What is Reddit's opinion of SID LED Lamp and TV Backlight Tester for All LED Lights Repair Output 0-320V?

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Ouch! You purchased ALL of the boards but not an LED tester?
At this point you might as well buy that too in order to rule out the LEDs are the problem.

Test each LED strip individually and look for any lights that don't light up and/or blink.

If all strips test fine and have the same voltage then I'd move on to doing the Tcon one connection test to see if either half of the screen works fine. (have one Tcon connection unplugged for a total of 2 tests). If one half of the screen works fine and the other does not then I'd try the tape method.

If the tape method doesn't help then your screen/panel is probably toast. Plus at that point you've exhausted all options minus doing master electrician individual component level testing.

Your backlights are definitely not working, but that doesn't necessarily mean they are the problem.

I would first check the voltage going to the LEDs from the power supply board and make sure each array output was the same. If you have no voltage out of the power supply board then replace the power supply board.

If the voltage out to the LED's looked fine then I would get out my LED tester (which I'm assuming you don't have) to verify any discrepancies with voltage to each LED array. If the LED tester shows voltage discrepancies then I'd take the TV apart and use the LED tested on each LED strip to verify which strip has the problem and replace the LED strip.

If both items check out fine then I'd do the Tcon one connection test to see if either half of the screen works fine. (have one Tcon connection unplugged for a total of 2 tests). If one half of the screen works fine and the other does not then I'd try the tape method. If the tape method doesn't help then I'd check the out put voltages from the Tcon. If those aren't good then I'd replace the Tcon board. If the output voltages are good then next step....

If both halves of the screen react the same as your initial problem them we can rule out a Tcon or screen issue. At that point I'd be taking a wishful guess and replace the main board first. If that didn't work I would replace the power supply board. If that didn't work I would recycle the TV and put the known working parts up on ebay.