u/Global-Fun-1877

At first, the screen went blank but I could tell the back light was still on. Tried rebooting and power cycling (unplugging). Decided to try a new main board. Put it in with a new software load on a USB drive. Tv did nothing, no led lights and the led on the thumb drive never blinked. Tried renaming the software file. Still nothing. Got another replacement main board and had the same results. Checked for voltage using a multi meter. Main board is getting 24 volts. Tried replacing the power board, but I got the same results. Any suggestions?