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Can't find any info on the web so I'm hoping someone here can help. The TV has a backlight during initial powering on but then shuts off after 3 seconds. On my PSU it is flashing 4 times on the LED at LD701. PSU is EAU63149401. It does have sound still and I also did the flash light test and there is an image.
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@angry_jay this "It doesn't have sound" is not connected to the backlight. So, there are other issues with it as well. This "flashlight test and there is an image" is definitely a backlight issue. I suggest that you measure the voltages form the mainboard to the power board and see if they are what is silkscreened on the power board. In particular it's the BL_ON that would be of interest. The sound is managed on your main board so right now missing sound and missing backlight could be a main board issue. Those could also be separate failures, backlight array and main board. We do need to narrow it down. Let us know about the voltages and post some good pictures of your boards and the interconnect cables with your QUESTION. That way we can see what you see and hopefully get this TV fixed.
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Sorry I meant to say it does have sound still. I edited my question. Auto correct.
The test points at P210 and 211 are reading 49.4 volts after the backlights turn off. During the initial start up it is reading 76.8 volts. There is a DRV-ON test point near LB201 that is reading at 3.10 volt
@angry_jay that sounds about right. Seems to be your backlight array.
I was able to test all of the test points for the LED back lights that is located on the power supply and it look like a LED strip itself is to blame for this. It's voltage is way lower than the rest of them. So I'm guessing the LED blinking 4 times means a LED strip problem. Hopefully I don't waste my money on getting a new one.
@angry_jay it sure appears that way. Not all TV's will give a blink cade with failed backlight strips. Some give it since the board "measures" that there is a voltage issue on the backlight connectors. Replace the strips and -re-evaluate. Main point of caution is the LCD panel itself. They are thin and love to flex. So, make sure you got some help to prevent that from happening.
Different model LG but same idea. 42" LG TV LED Strip Replacement Tutorial
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Hi @angry_jay,
Here's a composite image showing the no video/normal audio troubleshooting flowcharts from the service manual that may help, at least to isolate it to a board perhaps. Note: module = screen.
(click on image)
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The most likely cause of a backlight problem on an LG 49UB8500 is a faulty backlight inverter board. This board is responsible for providing power to the backlight and can become damaged over time due to wear and tear. To fix this issue, you will need to replace the backlight inverter board. You can find replacement parts online or at a local electronics store. Once you have the new board, you will need to remove the old one and install the new one. Make sure to follow the instructions carefully to ensure that the new board is installed correctly.
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