I am fixing this same model of Samsung HCN653W TV as well. I have the service manual and have started digging into it...not much success yet. My failure mode is similar, too - the TV will power up (play it's power-up jingle) then the screen comes up with static for about 3s and then it powers off. I can even see Antenna 2 in the upper left-hand corner of the screen during those few moments.
Anyway - BTDT advice on this one is appreciated. I've had success repairing other TVs of mine, just looking for a little advice with this one. I have the tools I need (oscilloscope, multimeter, soldering iron, etc.). Hopefully the tips and work we do here will lead to a solution that we all can use.