HiSense LEDN40K360P, no picture and no sound

Hello good people,

I have some electronics training but perhaps not enough to resolve this problem.

I have a HiSense LEDN40K360P which has no picture and no sound. The standby light does come on when the TV is plugged into a source. The main light also comes on when the TV is switched on

The TV is equipped with the ff boards RSAG7.820.4737 and RSAG7.820.4833. 

Regards, Ken