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LG Slim TV With One Horizontal Line Solved
The complaint of this LG slim TV was one horizontal line across the screen. The common faults are usually bad vertical output IC, improper DC supply voltage, open vertical yoke coil, missing vertical signal from the vertical oscillator IC and also bad or leaky components in the surrounding area.
As usual, one need to open up the back casing in order to check on the circuit board. I was little surprised when I saw the vertical output IC was cracked and burnt-see the photo below:
Once you see a cracked IC, the first thing you need to do is to locate the part that was broken off. The reason for it is to track down the IC part number and this can eliminate the time of searching for the right part number.
The part number was LA78141 and you can see the datasheet below:
Besides the burnt vertical output IC I also discovered two dead lizard-see the photo below. Probably these two lizards could have cause the vertical IC to blow.
I also noticed that the vertical output IC had some dry joints at the pins.
I continued to check on the corresponding components to make sure all the components are good.
I had this new IC LA78141 for replacement and of course I had to clean the circuit board first before installation of the IC.
Ok, now the board is clean and I can power up the TV to see if the problem solved.
Guess that the one horizontal line problem was solved but there was another problem which is color patches in the TV screen. From experience, this kind of problem can be caused by bad CRT Tube, open degaussing coil, bad posistor or dry joints in the posistor area.
I checked on the degaussing coil and it shows low ohms reading which was good and there was no dry joints in the posistor.
So I directly replaced the posistor and powered it On and guess what? The display was back to normal and two problems solved. If you want to learn CRT TV repair you can check on this ebook by Humphrey.
This article was prepared for you by Suranga Bandara who owns an Electronics shop in Anuradapura, Sri Lanka.
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