Never Saw TV LED Lights Like These
This TV was brought to my shop by a lady next door. It is an LG model and I really hate LG product. Very complicated and parts too expensive. I powered the set and the LED came on but the display was dark. In my mind, it was all about LED Lights being open but it was totally a different story. Take a look.
As always, some screws off the back and inside the TV was exposed. As you can see, the power board, logic board, T-con board and finally the LED driver board. My attention was focused on the LED driver board and the LED lights. It is the one with metal shield on it.
The first thing to do is to make sure all the voltages are getting to that board. Since the stand by light is on, the logic board is kind of on the side for now. Checked the voltages on the power board and it seems like everything is in order.
Took the metal shield off and I could see everything on that board. The main fuse was intact on this board and all voltages read normally on this board. If you look the two arrows on top, you will see the black and red wires there. These are the main two power lines to the LED lights. They were getting the right voltages there which were 12 DC on each side. If the board is getting the right voltages and the LED lights are not coming on, it means two things. Either one of the LED lights is open or the board is getting the voltage but not handling the voltage load caused by the LED light strips inside the panel. The only way to find out is to expose the LED light strips and check them out.
Check this out. I never saw LED lights like these. Usually, the LED light strips are stretched out across the TV but these one only to the side on the TV. There are 50 LED lights on each side. This was very interesting.
Recently I bought this LED light tester on my last visit to the USA. It tests all kind of LED lights and very easy to use. It has two probes, one black and one red (sorry not in the photo). It works on AC voltage and it has a display of how much DC voltage is being used when testing the LED light. You can check it out on the net for more information.
I tested all the LED lights on this TV and to my surprise all of them were working fine. Sorry I could not take a photo of that because; holding the two probes and the camera at the same time was very hard to do. Anyways, the LED’s were in good conditions.
This is the replacement board that I found in my shop. It was not exactly the same but it did the job. Take a look
It is a new learning experience for me. My attention was focused on bad LED light only and not on something else.
I never thought this would be the issue with the display not coming on but it was. Other technicians suggested it was a logic board issue. It might be the case in other repair faults but in this one, it was the LED driver board. Mission Accomplished.
This article was prepared for you by Waleed Rishmawi, one of our ‘Master Authors’ and currently working in the Bethlehem area of Palestine repairing electrical and electronic equipment.
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Parasuraman
April 11, 2018 at 9:58 pm
Expert service! Thanks for sharing!
hongkongpom
April 11, 2018 at 10:56 pm
Edge lit panels are a bad design I think.
Well done on exposing the LED driver board cannot handle the load of the LEDs.
Andrew F. Ali
April 11, 2018 at 11:20 pm
Most times LG TVs are bad backlights. Good repair.
Waleed Rishmawi
April 13, 2018 at 5:33 pm
Andrew, I believe LG is the worse when it comes to repair. as long as the LG device is running, it is fine but once it breaks down, the parts are too expensive to repair and parts only found in LG shops only. that is bad
Andre
April 11, 2018 at 11:41 pm
Good day Waleed
Thank you for sharing your interesting repair.
What was causing the fault on the original pcb?
Is it possible to repair it?
Regards
Andre from South Africa
Waleed Rishmawi
April 13, 2018 at 5:37 pm
Andre: good question. the main cause was the pulse that is needed to turn the back lights on was not preset. the repair would be too much for repair. it cost me only about ten dollars to replace the whole board. I believe in the repair of boards but in this case, It was not worth it.
Suranga Electronics
April 12, 2018 at 11:52 pm
Good Service Job Mr.waleed.
Charles
April 15, 2018 at 12:54 pm
Excellent repair thanks for sharing
Justice
April 15, 2018 at 1:36 pm
Wow again Waleed thank you for such an INTERESTING article !!
Steven david
April 24, 2018 at 12:09 pm
Hi im having the same type of led lights also for my tv (samsung 32 inch) tested the leds n all is good (diode mode) but when i test at the led connector on the power board its 0 volts. But when i switch on n off the led voltage comes up n goes back to 0. So were must i check? I tried the test jestine said to do x10k on the schkotty diode (three pin type)n its shows full scale on my meter. Both ways. Could this be the fault?? Pls advice.