This tv was reported as being dead with no front led and it wouldn’t power up. When I plugged it in, the front led was on but it wouldn’t respond to the power button. Badcaps posts indicated the usual suspects were D607 and C603 on the power supply board. These tested good on my power supply. All voltages appeared stable and present so the main board was getting power. There is an LED on the power supply board itself and it was flashing a 5 blink code. Searching online, I did find an eeprom for this model so I tried freezing it and it made it worse. The front LED was no longer lit after freezing. This test lead me to suspect bad bga connections on the processor.
LG LV series are known for bad BGA though I had read that the LS series had this problem as well. I heated the processor up and when I plugged in the TV, the front led came back and I could turn on the TV. With BGA failures, the lead-free solder balls crack over time and have poor connectivity. Heating up the processor will expand them enough to make contact.
The proper repair in this case is to get the processor reballed which is a bit expensive. I have found previously that baking the board is a temporary fix before the problem comes back. I did try to reflow the IC at 430 deg F with my hot air tool and flux but it didn’t work.
I was able to find a used board online but the problem may reoccur with a used board.