A white line appeared on the screen when the TV was in standby mode.
This is an inspection operation of the Panel Refresh function.
When Panel Refresh is performed, after about 1 hour, a white line moves from the top to bottom of the screen, and checks the pixel conditions of the TV screen.
When Panel Refresh is performed, after about 1 hour, a white line moves from the top to bottom of the screen, and checks the pixel conditions of the TV screen.