Check main cord then fuse if fuse is blow then check diodes, power supply trnsistor also resistence.

Most likely your convergence board is bad. If you have any electronic repair experience, you should be able to locate the convergence driver board. There will be two large black IC's mounted to a metal plate and they will start with the letters STK. Disconnect this board and if the set starts up, it is bad. There should be a number on the board. This will be a Samsung Number. Go to Samsungparts.com and enter the part number into the right box and see if it is still available. If it is not, you could always go to ptscorp.com, get their telephone number and call them about rebuilding your board. Good Luck!