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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220 Comments

  1. admin

    August 26, 2011 at 9:08 am

    HI Tipu,

    Sorry i do not have the schematic diagram. The heater winding in flyback is less thus your dick smith will measure it as short circuit. It is a good winding. Have you check the primary winding of the flyback between the B+ and the collector of HOT pins?

    Jestine

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  2. IMOH

    September 9, 2011 at 5:24 am

    What is flyback transformer & line transformer. Is ther any difference b/t them?
    2) where can i get schematic design of flyback transformer & monitor cirbuit. Am a novic in dis field. Regard

    Likes(0)Dislikes(0)
  3. admin

    September 9, 2011 at 6:40 am

    HI Imoh,

    Both are the same. Sorry i do not have schematic for flyback. Try check on the schematic link on the right navigation to look for monitor schematic.

    Jestine

    Likes(0)Dislikes(0)
  4. salman khan

    October 6, 2011 at 2:44 pm

    Dear jestine,
    Asalam-o-Alaikum,
    thanks for above information i want to ask you something like aal type
    of television fault cheaking and testing.
    please give me some advice with circut and mention with sircle hot area and output area

    Likes(0)Dislikes(0)
  5. salman khan

    October 6, 2011 at 2:50 pm

    sir,
    i want to ask you something about increasing horizental screen with choper.
    how to use choper and configration with 14" kit instal 21" sir kindly tel me about this situation

    Likes(0)Dislikes(0)
  6. admin

    October 7, 2011 at 2:56 am

    HI Salman,

    Sorry no info on this.

    Jestine

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  7. admin

    October 7, 2011 at 2:59 am

    HI Salman,

    I suggest that you visit this link:

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

    Jestine

    Likes(0)Dislikes(0)
  8. mathesh

    October 20, 2011 at 2:47 pm

    hi

    my problem is ONIDA tv MODEL: CO29OXTUA

    POWER LED ON BUT NO DISPLAY. please help me for this problem.

    Likes(0)Dislikes(0)
  9. admin

    October 21, 2011 at 2:13 am

    HI Matesh,

    CRT or LCD TV?

    Jestine

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  10. mathesh

    October 21, 2011 at 7:11 am

    hi

    my problem is ONIDA CRT TV MODEL: CO29OXTUA

    POWER LED ON BUT NO DISPLAY. please help me for this problem.

    Likes(0)Dislikes(0)
  11. admin

    October 21, 2011 at 1:39 pm

    HI Mathesh,

    No display can be cause by no high voltage or the g2 and heater circuit have problem. Does the TV have good B+ voltage and pulse signal to the HOT?

    Jestine

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  12. raymond boahen

    November 23, 2011 at 9:28 pm

    how to learn the electronic repairs and work.NOW THERE ARE ELECTRONIC AND TECHNOLOGY FOR WORKING TO IT.

    Likes(0)Dislikes(0)
  13. admin

    November 24, 2011 at 4:22 pm

    Hi Raymond,

    Get the testing electronic components ebook first at http://www.testingelectroniccomponents.com . Once you are good in testing electronic components you can start the repair work.

    Jestine

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  14. isaac sumani.

    December 6, 2011 at 8:38 pm

    i have a 29 inch crt tv that has developed a fault i.e. when i turn on it shuts down

    Likes(0)Dislikes(0)
  15. admin

    December 7, 2011 at 1:24 pm

    HI Isaac,

    Try this link to isolate the problem:

    http://www.scribd.com/doc/2957819/TT204-Identifying-television-SMPS-problems

    Jestine

    Likes(0)Dislikes(0)
  16. tatekia

    December 14, 2011 at 9:20 pm

    hi jestine I like your way of teaching but I have one question what that mean to 400v 10A 125watt this is as you know n-chanel mosfet transister discription for IRF 740 I need to know about the discription and how the watt of the transister is calculated please I'm waiting your answer as soon as your read it thank you for your help.

    Likes(0)Dislikes(0)
  17. admin

    December 16, 2011 at 7:12 am

    HI Tatekia,

    The spec is what the transistor can withstand. Sorry i do not have info how the watt can be calculated. You may need to search from those FET manufacturer website

    Jestine

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  18. bob lou

    January 2, 2012 at 7:37 am

    I used to check tv's using my Sencore Oscilloscope, just touch the probe to the collector of the HOT (output transistor) and see if the waveform is Ok. However Sencore is the only Scope I know of that is capable of doing this, try this with any other Scope and you will destroy it.

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  19. admin

    January 2, 2012 at 9:36 am

    Hi Bob,

    I use normal scope to check on the base of HOT and it is ok. To check the collector pulse i just need a probe that is rated as x100.

    Jestine

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  20. sameer

    February 23, 2012 at 2:36 pm

    hi
    dear

    TT2206 h out transister the equvalent any transister please
    (samsung ultra slim 21" tv)

    Likes(0)Dislikes(0)
  21. admin

    February 24, 2012 at 3:02 am

    HI Sameer,

    Sorry no info on this.

    Jestine

    Likes(0)Dislikes(0)
  22. ntsikelelo ivan james

    March 25, 2012 at 6:14 am

    hellow sir

    When you change the eeprom you need to programme it , what should you have to programme the eprome so that it can work good to the televion? please any image of the machine you us . I do nkow that the computor is needed plus which divice?

    Likes(0)Dislikes(0)
    • Jestine Yong

      March 26, 2012 at 9:44 am

      HI Ivan,

      First you need a good eeprom with good data so that the programmer can copy and store the data in the computer and use it to overwrite or program into a new chip. A new chip is blank and you need to program it. If you do not have the original data then you can't program it. I bought the eeprom programmer from lancos.com (Pony Prog)

      Jestine

      Likes(0)Dislikes(0)
  23. Daud Asi

    April 12, 2012 at 12:25 pm

    Sir, I always follow your instructions on electronic reparing. Now please tell me some tips on how to test / check MCU & deflection process with any kind of multimeter , weather they are good or bad. becase i have no   osscilloscope. Hope of positive response. Thanx

    Likes(0)Dislikes(0)
    • Jestine Yong

      April 12, 2012 at 11:53 pm

      HI Daud,

      For testing MCU is by using voltmeter to check on the supply voltage and scope to check on the crystal oscillator. MCU output is hard to check using analog meter and it can be checked by using digital scope. There is no way to check the output of MCU by using voltmeter. You need a scope and there is no option for that. For deflection you can refer to the link below:

      http://www.repairfaq.org/sam/deflfaq.htm

      Jestine

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  24. Daud Asi

    April 13, 2012 at 5:13 am

    Thank U so much. Sir

    Likes(0)Dislikes(0)
  25. Raju khajjidoni

    July 1, 2012 at 8:56 pm

    sir i have checked the adapter of laptop that has problem power  blink
    then i checked by the voltameter in the primary filter capacitor in the section no voltage variation and then check for secondary capacitor that has voltage variation the i have chage electolytic capcitor same value
    but problem is still

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    • Jestine Yong

      July 3, 2012 at 8:34 am

      Hi Raju,

      Did you check the e-caps with ESR meter? Is there any decayed glue (black color glue) on the board? Have you check the optoisolator ic?

      Jestine

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  26. Vans

    August 24, 2012 at 5:30 am

    sir i replace my h-out transistor and my power regulator but still my tv is dead.. it only show the LED is ligth red.. whats seems to be the problem?  more power and many thanks..godbless

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    • Jestine Yong

      August 24, 2012 at 9:51 pm

      Hi Vans,

      Red LEDs could mean the cpu or the eeprom data have problem. It could also means there is something shorted further down the circuit. The best is to check if the supply voltage is good or bad to the CPU/EEPROM. Make sure also the cpu crystal have sine wave.

      Jestine

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  27. cris

    September 7, 2012 at 10:04 am

    hi sir jestine,
    i'm new in electronics repair and i have so many questions regarding in troubleshooting but THANK YOU so much for your very informative website! Godbless!
     

    Likes(0)Dislikes(0)
    • Jestine Yong

      September 7, 2012 at 9:02 pm

      Hi Cris,

      You are welcome!

      Jestine

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  28. Nelson Caballero

    October 15, 2012 at 7:44 am

    SIR,
    Can you share to me diagram or TIPS on WS-73907 MITSUBISHI PROJECTION TV, cause the heaters are working, vertical out IC, damper, h-out, low voltage regulators, are in normal temp. B+ is ok, no burnt resistors,solders are good with no even carbon or dust on HV wires they are like new, I heared hissing static sound if I turn it off and  on, I tride my VOM test prods closed to FBT sides and I can have readings saying that I have HV same with vert. out B+ and heater lites, NO sound at all, the 3 crts are having no raster/not lit. My friend is always giving me units like this for FREE, what a waste to refuse hehe. Tnx in advance,
    Nelson Caballero
    Roswell GA USA

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    • Jestine Yong

      October 16, 2012 at 12:29 am

      Hi Nelson,

      Yes found the diagram below:

      http://elektrotanya.com/mitsubishi_v17_wt46807_ws55807_ws65807_ws55857_ws65857_ws55907_ws65907_ws73907_sm.pdf/download.html

      Jestine

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  29. mahdi

    October 24, 2012 at 2:50 am

    hello.have goodtime.i need a horizontal block diagram of CRT.can you help me?thanks

    Likes(0)Dislikes(0)
    • Jestine Yong

      October 24, 2012 at 8:52 pm

      Hi mahdi,

      Here is the link:

      http://3.bp.blogspot.com/_nKPCU2VKyDY/S7v_1oyXefI/AAAAAAAAA9I/1VstLbm2Hkk/s1600/diagram+blok+monitor.gif

      Jestine

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  30. krishna

    November 3, 2012 at 2:31 am

    sir,
    i hav one problem in crt monitor. Is that all the power supply voltages are correct but in HOT there is no present pulse voltage so eht not make so how can i solve that problem?

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    • Jestine Yong

      November 3, 2012 at 9:42 am

      HI Krishna,

      The flyback need B+ supply and the HOT base need a pulse waveform in order to work.

      Jestine

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  31. krishna

    November 7, 2012 at 8:57 am

    thank u sir,
    sir ,
    i m from nepal and i need your all books like smps reparing, crt tv reparing, mohterboard , laptop and lcd reparing. where i buy your books from nepal? is any idea about that? or if you have lecture videos i need to buy plz. because it is impossible to learn with u. plz help me

    Likes(0)Dislikes(0)
    • Jestine Yong

      November 7, 2012 at 11:19 pm

      Hi krishna,

      I have sent a personal email to you.

      Jestine

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  32. yaman

    July 6, 2013 at 3:05 am

    hello sir,
    i have old jingbow chinese tv 14", that problem is power not
    stable 110v so display also blinking. i will check with bulb series i got
    this happen but when with out bulb series check on the tv HOT is short
    what the solution for this tv ?

    Likes(0)Dislikes(0)
    • Jestine Yong

      July 6, 2013 at 11:59 am

      Hi Yaman,

      With the bulb is the voltage stable?

      Jestine

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  33. yaman

    July 6, 2013 at 6:56 pm

    hi jestine,
    no, bulb also blinking and voltage not stable

    Likes(0)Dislikes(0)
    • Jestine Yong

      July 8, 2013 at 9:47 am

      Hi Yaman,

      Bulb blinking this could mean the power supply section is the problem. Have you checked the secondary side filter capacitors?

      Jestine

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  34. yaman

    July 21, 2013 at 3:57 pm

    Hi jestine
    I would change all secondary capacitor but Problem was still not sholve some things next idia on this problem

    Likes(0)Dislikes(0)
  35. mesudmk

    July 30, 2013 at 5:12 am

    I am electronics repair man in Ethiopia.
    I have panda CRT 21" Ultra slim Tv. I have changed the board with new 21" universal board. But after a minutes the HOT become very hot & blown. I tried the board is on other 21'' normal tv screen. It is normal. Also I tried other tcl board on that Panda screen but the HOT become extremly hot. But when I replaced the yoke the screen function and no HOT become hot. But the geometry problem occured.
    I realize that the screen wants high yoke driver(HOT).
    The original board have FET ( IRF 630) that get an input from Y and support the Hot. Now my question is how I can build that ( IRF 630) Circuit externally to get HOT not blown?

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    • Jestine Yong

      July 30, 2013 at 10:09 am

      Hi Mesudmk,

      CRT Monitor/TV is very sensitive especially the Flyback, tuning circuit and the yoke coil. Replacing only the board will cause all kind of weird problems in the display and to the board. The HOT can get hot, display curve, vertical and horizontal either too wide or too small and etc. The best solution is to find another tube that has quite similar reading with the original yoke coil spec. Check the horizontal/vertical yoke coil ohm and inductance value and find a near match otherwise i do not have any other solutio for you because you are changing the nature of the well designed TV.

      Jestine

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  36. mesudmk

    July 30, 2013 at 5:52 am

    Hi Justin
    AKA I have changed the board bc the CPU 8373 have no response for key and remot. Every voltage in the board (110, 185, 25, 12, 9, 5) normal but the voltage out put for the RGB (R=1.3v G=1.3v B=9v) and 9v for Crt= 3v i.e no green and red colour. No tuning. But only blue screen.
    But the HOT is normal.
    I also changed EEPROM if the is child lock activated.
    Finally I have Changed the board. But it cant be a solution.
    Mr Justin help me on the way I can fix either the original board, Or the New board fit with the yoke. Is that possible to use 2 or more HOT in parallel, As in that of audio power ampilfier stage?

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  37. Kiran

    August 25, 2013 at 2:23 pm

    Hi Justin i have got a 21" flat igo tv. The problem is that the the height of the tv too much less. I have replace vertical ic 7840. I have replace chroma ic R2J10172HA-A97FP. i also have replace capacitors and diodes of vertical section. But i cannot increase the picture size. I have done factory settings using remote control but cannot detect the problem. Please help me

    Likes(0)Dislikes(0)
    • Jestine Yong

      August 25, 2013 at 8:21 pm

      Hi Kiran,

      Sometimes a bad vertical yoke coil could cause such problem. Check all components surrounding the vertical output ic too.

      Jestine

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  38. Kiran

    August 26, 2013 at 8:47 pm

    Hi Justin
    I replace yoke coil with a new one and now i got full screen but now i got many retrace lines on the whole screen and the menu osd also scattering, could not read a word. Iam confused. please help

    Likes(0)Dislikes(0)
    • Jestine Yong

      August 26, 2013 at 9:55 pm

      Hi Kiran,

      Perhaps the new yoke coil spec is not the same. What was the original complaint and how you detect that the yoke coil have problem?

      Jestine

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  39. Kiran

    August 26, 2013 at 11:44 pm

    Hi Justin
    Actually i had replace a new yoke and a resistor. i got full screen but there is many retrace lines and osd can be seen but scattered. So where should i check.

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  40. Kiran

    August 27, 2013 at 12:07 am

    The complaint was height very less. I replace yoke coil and a resistor 1 ohms. I got full screen but there is retrace line fully on screen and osd scattered and screen also feel like shaking. Where should i check.

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    • Jestine Yong

      August 27, 2013 at 9:31 am

      HI Kiran,

      I'm not sure if your problem is due to using the wrong type of yoke coil spec. Retrace lines can be caused bad tube, G1, G2 voltage problem and also bad components in the vertical output ic section or the vertical output ic itself.

      Jestine

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  41. Kiran

    August 27, 2013 at 9:41 pm

    Hi Jestine
    After checking thoroughly i found some pins of chroma ic loose. I resolder all pins of the ic. The base of crt was also dry soldered. I resoldered them and now i got full screen with picture. Thnks for helping.....
    And one thing do you have pin configuration of ic R2J10172HA-A97FP. i would be glad if you sent me to my email

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    • Jestine Yong

      August 28, 2013 at 9:04 am

      Hi Kiran,

      Congratulation!Sory I do not have pin configuration for the IC.

      Jestine

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  42. Kiran

    August 29, 2013 at 9:01 pm

    Hi Jestine
    I have a 21" CRT tv. When swt on there is hissing noise on the crt base of picture tube. Picture and sound normal. I have replace the LOT. But the hissing noise is still there. Is there a problem in picture tube or defect on board. Please help

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  43. Kiran

    August 29, 2013 at 9:39 pm

    Actually the hissing noise is on the final anode of LOT

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    • Jestine Yong

      August 30, 2013 at 9:21 am

      Hi kiran,

      Try clean the picture tube anode area with dry cloth.

      Jestine

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  44. Kiran

    August 31, 2013 at 5:30 pm

    I have clean the anode with cloth but hissing sound is not gone. The hissing sound seems to reduce a little. How to remove the hissing sound. Plz help

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    • Jestine Yong

      September 2, 2013 at 10:05 am

      HI Kiran,

      Since you have replaced the flyback and cleaned the area then the only thing left will be the CRT tube.

      Jestine

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  45. Kiran

    September 27, 2013 at 6:48 pm

    How can i repair wavy picture in a crt tv?

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    • Jestine Yong

      September 27, 2013 at 8:35 pm

      HI Kiran,

      There are many types of wavy picture. The most common one is the main big filter capacitor already dried up. Next check the secondary side filter capacitor.

      Jestine

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  46. Kiran

    September 28, 2013 at 8:17 pm

    There is wavy horizontal lines on the screen. Picture and sound normal. I have replaced big main filter capacitors and secondary side filter capacitors but i still got wavy lines. How to repair it.

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    • Jestine Yong

      September 29, 2013 at 8:34 am

      HI Kiran,

      If the dc supply voltage to the horizontal/vertical oscillator is good then direct replace the ic and retest. As menetioned earlier there are many factors that could cause wavy problem. A bad flyback transformer also could cause similar fault.

      Jestine

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  47. Md. Helal Kalimullah

    March 15, 2014 at 10:41 am

    Sir The h out transistor of a ONIDA ultra slim 21" crt tv repeatedly blown out as soon as switch it on.But when I open h yok shoket from it's connection point then it is ok and v line appears on the screen. I changed eht transformer,feedback capasitor,diods in related zone but no result found. please help me.

    Likes(0)Dislikes(0)
    • Jestine Yong

      March 15, 2014 at 11:57 am

      Hi Md,

      This could mean the horizontal yoke coil already have shorted winding and you need a Ring tester to check it.

      Jestine

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  48. Md. Helal Kalimullah

    March 16, 2014 at 2:29 am

    Thank you for kind information. I have tried with a normal yoke (which is used in normal type oval crt)but same result.Actually I opened the h deflexion coil from the pcb and inserted there the terminals of said yoke coil which was kept on my table departed from tube's neck.I don't know whether it was a right experiment or not. Please help me more.

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    • Jestine Yong

      March 17, 2014 at 9:36 am

      Hi Md,

      I suggest that you check the B+ dc supply since you already replaced the flyback and swapped with another yoke coil. A higher than normal B+ voltage could short the HOT. Check also for any open safety capacitor in the high voltage section.

      Jestine

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