WHAT NOW? UN50TU8000FXZA No Picture! New power and main board.

UN50TU8000FXZA

I’ve replaced both the power supply and main board and still no picture. LED’s light up when cable from power suppply to main board is disconnected. Cannot see anything with flash light test. What’s next?

crwdns2934089:0crwdne2934089:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2889612:0crwdne2889612:0 0
crwdns2934285:0crwdne2934285:0