LG 47LD751 ZB tuner problem

HI All
My TV 47LD751 don't recognize more the antenna signal but work perfectly with an box cable operator, PS4, external HDMI, scart ....
I think it's an tuner problem so i would change the mainboard but i don't know the correct reference to research one on the web.
I downloaded the technical manual but i don't find the information on it. Can somebody  help me ?
Many thanks