This TV wouldn’t turn on and didn’t seem to react to the power button. After awhile, a blink code of 3 slow blinks followed by 1 fast blink would display on the front LED.
A youtube video indicates this can be fixed by replacing the power supply board. A badcaps post indicates a bad Q7120 KIA378R12PI regulator by the power supply connector could cause this error code. I measured the regulator output (pin 2) and it was the expected 12V indicating it was ok. I also had a second power supply board and it measured the same.
Digging through a few other threads with the model, it was suggested to try disconnecting the four ribbon cables going from the tcon to the panel. When I disconnected all four, the backlight came on. I then tried two left and two right one at a time and I was able to get a picture with the two right ones connected and just lines from the two left side connected. This test indicates there was a panel fault on the left side. There is a workaround to this fault by removing the side tabs off the bad side. Removing the bevel from the left side, I was able to access the panel underneath and tore off the side tabs carefully. Reconnecting everything up, the tv turned on with a picture.