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How To Repair LED TV Mainboard
This LG LED 24 Inch TV came in for repair with the complaint of no power. For this model, it did not use the switch mode power supply board and in fact it uses an external power adapter that was rated 19 volt -1.6 Amp. You can check out the two photos below:
For a no power symptom TV, the first thing to do is to check the output dc voltage from the external power adapter. If there is no output voltage then the power adapter is at fault.
In this case, the power adapter was checked to be good and it measured 19.11 Vdc-see the photo below:
Since the power adapter was working fine this means I have to open the TV cover and check on the mainboard. The photo below is the LED TV mainboard:
Usually for this kind of problem I will start to check from the Power Jack area first. I checked on the protection SMD resistor (R100=10 Ohm) and it was open circuited. This component acted like a fuse and will open circuit when there is a over current drawn.
Once this protection resistor was open circuited, we have to find out what causes the problem. After checking on the few components nearby I confirmed that only one Power FET was shorted.
I soldered out the two components and put the replacement parts. For the power FET I got it from another TV junkboard.
After fixing the two components and powered On, the TV came back to life. I was very happy because there was no other bad components. Another job done and earn some profits.
Conclusion- Don’t immediately repair the TV mainboard or any other mainboards unless you have carefully studied how the mainboard works. Otherwise you will be shooting in the dark as where to start to check and this will cause your time lost. If you want to be excel in LCD/LED TV repair you can check out on Kent’s and Damon’s ebooks.
This article was prepared for you by Suranga Bandara who owns an Electronics repair shop in Anuradapura, Sri Lanka.
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