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Hello, This issue is either caused by the power supply board or the Mainboard. What you need to test is that the 5 volt line is present on the power board using your meter. Also, when you unplug the set (until the light stops blinking), and then plug it back in, does the light start blinking immediately, or only after the power button is pressed?
The voltages are all labeled directly on the power supply board near the connectors. You will see 5, 12 and 24 vdc stamped on the board. Check and see which voltages are present at plug in, and also at power up (upon pressing the power button). It is most likely that your power supply board is faulty, but there could also be an external fault causing this. Please reply back when at the set with meter in hand.
I have to run out for the day so I will open the question to other experts to assist.
My apologies, I posted to this question accidentally.
Best of luck with your LG issue.
OK, did you replace any board in TV so far?
Yes, problem appears to be the main boar because voltage readings from the power supply are normal so swapping the main board would help to get the TV up and running.
Please check with following board supplier and ask if they can provide required main board as currently it is out of stock..
I trust my input will help you out. Please feel free to respond if you have any additional questions.