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Focus Problem In CRT TV

By on August 3, 2013

I’m having some difficulty in repairing a 21″ sharp tv. It has focus problem so making it show blurred images. I have tried to adjust the focus knot of the flyback transformer but it remains the same. The components around the horizontal and vertical deflection stages are working fine.what are your suggestions sir. Could the flyback transformer, the stan-coil, or the CRT cause this. I’m confused please help me.


The problem usually is due to the either bad flyback transformer or bad CRT tube. If after adjustment of the focus knob at the flyback transformer and it slowly go blur again then most likely is the flyback problem.





  1. Frank

    August 20, 2015 at 3:10 am

    Hello sir am glad that through your posting am becoming a pro in crt tv repair am also happy to tell you that i fixed the colour patches problem i met. I only replaced the posistor and it worked fine but I met a crt tv SHAECO there is too much green color red is present and alittle blue white picture is displaying cream white. I changed all the RGB and all the three big resistors but no change.

    • Jestine Yong

      August 21, 2015 at 8:37 pm

      Hi Frank,

      Have you tried the menu setting? Have you checked the e-caps in the crt board?


  2. linclon

    July 16, 2016 at 6:12 pm

    hallo sir im busy repairing lg crt tv model cf29h30 it have a focus problem when i turnup the grid voltage at lopty the picture goes fuzzy uot of focus. when i turn down the grid voltage the picture is ok but very dark. tv have dual focus

    • Jestine Yong

      July 18, 2016 at 1:28 pm

      HI Lincoln,

      The picture could be weak already. If you have the high voltage probe then it would easy to detect if the flyback or the tube problem. Just measure the focus pin and see if it is low, normal or slowly goes up. It should be stable.


  3. A

    May 16, 2017 at 4:40 pm

    i also have a problem with mine..its sony crt..displays horizontal lines in the entire screen & th image is blured...

    • A

      May 16, 2017 at 4:47 pm

      The focus & brghtnes knobs are locate on th board attached to the they cant focus..nid asistance kindly

    • Jestine Yong

      May 18, 2017 at 9:09 pm

      Hi A,

      Please visit this link

      to solve horizontal line problem and if the focus can't be adjusted probably the tube could be weak already.


  4. jeotham

    June 11, 2018 at 1:19 pm

    have a good day sir, i got a trouble here in my crt tv sanyo st-21se1v, when i started the tv, a white screen appear then after 5mins or so, the screen slowly appear to be normal...if i turned it off then after several mins start the tv again, it operates normally, what might be the problem sir?flyback?
    the b+ voltage in the first start up is 140v, and it will go down to 130v as the screen is normal....could you give some ideas sir?

    jeotham of cebu, phils.

    • Jestine Yong

      June 13, 2018 at 9:21 am

      Hi Jeotham,

      Usually is the flyback problem but it can also be caused by bad CRT socket and weak picture tube.


  5. Amey Bhavsar

    November 10, 2018 at 1:22 am

    Hello, i was repairing the my CRT tv at home. I have replaced the board inside it due to issues of not turning on.
    Now after turning on, it shows red, blue, green strips and white strips across the screen.
    Also the image from the set-top box is also a little blurry.
    I have tried adjusting the knob at the back, but nothing seems to work. Some changes happen, but it doesnt go back to focused.

    • Jestine Yong

      November 12, 2018 at 8:15 pm


      If the CRT TV display is blur even after you have adjusted the focus knob this could means the CRT Tube is weak. Sometimes it can be the flyback divider fault (screen and the focus variable resistor problem).


  6. OSCAR

    June 22, 2019 at 11:46 am

    am working on a crt tv,at first it brings visible retrace horizontal line allover the screen with poor picture,i suspected it to flyback transf after replacing flyback,it tried to work normal,i switch it off clear some dry joint on crt board but i made mistake to power tv without pining the main ground frm crt to tube board then everything became not gud to power tv without attaching that black wire frm crt to tube boad

  7. sal

    July 8, 2019 at 2:26 pm

    my CRT tv has negative pictures on each picture shown but I have tried to replace with new flybacks but remained. may I be helped

  8. Kareem G Williams

    July 20, 2019 at 11:16 pm

    I have a 18 turning 19 year old SONY Trinitron CRT TV KV-27S42 It currently has a Color problem and the sharpness keeps going in and out when I turn the T.V. off the picture comes back clear dispite the colors then a few minutes later it goes back blurry I would like some answers please if anyone can respond back

  9. edward

    June 2, 2020 at 3:37 pm

    how can i fix eeprom error on a crt tv

    • Jestine Yong

      June 3, 2020 at 9:51 am

      Hi Edward,

      Please visit this link:



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