Shorted SMD Transistor In LED TV
The complaint of this 23″ LED TV was no display but there was power (the power LED light was on). The sound was good too except no display. However, the TV LED backlights were On -see the photo below.
This means that the internal LED TV driver board was working fine.
Once the cover was removed, I could see only two circuit boards i.e the main board and the backlight LED driver board.
I then checked on the mainboard voltages to the LED Backlight driver board and found that the three dc voltages of 3.3 volt, 5 volt and 12 volt were present. You need to check these pins when the dc power jack is connected and is on.
Next, I checked on the 5 volt dc line to the TV panel and found that it was only 1.44 volt instead of 5 volt. I knew this is the main cause of the TV no display problem.
I started to track from this 5 volt connector pin and found one suspicious SMD transistor where it received 5 volt but the output was only 1.44 volt.
I soldered out the SMD transistor and check it off board and true enough the transistor had a shorted leads where it showed 17 ohms. The ohms value should be high.
It is time to look for the spare part. I search from the junk board and found the right SMD transistor and soldered it-see the photos below:
After putting in the good SMD transistor and powered On, the 5 volt came back.
You can see the 5.09 volt reading from the meter in the photo below:
The best moment was able to see the TV display came back and the satisfaction is beyond description.
Conclusion- It is possible to repair TV mainboard if you able to track or understand the circuit. If you wish to become a better TV repairer you can check out 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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Robert Calk
May 5, 2018 at 12:48 pm
Good job, Suranga.
Suranga Electronics
May 5, 2018 at 11:21 pm
Thanks Mr.Robert
Parasuraman
May 5, 2018 at 1:36 pm
Very professional approach. Exposes your depth of knowledge! Thanks for sharing!
Suranga Electronics
May 5, 2018 at 11:20 pm
Thanks Mr parasuraman
Sudh
May 17, 2021 at 12:05 am
Specifications of that transistor for my 32 inch LED tv ?
Muhammad Irfan
May 5, 2018 at 5:39 pm
how did you come to know that you found the same transistor from junk board? Because you didn't shared transistor code.
Henrique Jorge Guimarães Ulbrich
May 5, 2018 at 7:28 pm
Very good (and fast), Suranga. Thanks for new knowledge. Just a doubt: The power supply board was not visible.
Albert van Bemmelen
May 5, 2018 at 7:41 pm
Nice work! Question remains what caused it. And that it is not a bad design failure that repeats itself.
Chigado
May 5, 2018 at 10:17 pm
good illustration for beginners.Thanks
Steve
May 6, 2018 at 2:21 am
Sweet nice job
Andrew F. Ali
May 6, 2018 at 6:27 pm
Good job, once again Suranga.
Yogesh Panchal
May 6, 2018 at 11:43 pm
Good Job!Suranga
Chaminda Jayarathne
May 8, 2018 at 5:20 pm
Greet Job Suranga & Thanks to sharing.
Justice
May 9, 2018 at 1:14 pm
Interesting article. You mention 3.3 ;5 and 12 volts from mainboard quite informative,Thanks Suranga.
Carlo Alberto Birocco
May 10, 2018 at 4:38 am
Smart approach to fix the problem. Well done! Thanks for sharing, bro.
Tito Kanshulu
May 10, 2018 at 5:06 pm
Nice work Suranga and thanks for sharing
Kirwa Boaz
May 16, 2018 at 9:18 pm
I have a 32" super slim Lg TV that powers on displays perfectly but after sometime it displays horizontal black lines at the center of the screen and still works well. What might be the problem
JAMES
September 6, 2018 at 2:13 am
WHAT WAS THE NUMBER ON THE SHORTED TRANSISTOR
Ulises Aguilar Pazzani
September 13, 2018 at 11:04 am
good after noon , but grate Job Sir
Jose Asinero
October 28, 2019 at 12:16 am
Hello sir.. Thank you so much for this very genius idea. I tried it.. I even did not test the transistor from my spare monitor.. I just got it and solder it to my led tv. It realy fix my tv now... Thank you so much...
jimmy
February 6, 2020 at 5:09 am
Hi I want to identify the Zener diode located to d811, I am trying to fix a tv mainboard here and there is one blown. Can you help me please. This is the exact same I need
Thank you
Jimmy
Ivan
May 3, 2020 at 2:44 am
thanks sir, lesson grasped
Raz Khan
May 27, 2021 at 11:31 am
I just wanted to leave a comment behind to support you. Thank you for this short and simple explanation of something a-lot of people would stay far away from because they believe its way far from there comprehension.
I hope you all the best for the future my Friend.
Raz