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CRT TV Color Patches Problem Solved

By on October 21, 2014

 

 

 

 

 

 

 

 

 

A friend of mine called me concerning his CRT TV problem. The complaint was about not getting proper color on the TV screen. I went to his place and checked the TV and I found it was color patches problem. The color was uneven as seen from the below picture:

 crt tv repair

As per my assumption, this symptom points to two possible faulty stages.

One is degaussing circuit and second is CRT Tube itself. I opened up the TV to check on the degaussing circuit first. It has only two parts i.e. the degaussing coil and a posistor (PTC).

crt tv repairs

I removed the degaussing coil from the connector and checked it with my Ohmmeter. I got 18 Ohm and this means it does not have open circuit. The next test was on the posistor (A Posistor is a resistor that connects in series with the degaussing coil around the picture tube). Since posistor can’t be checked using multimeter I had to direct replace it and retest. I bought the part from electronics shop.

 crt tv posistor

Once the posistor was replaced and the TV was turned On, the color patches were gone.

 crttvrepair

Note: Assuming after the replacement of the posistor with the same symptom, this means the CRT tube itself have problem. If you have the degausser/demagnetizer, it would be much easier to diagnose this kind of fault. If you have degaussed the CRT tube and the problem still persist this means the CRT TV tube have problem and need replacement.

This article was prepared for you by Yogesh Panchal who works as a Computer Hardware Engineer in Mumbai India.

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Likes(317)Dislikes(15)

67 Comments

  1. Mervin

    October 21, 2014 at 6:43 pm

    Nice fix,you know things

    Likes(10)Dislikes(1)
    • Yogesh Panchal

      October 22, 2014 at 12:10 am

      Thanks mervin.

      Likes(6)Dislikes(2)
      • Amit Patel

        June 27, 2017 at 8:56 pm

        Thank very much..sir,

        Likes(0)Dislikes(1)
  2. biruk aweke

    October 21, 2014 at 6:57 pm

    hi yogesh panchal it is good solution but next time show type of tv if you can any way thanks for sharing.

    Likes(5)Dislikes(5)
    • Yogesh Panchal

      October 22, 2014 at 12:09 am

      sir thanks for comment,
      the TV i have repaired is originally SHARP TV but some one has replaced the original KIT with China make earlier and there is no identification for this china make kit .
      Thanks for comment.

      Likes(6)Dislikes(3)
  3. Waleed Rishmawi

    October 21, 2014 at 7:32 pm

    one way to test the PTC is once you have taken it off board, give a little shake and from experience, most of the bad ones usually make noise inside once they are shaken..

    Likes(19)Dislikes(2)
    • Yogesh Panchal

      October 22, 2014 at 12:06 am

      You are right waleed , same i have missed to make a note in the article when i removed PTC while i have shake it i hared noise like some thing is broken in side. thanks.

      Likes(6)Dislikes(0)
      • Vishwa

        May 6, 2016 at 8:46 am

        Hi Yogesh,
        Please guide me how can I buy a posistor online in india. I need a 3 pin posistor ( MZ73B 18ROM )

        Thanks

        Likes(3)Dislikes(1)
  4. moshe

    October 21, 2014 at 7:42 pm

    great to know!!
    thanks

    Likes(0)Dislikes(0)
    • Yogesh Panchal

      October 22, 2014 at 12:11 am

      thanks sir

      Likes(1)Dislikes(0)
  5. Rudi Wijaya

    October 21, 2014 at 7:44 pm

    Great repair mr.yogesh! Thanks!

    Likes(0)Dislikes(2)
    • Yogesh Panchal

      October 22, 2014 at 12:11 am

      thanks Rudi

      Likes(0)Dislikes(0)
  6. mosbad

    October 21, 2014 at 7:52 pm

    Good job, good technique and approach

    Likes(0)Dislikes(1)
    • Yogesh Panchal

      October 22, 2014 at 12:13 am

      thank you sir.

      Likes(0)Dislikes(2)
  7. Vasile Petrica

    October 21, 2014 at 8:05 pm

    Very interesting these TV problem!Bravo,congratulations!

    Likes(0)Dislikes(3)
    • Yogesh Panchal

      October 22, 2014 at 12:12 am

      thank you sir.

      Likes(0)Dislikes(1)
  8. Robert

    October 22, 2014 at 12:14 am

    Good job Yogesh. Thanks for the article.

    Likes(0)Dislikes(0)
    • Yogesh Panchal

      October 23, 2014 at 5:24 pm

      Thank you sir.

      Likes(0)Dislikes(0)
  9. Joshua oloo

    October 22, 2014 at 12:27 am

    Thanks Mr.Yogesh for the Article.I've once encounted such problem and its common with LG Tv 21'' colour Crt.normally caused by magnatic fields from stereo speakers.Regards!!

    Likes(7)Dislikes(0)
    • Yogesh Panchal

      October 23, 2014 at 5:24 pm

      Sir, Thanks for comment.

      Likes(1)Dislikes(0)
  10. Humberto

    October 22, 2014 at 12:43 am

    Great repair Yogesh Panchal, congratulations

    Likes(2)Dislikes(0)
    • Yogesh Panchal

      October 23, 2014 at 5:25 pm

      Thanks Humberto

      Likes(1)Dislikes(1)
  11. Luciano

    October 22, 2014 at 1:48 am

    Hi Yogesh,
    Thanks for the article.

    Likes(1)Dislikes(0)
    • Yogesh Panchal

      October 23, 2014 at 5:25 pm

      You are welcome

      Likes(0)Dislikes(0)
  12. Lloyd Bond

    October 22, 2014 at 5:34 am

    good info to have.

    Likes(0)Dislikes(0)
    • Yogesh Panchal

      October 23, 2014 at 5:26 pm

      thank you sir

      Likes(0)Dislikes(0)
  13. beh

    October 22, 2014 at 2:07 pm

    YOGESH: thanks for sharing your experience .

    Likes(3)Dislikes(1)
    • Yogesh Panchal

      October 23, 2014 at 5:26 pm

      Thanks Beh.

      Likes(3)Dislikes(0)
  14. l.boopathiraj

    October 22, 2014 at 4:46 pm

    good job yes this type of problems i attend when i was worked B P L as service engineer in year 2001 ..PTC problem and degaussing coil problem man mad problem like childrens played with magnet near tv some color patches appear on screen
    this type problem curing by external degaussing coil

    Likes(4)Dislikes(0)
    • Yogesh Panchal

      October 23, 2014 at 5:27 pm

      sir thanks for comment.

      Likes(0)Dislikes(1)
  15. freeman

    October 22, 2014 at 5:39 pm

    That positron is a ptc that is a positive temperature coeficient thermister!
    Of course they can be tested! they show a very low resistance if they aregood when cold, As the current rushes into the degausing coils the thermister heats up and presents a virtual open circuit to the coils thereby blocking the current flow. The other thing is that the tube canot be the fault in this situation. The colour patches exist so the guns are firing correctly only there is a stray magnetic field influence on the tube. At startup, the influence is natural due to surrounding metal parts and is eliminated by the alternating magnetic degauss field,which is produced for a couple of seconds.

    Likes(5)Dislikes(0)
    • Osman Alsinnary

      October 23, 2014 at 2:37 am

      Good Job & Good repair Article
      Thanks YOGESH ...

      Likes(0)Dislikes(0)
    • Yogesh Panchal

      October 23, 2014 at 5:28 pm

      Sir Thanks for your comment.

      Likes(0)Dislikes(1)
    • Yogesh Panchal

      October 23, 2014 at 5:30 pm

      Sir, Thanks for comment.

      Likes(0)Dislikes(1)
  16. David kirima

    October 22, 2014 at 9:57 pm

    i learn alot from your teaching eg crt color patches problems solving. thanks alot.

    Likes(0)Dislikes(0)
    • Yogesh Panchal

      October 23, 2014 at 5:29 pm

      your welcome.

      Likes(0)Dislikes(0)
  17. Abdul Haleem

    October 22, 2014 at 11:09 pm

    This kind of problem occurs when the metal mesh,shadow mask just behind TV screen becomes magnetized due to strong magnetic fields generated near the TV screen like keeping strong magnets, operating electric motors (vacuum machines), keeping hi-fi speaker system near the screen and also moving the TV to another place especially when TV screen faces earth's north pole while carrying it all have influence in causing colour patches on the screen. Keeping the TV on stand-by mode and using it without switching off main power too causes in the long run colour pathces. In this case removing power to the TV and keeping it off for about 30 minutes to allow PTC to cool down and switching the TV on again solves the problems if in-built degaussing circuitry is ok. But it's a good idea to use external degaussing coil to demagnetize the screen periodically.

    Likes(6)Dislikes(0)
    • Yogesh Panchal

      October 23, 2014 at 5:29 pm

      Sir, Thanks for comment.

      Likes(0)Dislikes(1)
      • Abdul Haleem

        October 25, 2014 at 10:46 pm

        You are welcome Mr. Yogesh. I'm from your neighbour country, Sri Lanka

        Likes(2)Dislikes(0)
        • Yogesh Panchal

          October 27, 2014 at 3:13 pm

          Dear Abdul Saab,

          world is become narrow thanks to the All technology inventors for giving us possibilities to share and communicate to help each other thanks again.

          Likes(0)Dislikes(0)
  18. James

    October 25, 2014 at 3:46 pm

    Hi Yogesh I have a Philips Tv case with me serial Product no. 14PT1482/50T

    This tv turns on normally and shows normal but suddenly after some minutes the screen starts to brighten itself till it bleaches out completely to pure white with horizontal lines across the screen...pls can you help direct me with a working solution or fix thanks in advance will be posting the result here as feedback thanks for your help once again

    Likes(0)Dislikes(0)
    • Yogesh Panchal

      October 25, 2014 at 11:33 pm

      Dear James,
      Do you have any repair experience??? Because this Type of TV have some high voltages in side it will harm you badly so if you.as per your description You have to check +B supply if it is OK around 110V DC then check then EHT ( Screen Voltage adjust) and surrounding components.

      Likes(1)Dislikes(0)
      • james

        October 29, 2014 at 4:20 pm

        Yeah I have some electronics repair experience only that I'm just starting out and need some helps from experts like you till I become an expert myself. thanks for the tips

        Likes(0)Dislikes(0)
  19. Abdul Haleem

    October 25, 2014 at 10:43 pm

    Hi James,
    It seems your TV has retrace lines problem. To explain it technically this space is not enough. Pls. check or replace resistors(in kilo Ohms) connected in series with each cathode on the CRT board also check other high value resistors there. Directly replace B+ capacitor that feeds B+ pin of the Fly-back transformer. And also replace other caps that have value of 160V/22, 33, 47 or 100µF in B+ track from SMPS to FBT. Check other e-caps in G1 and G2 circuit. Finally re-solder CRT board, FBT and power supply area on the PCB.

    Likes(3)Dislikes(0)
    • james

      October 29, 2014 at 4:27 pm

      hi Abdul Haleem thanks for the more elaborate expert tips you gave I very much appreciate your help am on the TV repair work right now just in time to receive the tips you guys sent me thanks.

      Likes(2)Dislikes(0)
  20. Tushar Shah

    October 27, 2014 at 1:07 am

    Dear Mr. PAnchal,
    I have PANASONIC QUINTRIX F 34 inch CRT TV and it has Green & White colour patched all over the screen when I switch on the TV & after couple of seconds it goes away & my screen become blank.
    Could you please guide me what will be the problem OR would you be able to repair it ?
    I am also from Mumbai & from KAndivali - Dahanukar Wadi Area.
    Hoping to listen from you soon.
    Thanks.
    Tushar Shah

    Likes(1)Dislikes(0)
    • Yogesh Panchal

      October 27, 2014 at 3:03 pm

      Dear Tushar ,
      I am staying in Dahisar (East),I have to take permission from jestin sir before i disclose my contact information ; any way are you able to troubleshoot your own ?? If you are familiar with electronics repairing just provide more detail are you able to see any TV program through cable connection and picture is visible with the color patches ??

      Likes(2)Dislikes(0)
  21. reza

    October 29, 2014 at 8:23 pm

    hi
    thank at all repairmans.

    Likes(2)Dislikes(0)
  22. Jasim

    November 23, 2014 at 5:38 pm

    thanks indeed for fault clarification. your article appreciated. keep it up

    Likes(0)Dislikes(1)
  23. Blessed

    June 13, 2015 at 7:54 am

    Please no raster and no picture i have change the line transformer oscilating to the sreen but still d same

    Likes(0)Dislikes(0)
  24. Sanjeev

    July 11, 2015 at 8:09 pm

    Dear Mr Yohesh
    My Samsung CRT TV was having colour problem
    . its posister was damaged. I just removed broken insulator from it and switched on the TV. Within no time degaussing coil burnt and the mains fuse blew off protecting major damage . thereafter I removed connections of degaussing coil and TV is running now . how do I repair it now

    Likes(0)Dislikes(0)
  25. Eugene Murray

    December 7, 2015 at 8:43 pm

    I have a 29 inch Philips TV. PT2420 model, the horizontal width is less, hence black bars, right and left side of picture. How do i adjust this so as to get full screen.

    Likes(0)Dislikes(0)
    • Jestine Yong

      December 9, 2015 at 8:17 am

      HI Eugene,

      If it can't be adjusted from the remote then probably the pincushion circuit could have problem. A less B+ supply voltage also can cause such problem. Check on the B+ supply first and if normal then check on the pincushion circuit.

      Jestine

      Likes(1)Dislikes(0)
  26. Niyas

    December 25, 2015 at 9:26 pm

    Thank you Sir

    Likes(0)Dislikes(0)
  27. NTIRENGANYA Desire

    January 13, 2016 at 7:41 pm

    Dear Sir,
    I stay in Rwanda/kigali, I am a new repairer of tv, a client brings me a tv which displays images in much green color, what problem should it have and can you assist me in how to repair it?
    Waiting for your kind assistance, I thank you.

    Likes(0)Dislikes(0)
    • Jestine Yong

      January 14, 2016 at 9:39 pm

      Hi Ntirenganya,

      Try check out the link below and related article:

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

      Jestine

      Likes(1)Dislikes(0)
  28. a.srikanth

    March 7, 2016 at 4:12 pm

    thanks for your advice and giving knowledge internal parts in crt tv

    Likes(0)Dislikes(0)
  29. vijay kurhe

    November 1, 2016 at 7:45 pm

    Sir. My tv some time yellow colour. and some time good see.what i can do.plz give me advice. Onida 4table colour tv.

    Likes(0)Dislikes(0)
    • Jestine Yong

      November 2, 2016 at 12:31 pm

      Hi Vijay,

      Check for dry joints in your crt tv board.

      Jestine

      Likes(0)Dislikes(0)
  30. Brian

    March 12, 2017 at 12:34 pm

    Good day sir

    My LG flatron tv's picture is curved on the side instead of being straight and it's getting smaller. Can you please assist me on how I fix it?

    Thanks

    Likes(0)Dislikes(0)
    • Jestine Yong

      March 13, 2017 at 8:10 pm

      Hi Brian,

      Make sure the B+ voltage is good. If it is good then check for bad modulation diode and the pincushion transistor.

      Jestine

      Likes(0)Dislikes(0)
  31. Andy

    June 24, 2017 at 1:41 am

    Thanks I changed the posistor and the rainbow colors disappeared and the my 21"LG CRT TV is now back to normal.

    Likes(0)Dislikes(0)
  32. TITUS JOHN DANDA

    August 27, 2017 at 5:48 pm

    i have a HITACHI C21-SF980 MODEL,IT HAS THE PROBLEM OF REDUCING ITS SCreen size right and left of the screen,about 5mins after being swithed on.and also the colour becomes blury.What might be the problem?

    Likes(0)Dislikes(0)
  33. AMANDA SOREL

    April 22, 2018 at 1:03 pm

    Mr. Yong, I dropped my crt tv.
    On the right of the screen is red, and green circles. The rest of the picture is good. The colors are bright and trigger my migrains. Can I fix it?

    Likes(0)Dislikes(0)
    • Jestine Yong

      April 23, 2018 at 7:38 am

      Hi Amanda,

      I'm afraid the internal shadow mask already collapsed causing the color spot and thus it can't be repaired. Before that you can try to demagnetize it using a demagnetizer and iif it can't cure the problem then is the CRT tube problem.

      Jestine

      Likes(0)Dislikes(0)
  34. Nkokana

    October 31, 2019 at 7:26 pm

    Hey Mr Justin. I am repairing a Chinese crt TV 54cm that keeps blowing a vertical ic. B+ voltage is 115v and voltage to the ic is 32 which is 78141.no triac to reduce voltage

    Likes(0)Dislikes(0)
    • Jestine Yong

      November 4, 2019 at 8:38 pm

      Hi Nkokana,

      There are few possibilities such as bad quality of vertical ic used, shorted vertical winding and bad components in the vertical ic corresponding circuit.

      Jestine

      Likes(0)Dislikes(0)

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