TV turns on but no picture. The status light works. In the upper right hand corner of the power board, I am measuring voltage on the cabe that feeds the main board. I have 3.5 volts on the bottom terminals (like I should) and I do not have 12 or 24 volts on the upper terminals which I should. My thinking is I need a new power board. I was watching a youtube video from shop jimmy and the video said if you have standby power the main board is bad. The video did not address the missing voltages? Any advice on if I should purchase the power supply board or the main board?

Televison & Video - LG - 47LN5400 47" LED TV 1920x1080, 120 Hz. HDTV