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!

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235 Comments

  1. mahesh singh

    July 1, 2014 at 9:33 am

    I have a red screen problem in my onida igo tv please suggest me how it will remove the problem.

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    • Jestine Yong

      July 1, 2014 at 4:28 pm

      Hi mahesh,

      Try check the RGB transistor and compare the Red transistor voltage/signal with Green and Blue transistor. Any different in voltage/waveform is a clue for you to troubleshoot on that area.

      Jestine

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      • mahesh singh

        July 3, 2014 at 1:51 pm

        I also replace the three transistor c-2482 but not remove the red screen problem now what i do next.

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        • Jestine Yong

          July 4, 2014 at 4:56 pm

          Compare the transistor voltage/waveform with the good one.

          Jestine

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  2. Daniel

    July 17, 2014 at 9:26 pm

    please help my TV goes off after working for some few hours completely,but when you turn it on again it works and goes off again. I have changed the HOT but no avail,i changed the vertical output too the problem is still there, what should I do?

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    • Jestine Yong

      July 18, 2014 at 8:14 pm

      HI Daniel,

      First is all the output voltages from the power supply good and stable?

      Jestine

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    • Robert

      July 19, 2014 at 10:57 am

      Hi Daniel,
      I have a 42" Sanyo LED/LCD TV that is only 1 1/2 years old and sometimes it just turns off by itself. It will come right back on when I click the remote or push the on/off button and work fine. Sometimes when it goes off & I turn it back on, it might be a month or more before it turns off again, so I'm really not worried about fixing it right now. When it starts acting up more often I'll pull the back off and see what I can find out.
      Those intermittent problems are the worst!

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  3. satish

    September 28, 2014 at 7:13 pm

    hi i have a Samsung 21" CRT TV .the problem is 'when turn on it makes ticking sound and no light no display ,just ticking noise. can anyone help?

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    • Jestine Yong

      September 29, 2014 at 10:55 am

      Probably shorted HOT or some other components.

      Jestine

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  4. alege oluwole

    October 27, 2014 at 12:32 pm

    hi i av a 32inches crt jvc product they use c5552 as HOT there and it has shorted and i cant find it here bt if i used any other HOT it get burnt imeddiately watcan i used or do pls

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    • Jestine Yong

      October 27, 2014 at 2:46 pm

      If you have checked the suggestion that I have listed in the article this means you have to use back the original part number. You can buy one from ebay.com

      Jestine

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