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LG LCD TV Repaired
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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