Open Circuit In Heater (Filament) Of CRT Tube

By on May 21, 2009

crttube

After so many CRT Monitors sent in for repair, i could say that i only came across one unit of a 14″ Acer Monitor that had an open winding in the filament (heater). The complaint was no display but have high voltage and i found that the heater was present but there was no glow in the filament. Checking the filament with an ohmmeter revealed that in fact the filament already had an open circuit internally. This is very uncommon and normally the filament is quite robust.

Do you know that our filament could take about 10 to 11 volt? A normal tube is using 6.3 volt dc and by increasing the heater voltage one can bring back a tube to life but again it depends on how severe is the tube.  I had done an experiment before many years ago where i deliberately increase the heater voltage to see what voltage the filament could withstand. I tested it by using my adjustable power suppl. Increasing the voltage up to 11 volt seems to be still okay but when i set to 12 volt dc, the filament immediately break.

Now, if you ever come across any tube that have dim display and you have confirmed that the tube already weak then modify a circuit that can only go up to 10 volt. 11 volt could be marginal and the best is from 8 to 10 volt. 12 volt will surely burn up the filament. If you have the time and a bad tube (winding shorted and etc) then you can do the experiment yourself and see how is the outcome. You will see that the filament will glow extra bright before it burn out.

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74 Comments

  1. zed

    May 22, 2009 at 10:02 am

    sir can you show me how to measure the with ohmmeter the filament area.which pin? the heater pin and what pin? thanks sir. can you show a picture how to measure it.GOD BLESS YOU.

    Likes(9)Dislikes(5)
  2. admin

    May 25, 2009 at 9:19 pm

    Hi Zed,
    Use ohmmeter and measure between the H pin and ground. Some Monitor labelled it as H1 and H2. These are the filament pins.

    Jestine

    Likes(3)Dislikes(3)
  3. romy

    June 10, 2009 at 10:56 pm

    JUNE 10, 2009
    Hi Zed,
    Could you furnish me an schematic diagram of a PC power supply ATX 500W together with a troubleshooting guide. Thank You Very Much.

    Likes(2)Dislikes(3)
  4. romy

    June 10, 2009 at 11:04 pm

    ZED,
    How long will I wait for the schematic diagram and troubleshooting guide

    Likes(3)Dislikes(3)
  5. Akhilesh mishra

    December 10, 2009 at 3:04 pm

    no display in crt but E.H.T transformer is ok.

    Likes(2)Dislikes(4)
  6. Akhilesh mishra

    December 10, 2009 at 3:06 pm

    Please give a tips the cheking a fault in this condition

    Likes(3)Dislikes(1)
  7. admin

    December 11, 2009 at 5:44 am

    Hi Akhilesh,
    Try check the heater voltage(6.3 vdc) and G2 (about 250 to 300 vdc). Missing either in one of the voltage could cause no display symptom.

    Jestine

    Likes(3)Dislikes(1)
    • Irfan

      December 22, 2016 at 1:48 pm

      6.3vdc or 6.3vac?

      Likes(2)Dislikes(0)
      • Jestine Yong

        December 23, 2016 at 7:43 pm

        Hi Irfan,
        CRT TV using 6.3vac and Monitor using 6.3 volt DC

        Jestine

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  8. Michael Jackson

    November 13, 2010 at 4:07 pm

    Can We check flyback 6.3 volt without CRT, seem Flyback may bad because there has no 6.3 volt but has high voltage 27k I just bring only TV chassis and Yoke. I left CRT at my friend house. Please answer my question if CRT must be loaded to flyback will show 6.3 vol ?

    Likes(3)Dislikes(1)
  9. admin

    November 13, 2010 at 8:41 pm

    HI Michael,

    The TV 6.3 ac volt is a high pulse ac thus you can't test with normal multimeter. If you look at neck of the picture tube and if there is light then the 6.3 volt is present. If there is no light, it could be the flyback or the tube internal heater element had open circuit.

    Jestine

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  10. DHILAN

    September 28, 2012 at 1:44 pm

    DEAR SIR 
    I HAVE TROUBLE WITH PANASONIC TV SET MODEL TC-2155R ITS SOUND IS NORMAL AND NO PICTURE I TEST HIGE VOLTAGE LOOKS OK HEATER ALSO LIGHT I REMOVE YORK COILS THEN I SEE VERY DIM SPOT IN THE TUBE I MEASURE FILAMENT VOLTAGE ITS 4.5 V AC AND K 65 V DC G 250 V DC PLEASE LET ME KNOW ABOUT THIS FAULT HOW I CAN FIND WAHTS THE FILAMENT VOLTAGE MUST BE?
    THANKS SIR

    Likes(1)Dislikes(0)
    • Jestine Yong

      September 28, 2012 at 8:30 pm

      Hi Dhilah,

      Please do not remove the yoke coil. Put everything back to normal and turn higher the g2 voltage to see if the re is picture or not. Tha ac voltage is a high pulse ac thus normal multimeter can't be used to test such circuit. If you see a orange light in the tube then 90% the heater is ok.

      Jestine

      Likes(3)Dislikes(1)
  11. Dimeji

    July 29, 2013 at 4:21 pm

    Admin please help. I have a CRT that has no glow inside tube neck when put on. There is continuous hissing sound when you power on the entire unit but no display. Tested filament pins, got 5.6 ohms. Using a Fluke multimeter, (model 87V) tested the heater terminals for voltage while unit was on, got 3.2v ac. Can you advise what to do? Is the voltage supposed to be ac or dc? Is 3.2v sufficient? Thank you.

    Likes(1)Dislikes(0)
    • Jestine Yong

      July 29, 2013 at 7:50 pm

      HI Dimeji,

      Yours is a CRT TV or CRT Monitor?

      Jestine

      Likes(1)Dislikes(1)
      • Saylu

        August 14, 2017 at 8:51 pm

        Hi..
        Sir
        My Samsung crt tv on neck board not comeings proper voltage on the H1,H2,G2,R,G,or B sir please let me answere about this fault.
        Thanks sir

        Likes(0)Dislikes(1)
        • Jestine Yong

          August 16, 2017 at 9:30 pm

          Hi Saylu,

          Have you checked if the power supply output voltages good and stable?

          Jestine

          Likes(0)Dislikes(0)
  12. x3k30c

    September 2, 2013 at 7:19 am

    Great blog mister!
    I have a MAG DX700t monitor, trinitron tube. Filament voltage is 6.3v (measured with DC) resistance is around 3.2-3.4ohm orange light exist. High voltage seems to be ok though I couldn't measure it. (a main-board test point should give 500v, yet it 450v at full setting - high crisp sound and disperse blue plasma around the tube I think anode voltage is ok)

    G2 is 360v DC, G1 is -90v DC (?), HOT seems to be ok, yet there is no display.

    Once, tried to disassemble the neck of the tube (deflection etc.) but half-way I stopped, there were the RGB dots on the middle of the screen only for a while after the unit is switched on. (I forgot to attach some wires)

    G2 doesn't change when the pot is adjusted on flyback. flyback of tube defect?

    Likes(0)Dislikes(0)
    • Jestine Yong

      September 2, 2013 at 10:25 am

      G2 voltage must change when you turn the flyback knob. Try trace from the G2 wire to see if there is a resistor open circuit or not.

      Jestine

      Likes(3)Dislikes(0)
  13. x3k30c

    September 2, 2013 at 7:54 pm

    Hi Jestine,
    thanks for your comment! but i think i might have killed the flyback. There was a blue wire coming from near the flyback and as far as i remember it was connected to the chassis ground so i connected. /there were something on the display but the relay ticked for a while and everything gone. now the led is blinking when the flyback is connected. voltages ok when flyback is removed/
    Sorry for the slight off comment
    THANK YOU FOR THIS SITE

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  14. solomon eshete

    October 15, 2015 at 9:48 am

    Hi Mr Yong! I've the same problem with my 21 inch jvc tv set as the above question. My set starts the sound for a very short period of time and then stops and off timer led starts to blink,no sign of the heater or display on the screen.How could I correct it?

    Likes(1)Dislikes(1)
    • Jestine Yong

      October 15, 2015 at 9:30 pm

      HI Solomon,

      First thing you need to check if the power supply producing good and stable voltage or not. If yes, make sure the 5 volt is going to the cpu ic vcc input. Next make sure no shorted components in the B+ supply line and the HOT is good.

      Jestine

      Likes(3)Dislikes(0)
  15. solomon eshete

    October 16, 2015 at 3:19 am

    Hi mr. Yong! A 35v,1000microfarad capacitor in a 21-inch JVC TV set circuit board explodes every time I replace a new one & put the power on. I need help,Sir.

    Likes(1)Dislikes(0)
    • Jestine Yong

      October 16, 2015 at 8:43 pm

      HI Solomon,

      It could be due to bad quality of cap or the dc voltage too high.I suggest that you check the dc voltage and it should not more than 35 volt.

      Jestine

      Likes(2)Dislikes(0)
  16. solomon eshete

    October 27, 2015 at 5:55 am

    Hi Mr Yong, a CRT TV set when put on,its heater tries to start the filament and stops after showing a white light,I need your help Sir.

    Likes(2)Dislikes(1)
    • Jestine Yong

      October 27, 2015 at 7:02 am

      HI Solomon,

      Is the high voltage from the flyback still present?

      Jestine

      Likes(2)Dislikes(0)
  17. solomon eshete

    November 10, 2015 at 6:14 am

    Hi Mr.Yong ! The shorted voltage that was burning capaciters and IC transistors is solved now,it's filament shows a white light and stops when I switch it on. Shall I adjust the screen knob at the flyback to increase the G2 voltage?

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    • Jestine Yong

      November 10, 2015 at 10:31 am

      HI Solomon,

      A working filament should light up and you can adjust the G2 voltage to get the right brightness you need.

      Jestine

      Likes(4)Dislikes(0)
  18. Solomon Eshete

    November 25, 2015 at 9:20 pm

    Hi Mr. Yong, What could the real cause a blurred image display of a TV set after a damaged IC transistor is changed? I'm grateful to you Sir.!

    Likes(0)Dislikes(0)
    • Jestine Yong

      November 27, 2015 at 9:29 am

      Hi Solomon,

      Blur display is usually caused bad flyback or pc tube. Try adjust the flyback focus knob first and see how it goes.

      Jestine

      Likes(1)Dislikes(0)
  19. Arnold

    December 12, 2015 at 8:57 am

    Hi sir jestine.
    How many ohms of each RGB filament of CRT TV 21inch

    Thanks.
    Arnold

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    • Jestine Yong

      December 12, 2015 at 12:22 pm

      Hi Arnold,

      There is usually only one filament and it should be about 4 to 7 Ohm.

      Jestine

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  20. Jodi

    February 25, 2016 at 5:26 am

    Hi...I recently picked up a sony pvm-2530. It is missing red and blue, but shows green images...and they are dim. If jumper with 10k resistor to ground, green goes brighter...jumper to red or blue..nothing. Transistors for rgb on neck board all show same voltage. And voltage at rgb pins show 65-70vdc

    Likes(1)Dislikes(0)
    • Jestine Yong

      February 25, 2016 at 10:25 am

      Hi Jodi,

      Probably the two guns could have been very weak. Try visit the link below and read through it as there is a way to brighten up the tube:

      http://www.repairfaq.org/samnew/tvfaq/tvncbwp.htm

      Jestine

      Likes(1)Dislikes(0)
  21. romel

    July 9, 2016 at 3:57 pm

    Mr Jestine hi there! How could i know that the H.O.T in tv is faulty? Pls give advice admin...i am very grateful 2u sir

    Likes(0)Dislikes(0)
    • Jestine Yong

      July 11, 2016 at 10:04 am

      Hi Romel,

      You need to remove the HOT and test it with your ohmmeter.

      Jestine

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  22. Jayandhran Seenandan

    July 16, 2016 at 2:49 am

    Hi I hav an Akashi cxrt tv. I got I t working. The problem is the colur is black n white on start up , but if u shake the board the colour cums. I suspect a dry joint , but I canot find it. Please advise. Thank u.

    Likes(0)Dislikes(0)
    • Jestine Yong

      July 16, 2016 at 10:06 am

      Hi Jayandhran,

      Try resolder the IC and crystal oscillator area.

      Jestine

      Likes(0)Dislikes(0)
  23. girmachew

    September 3, 2016 at 11:41 am

    My name is girmachew

    I have a superfine crt tv
    When I turned on it takes several minutes what should I do

    Likes(0)Dislikes(0)
    • Jestine Yong

      September 5, 2016 at 10:58 am

      HI Girmachew,

      It can be due to weak tube or the G2 voltage not high enough. If G2 voltage is not high enough, it can be due to bad flyback or the G2 line have leaky component or even decayed glue.

      Jestine

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  24. Benjamin D

    September 3, 2016 at 2:48 pm

    Hello sir, I was looking through a 29" KONKA CRT TV, it suddenly stops, there is no orange light on the CRT tube or no high voltage on the anode although the HOT is changed. Is that a detective flyback? I need your support sir.
    Thank you

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    • Jestine Yong

      September 5, 2016 at 11:32 am

      Hi Benjamin,

      You need to check if there is pulse to the base of HOT or not. If no pulse then the flyback will not be energized.

      Jestine

      Likes(2)Dislikes(0)
  25. johhn alex

    September 30, 2016 at 9:17 am

    hi sir yong can you please help me in jvc av21va15 no power continues blinking only..complete b+ and other supply as i check the voltage..i replace vertical ic caps and HOT i also done resolder.need your advice or schematic diagram for this unit.tnx
    and God bless

    Likes(0)Dislikes(0)
    • Jestine Yong

      October 2, 2016 at 4:29 pm

      Hi John,
      Sorry i do not keep schematic. Have you isolate the B+ line? Blinking can be caused by power section or failure in high voltage section.

      Jestine

      Likes(1)Dislikes(0)
      • johhn alex

        October 2, 2016 at 5:52 pm

        hI sir yong,

        The b+ supply is normal and there is oscillation but the protect circuit keep the unit shutoff after few second.Can i bypass the protect sir OR do you have any suggestion regarding this problem.

        thx

        john

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        • Jestine Yong

          October 5, 2016 at 9:39 am

          HI Johhn,

          You cannot bypass the circuit-it is too dangerous as the high level of Xray can harm the user. You need to find out the fault why it shutdown. Can it be caused by the power supply itself or the high voltage circuit like a broken flyback transformer.

          Jestine

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  26. Sfiso

    October 8, 2016 at 6:44 pm

    Hi jestine
    My tv has a display problem, there is no red on screen I have blue and green but red is very dim, I tested power on the pins there is voltage on all three Red, Green and blue and no dry solder voltage is around 169 DC, everything works fine only red is very dim and I adjusted the colur settings no change... TV is SINOTEC 54cm

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    • Jestine Yong

      October 8, 2016 at 10:34 pm

      Hi Sfiso,

      Red dim can be due to weak red gun or bad capacitors in the CRT board.

      Jestine

      Likes(0)Dislikes(0)
  27. Amandeep

    November 29, 2016 at 12:02 am

    Dear Sir
    Warm greetings of the day

    My tv have display problem. There is only contrast problem.
    From the service menu i have adjusted the BW balance and increased the contrast. But still picture is Dim. Kindly give a suitable resolution.

    Likes(0)Dislikes(0)
    • Jestine Yong

      November 29, 2016 at 8:18 am

      Hi Amandeep,

      Picture dim can be caused by weak picture tube. If the G2, g1 voltage check to be good and heater have a bright light then most probably the tube is weak. However, sometimes it can be caused by failure in the contrast circuit or even bad eeprom ic data.
      Jestine

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  28. dodong

    December 24, 2016 at 3:10 pm

    sir jestine
    is there other ways to make the crt tv sharper image cause i already adjusted the full clockwise, the image is still blurred. Thanks

    Likes(0)Dislikes(0)
    • Jestine Yong

      December 25, 2016 at 7:27 pm

      Hi Dodong,
      If adjust the flyback screen focus still can't make it sharp then the tube have problem.

      Jestine

      Likes(0)Dislikes(0)
  29. Varun Sharma

    December 28, 2016 at 11:01 pm

    There is no heater glow in my CRT TV. What to do sir how could i repair it... ??? Actually i accidentally shorted the 180 terminal and the heater terminal on the CRT PCB. after that there was no display.Please help me solve this problem.

    Likes(0)Dislikes(0)
    • Jestine Yong

      December 30, 2016 at 12:32 pm

      Hi Varun,

      The flyback has to work first in order to see the heater light. Have you checked if the flyback is receiving the B+ voltage and a waveform to the base of HOT? If the flyback don't work there will be no display.

      Jestine

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  30. Manen

    February 3, 2017 at 5:37 pm

    Hi Mr yong,
    I have a 21 inch crt tv with the picture problem, so i try to checked heater voltage and i got it only 1 volt ac. Is it normal?
    thank you

    Likes(0)Dislikes(0)
    • Jestine Yong

      February 4, 2017 at 10:35 am

      Hi Manen,

      TV heater voltage is high frequency ac so your normal multimeter not be able to check it. If you can see an orange light in the tube probably there is an ac voltage.

      Jestine

      Likes(1)Dislikes(1)
  31. Mina

    February 27, 2017 at 2:46 am

    hello
    i have compaq 7500 monitor the problem is no display
    i check the voltage on heater found G1 =-27
    and G2= 270
    and HOT okay but it be hot fast when i turn on monitor
    i think i have a problem in G1 please help me to solve this problem

    Likes(0)Dislikes(0)
    • Jestine Yong

      February 27, 2017 at 7:57 am

      Hi Mina,

      What is the heater dc voltage? Have you tried increase the G2 voltage to 300 vdc?

      Jestine

      Likes(1)Dislikes(0)
      • Mina

        February 27, 2017 at 10:19 pm

        it's 6.7 volt and i tried to increase volt of G2 to 285 volt but Hot transistor become very hot in short time

        Likes(0)Dislikes(0)
        • Jestine Yong

          February 28, 2017 at 7:27 am

          Hi Mina,

          Ok noted. When you adjust the brightness did the G1 Voltage vary? Is there a resistance when you measure the heater filament voltage?

          Jestine

          Likes(1)Dislikes(0)
          • Mina

            February 28, 2017 at 5:20 pm

            The G1 don't vary
            which resistance ?!

            Likes(0)Dislikes(0)
            • Jestine Yong

              March 1, 2017 at 3:34 pm

              Hi Mina,

              You have to track from G1.It can be resistor problem, leaky transistor, bad capacitor or even corrupted eeprom ic data.

              Jestine

              Likes(1)Dislikes(0)
              • Mina

                March 1, 2017 at 6:02 pm

                i found two track to G1 on monitor one on the main board and another in socket of the CRT
                but i think found another problem cause the HOT be more hot in short time
                can u help me by monitor circuit

                Likes(0)Dislikes(0)
                • Jestine Yong

                  March 1, 2017 at 9:23 pm

                  Hi Mina,

                  Sorry I do not have monitor circuit.

                  Jestine

                  Likes(1)Dislikes(0)
  32. Mina

    March 2, 2017 at 4:54 am

    MR young how i measure the volt of line oin 3&4&5&6&7&8&9&10
    ac or dc and i think there is short between 3&4&5&6&8&10 this pins and the ground
    this natural ??!

    Likes(0)Dislikes(0)
    • Jestine Yong

      March 7, 2017 at 8:15 am

      Hi Mina,

      Sorry i don't understand your question. Can you elaborate?

      Jestine

      Likes(0)Dislikes(0)
  33. Nader

    March 8, 2017 at 2:20 am

    hello
    how can i measure the volts of power transformer
    how i can measure it by put voltmeter on Ac or dc and put the black electrode and red electrode on what to measure the power volts of the transformer
    and what the value of this volts for CRT monitor 17 in

    Likes(0)Dislikes(0)
  34. randy dolot

    June 8, 2017 at 9:53 am

    Sir lg CRT tv 21 if you float the fuseble resistor of heater it doesnt shutoff if you connect it will shutoff.where is the trouble pls help me.

    Likes(0)Dislikes(0)
    • Jestine Yong

      June 12, 2017 at 10:04 am

      Hi Randy,

      Power shut off wit no power Led light or the display/raster shut off?

      Jestine

      Likes(0)Dislikes(0)
  35. Daniel

    June 29, 2017 at 2:46 am

    Hi, i need to change the control of a CTR monitor and use another source. I'm glad if someone helps me.

    Likes(0)Dislikes(0)
  36. Daniel

    July 13, 2017 at 12:58 am

    Hi, I need to change the control of a CTR of my monitor, how can i do it? I mean, i understand that i need 3 sources to source that can replace the fly back and 2 more one for heater and another for focus and the colors ... is it possible? It is for a experimental subject of my university

    Likes(0)Dislikes(0)
    • Jestine Yong

      July 14, 2017 at 10:08 am

      Hi Daniel,

      May i know what kind of control do you want to change in your CRT Monitor?

      Jestine

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  37. Akbar Gondal

    October 17, 2017 at 5:16 pm

    Salaam,
    Brother Jestin i have repairing shop in Pakistan .
    One LCD Sony model number 40BX400.There is sound ok but no picture or display.can chang channals.can you help me to resolve this problam ?
    Thanks
    Regard
    Akbar

    Likes(0)Dislikes(0)
    • Jestine Yong

      October 17, 2017 at 9:11 pm

      Hi Akbar,

      It could be the T-con board controller IC fault. Without hands on assessment I would be really guessing on what might be wrong. I wish I could be of more help.

      Jestine

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