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Video Missing In Samsung CRT Solved

By Jestine Yong on June 27, 2020

Model and make : Samsung CB20-F4 CRT TV

Problem reported: No video, audio ok. (Black screen).

Checking at workshop: Problem confirmed.

Trouble shooting and rectification done: Retouched uController IC and Chroma Processor IC and a few other places wherever it was found. Power supply was not stable. Traced it to 120K Resistor in SMPS. Replaced it along with a couple of high voltage capacitors. As Horizontal Oscillation was taking place and all other voltages on the board are ok, suspected the TV Processor IC. Replaced it. Video came on with blur raster. Checked the Focus Voltage Wire inside the CRT Socket and found it to be worn out due to fungus attack. Cut the tip and made a fresh exposed contact and soldered it. Also replaced screen voltage filter capacitor as a routine preventive maintenance. Saw the menu was not clear enough and looked like the settings got affected, indicating a software corruption in memory IC. So replaced it with a blank memory IC. Switched on the set and allowed the program to do the auto copying to the blank IC.

Result: Fed Video and found it to be working very well. Mission accomplished, adding one more satisfaction to the collection bag.

Here are the pictures:

This article was prepared for you by Parasuraman Subramanian from India. He is 70 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.

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You may check on his previous repair article below:

https://jestineyong.com/shorted-transistors-and-blown-fuses-found-in-akai-tuner-receiver/

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Television repair

15 Comments

Subhash.p

June 29, 2020 at 8:55 pm

Good article. .
Congratulations to parasuraman sir.

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- Parasuraman S
  
  June 30, 2020 at 6:46 am
  
  Many thanks!
  
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Albert van Bemmelen

June 29, 2020 at 9:14 pm

No matter how many failures those heavily failing crt TVs have you still manage to fix even the worst cases! From good experience you immediately know how to tackle any of those problems you face. And although I know that you have an oscilloscope you hardly ever need it. Which is admirable! Thanks for sharing!

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- Parasuraman S
  
  June 30, 2020 at 6:47 am
  
  Many thanks for your encouragement. I am grateful to my techie friends who are ready to help and guide!
  
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Waleed Rishmawi

June 29, 2020 at 10:40 pm

Very tough case but you handled it well as expected. A pro in action. Good job my friend

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- Parasuraman S
  
  June 30, 2020 at 2:22 pm
  
  Many thanks, dear! Good encouragement and I love it!
  
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Humberto

June 30, 2020 at 11:16 am

Good repair and article too. Congrats.

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- Parasuraman S
  
  June 30, 2020 at 2:23 pm
  
  Many thanks! Your continued support really matters!
  
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Mark

June 30, 2020 at 7:48 pm

Once again, the master has created a successful repair from a complex diagnosis.
Well done Parasuraman!

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- Parasuraman S
  
  July 1, 2020 at 8:06 pm
  
  Many thanks for the lovely comments! It helps a lot!
  
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Gassan Ali

July 1, 2020 at 2:44 am

Nice job. I wish these TVs are sti.

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- Parasuraman S
  
  July 1, 2020 at 8:07 pm
  
  Many thanks for your support! May God bless you!
  
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Joven Urbano

July 3, 2020 at 1:41 am

I am a newbie in this field and I am learning a lot reading repair tips from experienced guys like you. I have some questions, though: since you have removed the original memory IC, from where did the blank memory IC got its source for copying program content during autocopy? Do all TVs have an autocopy feature? Please have me enlightened. Thanks!

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- Parasuraman S
  
  July 3, 2020 at 10:23 am
  
  All the user settings with the latest changes are stored in this external memory. The uController refers to this at the time of booting to pick-up these settings. At the time of boot up, if it is a blank memory, the uController loads the original settings. However, in some latest TVs like LCD/LED, which have android protocol, these memory ICs do hold its own factory loaded programs as an external support. So if we load a blank memory, TV would not work. Whenever a TV is switched off and on, the reset will take place in the uController, to start the program from the first. (If the reset voltage is not there, the uController will not be able to boot up. That's one way of checking, when a device using uController is dead!) Only if settings are changed by the user or by service mode, these are stored in this external memory, which get picked-up at the time of booting. Hope this clarifies your doubt.
  
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Raj

August 5, 2020 at 9:26 pm

Interesting.. Thanks

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