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LG LCD TV Repaired

By Jestine Yong on March 3, 2015

This LCD TV was brought dead by my friend. It was lying neglected in his house for a very long time and my friend asked me to check whether something can be done to revive it.

On opening the back cover, I saw cobwebs and full of dust. Cleaned it thoroughly. Noticed that 68mfd/450 Cap had bulged and fuse was blown. Removed the PS board, replaced both the 68mfd/450V caps. Checked ESR of all other electrolytic caps. Since many of them were out of range, decided to replace all of them. Connected a 100W bulb across the fuse and switched on PS board. Outputs were perfectly 5.1 and 15V respectively.

Checked the Mother Board for any visible damages. Could not find any. Connected the PS. Display came on, but got off and on again. Though I knew it could be due to the load of the Bulb, I tried putting a 40W bulb, with the same result. Later on Jestine Yong confirmed it could be due to the bulb drawing current, which makes the capacitors charge and discharge. So, placed 3.15A fuse its place. The display came on. But there were disturbing lines across the whole screen. OSD menu is good this means the LCD panel is not the cause of the problem. See the photo below:

Since the TV came back to life, I was very happy and decided to do a thorough job. So, I removed the MB and PS once again. Did a thorough dry solder patch up. Replaced all the electrolytic caps in MB, as most of them were out of ESR range, including the SMD caps.

Removing SMD caps were very easy, when I followed the guidelines given in the following link (not even one cap tore the track!): https://www.youtube.com/watch?v=Y1l7qSezFDQ I soldered the new ordinary caps, by cutting its leads to small size, and placing it on top of the left over leads of the SMD caps, which made a firm bond.

But through hole caps gave me a tough time.But this tool was very handy:

Cleaned the board thoroughly using isopropyl alcohol, taking care that it does not peep into windings of any coil such as SMPS transformers, backlight transformers etc. If it goes in, it will remove the varnish coating of the wire and cause shorts.

Here is a snap of all the caps replaced:

All work done satisfactorily and the boards are put back to its place, after lubricating every connector with Philips Switch Cleaning Oil, using an injection syringe.

A job well done and tasks accomplished! Here is the final result: (Though there are a few patches on the top and bottom, [marked with arrows in the picture] probably due to children playing with it, the picture is good and the LCD panel might have some more life!)

This article was prepared for you by Parasuraman Subramanian from India. He is 65 years old and has more than 30 years’ experience in handling antiques equipment Valve Radio, Amps, Reel Tape Recorders and currently studying latest techs classes conduct by Kerala State Electronics Technicians’ Association. He was a BBA graduate, retired as MD of a USA company and presently working as Consultant Manager, Purchase & IT, in Irinjalakuda Cooperative Hospital.

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lcd tv repaired

29 Comments

Merlin Marquardt

March 3, 2015 at 10:03 pm

Very good work! Very hard work! Well done!

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Mohammed Kasim

March 3, 2015 at 10:53 pm

Good article. I am from lakshadweep,India. Which are the connectors u lubricated. From where(kerala) I will get Philips oil

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Yogesh Panchal

March 3, 2015 at 10:56 pm

Good job Sir,

I think for Removing SMD caps safest way is either use chip quik or hot air rework because pulling out components from PCB will make your job wrost some time by damaging trace.

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- Robert Calk
  
  March 8, 2015 at 8:06 pm
  
  Hi Yogesh,
  
  I use my Hot Air Rework Station also to remove SMD components. Many people think you should use the lowest heat possible to remove components, but I have found that not to be the case. I use about 400oC with the air low so it won't blow the components all over the place. That will heat and loosen the component contacts faster so not to heat up the PCB and component itself as much. Lower heat takes longer to melt the solder thus transferring more heat to the PCB and component.
  Have you found that to be the case also?
  
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Humberto

March 3, 2015 at 11:40 pm

Hi Mr. Parasuraman Subramanian, good job and good idea using isopropyl alcohol for cleaning the board. Congratulations

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john

March 4, 2015 at 12:15 am

Excellent post. Was wanting to repair Iphones , However I understand the parts are to expensive. What do you think?

John

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- Robert Calk
  
  March 8, 2015 at 8:12 pm
  
  Hi John,
  
  I know a guy that owns his own repair shop and much of his business right now is repairing IPhones. Of course, most of the repairs are replacing broken screens and stuff, but he can do much more than that.
  
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t-ramadoss

March 4, 2015 at 1:16 am

electronic service has no age limit--very good work -- thank you sir--

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Jignesh

March 4, 2015 at 2:54 am

Hello,

I have with me Samsung LE32A336J1D. It was working perfet up till now.

Just before few days when I switched on the TV, just after 5 seconds screen turned white with very faint image in background.

Can any one throw light on this?

This TV has served me well and I just don't want to discard it as I strongly believe that there could be very minor problem.

May I request any one of you to throw light and help me considering my knowledge of electronics is basic.

Thanks,

Regards,

Jignesh.

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- Robert Calk
  
  March 4, 2015 at 11:27 am
  
  Hi Jignesh,
  
  Did you check the pico fuse on the T-Con board to see if it open?
  
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- Parasuraman S
  
  March 4, 2015 at 2:20 pm
  
  Since the display is coming on, the PS could be ok. But make sure that PS outputs are exactly as marked near he connector and are ripple free using an oscilloscope. Secondly remove the connector from the MB to the panel, clean it with pencil rubber, and put it back. Look for any dry joints in PS and MB. Look for any secondary regulator ICs in the MB getting over heated. Check its output voltages for accuracy.
  
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  Reply
  - Jignesh
    
    March 6, 2015 at 6:39 am
    
    Thanks for your reply.
    
    So far I have done two things. 1. Checked output voltages on all pins and it is correct. 2. Four ribbon connectors cleared as below.
    - Both sides of connectors from MB to T con
    - T con board to screen two connectors.
    
    But there is no change. 2-5 second normal screen after that dark pink and finally complete white with very faint image in background.
    
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    Reply
    - Robert Calk
      
      March 6, 2015 at 4:10 pm
      
      If you buy Mr. Kent Liew's V3.0 & V4.0 e-books, I am very confidant that you will find the culprit. Or you could try new LVDS cables or try a new T-Con board and see if it fixes it.
      
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      - Jignesh
        
        March 7, 2015 at 5:11 am
        
        Thanks.
        
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        Reply
      - Jignesh
        
        March 31, 2015 at 5:22 am
        
        Thanks to all experts for their guidance. I have replaced power supply board and t-con board AND tv is up and running just as it was working earlier.
        
        A Big Thank You to all of you.
        
        Regards.
        
        Jignesh.
        
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        Reply
        
        Jestine Yong
        
        March 31, 2015 at 6:52 am
        
        HI Jignesh,
        
        Congratulation!
        
        Jestine
        
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        Reply
    - Parasuraman S
      
      March 6, 2015 at 10:08 pm
      
      Kindly confirm whether you have checked the voltages of secondary voltage regulator ICS, generally located near the connector that goes to the T-Con board. If any of the transistors are getting more voltage than it should, this kind of shutting of the display can happen. Did you check over heating of any of the components either in T-con or the circuitry immediately before it?
      
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      - Jignesh
        
        March 7, 2015 at 5:11 am
        
        Thanks.
        
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      - Amir Mukhtar
        
        March 7, 2015 at 5:21 am
        
        Goog Job Mr. Parasuraman Subramanian
        
        thanks you
        Amir Mukhtar AShrafi
        
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Anthony

March 4, 2015 at 11:44 am

Great job and another device which does not go to landfill and that helps the environment! Congratulations !

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L.BOOPATHIRAJ

March 4, 2015 at 11:48 am

GOOD IDEA SUPER

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Ehsan Murad

March 4, 2015 at 11:56 am

Dear PS,
Nice write up.Can you shed some more light/pics of cleaners/lubricants you use.And I understand the tool you use is a 2in1 soldering iron+pump?
Thanks again
Ehsan

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ebneila

March 4, 2015 at 12:29 pm

I have worked in electronics well over 50 years and have found some very stubborn problems. One that almost added to my already grey hair was intermittent audio drop out on a Sony SLV-R1000 VCR. Regardless of how many components I checked nothing accounted for reduced 5 volt supply. Not having a schematic didn't help either. Bottom line: the problem was tracked to a tiny carbon path between two 5 volt sub regulator leads. Sometimes inspecting with a good magnifier will reveal much

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Mohamed Sittiq M

March 4, 2015 at 12:29 pm

Dear Sir,
thanks for information. superb....
mohamed Sittiq M

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ebneila

March 4, 2015 at 12:39 pm

Every tech has favorite methods and cures. I've found Ketone or Acetone in very good for cleaning intricate PCBs of dust, mildew and rosin contaminants. Alcohol evaporation can draw moisture and shorting problems especially in transformers and microprocessor pins. Use a clean tooth brush for this application

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Parasuraman S

March 4, 2015 at 2:14 pm

Many thanks for all your supporting responses. Let me reply to all comments/doubts:
1. I have Philips switch cleaning oil in stock (bought several years ago, now no longer available).
2. All connectors which has pins and sockets (male and female). I use syringe to inject a drop in each socket ensuring no spill overs. This cleans, clears corrosion and greenish fungi, and enables better contact.
3. No idea about iphones, too tiny for my eye sight.
4. It is a manual desoldering iron, bought for Rs.600 from Vishal Electronics, Sadar Patrappa Road, Bangalore. Very good one. But be careful with its tips. Very brittle!

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Amir Mukhtar

March 7, 2015 at 5:22 am

Thank you Parasuraman Subramanian for sharing nice article to Learn Students and Technicals.

Keep Sharing your Expertise

Regards
Amir Mukhtar ashrafi

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dicksy

March 9, 2015 at 5:12 pm

good job n nice article.thanx

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Isaac

April 8, 2015 at 7:55 pm

my Samsung monitor displays white when I on it and I replaced 470/25v and now power comes on the board but no display.
please help me what should I do?

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