Samsung un70tu6985f when I turn the TV on the black lights turn on and

I have a. Samsung un70tu6985f when I turn the TV on the black lights turn on and off and the red light blinks twice I replaced the supply board still did the same thing I am plugged the supply board cord that goes into the main board and the black lights light up full. I was told that it was the main board bought a new main board plugged plug everything accordingly and it does the same thing happened just black lights turn on and then turn off in the little red light at the bottom blinks twice