2:34 am


    With respect to you and all you discussed above about frequently (HOT) shorten, another reason for this is the defected deflection ic controller which send wrong signals to the HOT driver transistor resulting in HOT conducting all the time and finally shorted.


    • Jestine Yong

      September 22, 2018 at 6:51 am

      Hi Khalid,

      Thanks for sharing.


  19. Subrat

    July 9, 2019 at 11:52 am

    HOT over heats and blows off 1 to 2 days running.

  20. Hamisu

    July 23, 2020 at 9:09 am

    Hello sir, sound issue of my lg crtv. I checked the DC voltage to my sound is Ok and I test the sound IC is ok. But up to now there is no sound. What can I do now sir? thank for your help


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