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The Unfinished Repaired Work

By on April 9, 2022
The Unfinished Repaired Work

 

 

 

 

 

 

 

This CRT TV was brought to me by an elderly widow with complaint of not switching on. When I checked it, I noticed the ac cord had burnt at base of cover case. See cover.

HOW TO REPAIR A BROKEN CRT TV

I replaced ac cord and powered tv, tv powered on and see what appeared on screen below:
one horizontal line tv
 
 
As you can see, it’s a horizontal line. With this I know the  problem has to do with vertical circuit. So I removed case cover, clean board and perform visual checking, nothing suspicious. Then decided to do voltage test on the vertical IC pins,(No utc78040).
 
 
This IC has 7pins and one of it’s pins  was having 0 voltage, so I suspect this IC. I then trace the track of this pin to a diode which was opened (1N4004).
 
OPEN 1N4004 DIODE
 
 
Then I decided to check all components in vertical circuit in which I discovered some e – caps that are high in ESR values, tank e-cap had oxidized, see pictures below:
 
OXIDISED CAP
 
 
Then I try to remove IC by desoldering it out, but I got some track damaged as result of lack of experience ( doing this 1st time anyway).
 
DAMAGED CIRCUIT TRACK
 
So I replaced IC with LA78040, diode with 1N4007 and also other bad components, also repair damaged tracks pictures below:
 
FIXING BROKEN CIRCUIT TRACK
 
HOW TO FIX CRT TV
 
HOW TO FIX A BROKEN CRT TV
 
 
Then connect everything together and power on TV.
 
 
The video and audio came up load, but picture is blur!!.What a disappointment!!.
 
BLUR PICTURE IN CRT TV
 
TV BLUR PROBLEM
 
 
So I suspected problem could be with either FBT or crt socket, I check on socket, it’s o.k. In my country, brand new fbt is not available, except those extracted from junk boards which I do not intend to use because it will not last. So the only  option I have is to order it online.
 


 
So I  inform my customer about this and she said she can’t afford the cost and moreover the TV is old fashioned. I was so much disappointed and felt bad I could not finish this repair work. This time “it’s the unfinished repaired work “.
 
imoudou onwuwah

This article was prepared for you by Imoudu Onwumah from Nigeria. He is 62 years old and has just 3 years experience in electronics repairs. I started career in hotel industry as a chef, but then I was doing repairs only in electrical repairs as a hobbyist. In 2018, I decided to learn about electronics which through Jestine’s electronics e-books and holding my hand, am an electronics techie today.

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Note: You can read his previous article on Happy New Year Broken Down Audio Amplifier Restored Back to Life

 
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9 Comments

  1. Parasuraman S

    April 9, 2022 at 10:51 am

    Do recharge of the CRT Tube and remove the internal shorts. Replace all electrolytic caps on the board. Retouch all soldering joints from one end to the other, without leaving any points. The TV will certainly come back to its glory!

    Likes(9)Dislikes(0)
  2. Albert van Bemmelen

    April 9, 2022 at 2:35 pm

    Working on old TV sets and other old defect devices is always a risk we dare to take without knowing if we do succeed! Maybe you still can fix the set with Parasuraman's tips? A bit odd that they named this old TV a DIGITAL TV?
    Although I still wouldn't know how to remove internal shorts in a CRT Tube or how to recharge it. I have never done this and probably never will, since these TV sets are almost completely gone now.

    Likes(2)Dislikes(0)
  3. Waleed Rishmawi

    April 9, 2022 at 3:37 pm

    do not feel discouraged my friend you did what you can to get it fixed. keep up the good work. have you tried to adjust the focus on the FBT? I am sure you already know there is a knob for brightness and one for focus. have a blessed day

    Likes(6)Dislikes(0)
  4. Imoudu Onwumah

    April 9, 2022 at 4:13 pm

    Mr Parasuraman
    Thanks for your advice,I do appreciate.

    Likes(1)Dislikes(0)
  5. Yogesh Panchal

    April 9, 2022 at 11:58 pm

    Imoudu Onwumah,

    In this case as per your assumption cause for this fault is FBT or CRT Base is right & guide line of Mr.Parsuraman also do help. some time testing CRT Base with multimeter seems OK but it does not fit properly or may be pins of CRT is oxidized did you try to Clean it up using Petrol??.......Peel off traces are common problem due to over heating by soldering Iron. Always use solder bridge technic for removing 8 pin IC & you have to keep good Magnifier Glass for reconfirming the trace repair work. do not use open wire for jumper some time it will mess-up the time and money you spent for fixing the device.Never give up if you tired in troubleshooting put the work on hold and start troubleshooting when you are in fresh mood may be on next day......All the best..

    Likes(4)Dislikes(0)
    • Parasuraman Subramanian

      April 10, 2022 at 12:35 pm

      Very good practical suggestion!

      Likes(0)Dislikes(0)
  6. Imoudu Onwumah

    April 10, 2022 at 5:35 am

    Mr Albert
    Thanks for your comments.In my country we still have some folks who still use this crt tv,just because they can't afford cost of led tv. Techies have to help them out.One old folk ask me one day if l could help her get small led tv at about 4 us dollars.I laughed.

    Likes(1)Dislikes(0)
  7. Imoudu Onwumah

    April 10, 2022 at 5:41 am

    Mr Waleed
    Thanks for your comments and encouragement.l have tried to adjust focus knob.have a nice day.

    Likes(0)Dislikes(0)
  8. Imoudu Onwumah

    April 11, 2022 at 5:35 am

    Mr Yogesh
    Thanks for your suggestions,I will apply them in practical.Have a nice day.

    Likes(0)Dislikes(0)

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