Samsung TV Turns off after a few seconds red and green light flas

You are going to have to troubleshoot all the boards in the television until you find the problem. Start with power supply board. This part usually goes bad due to overheating and faulty components. You must check for brown spots on the boards , that are signs of overheating. Look for bad components like bulging capacitors and burnt resistors.Look for bad connections, like cold solder joints. you must be very careful working on the power supply board as it does have high voltages they can be very dangerous to the inexperienced user. Never test anything with the power on or connected.Use anti static protection straps and gloves around all the chips and microprocessors to avoid damaging them. Check all the other boards for the same problems. If you can find no problems, Then it is time to get help from a service center where they will have all the necessary testing equipment, To give the unit a more thorough testing for faulty components.Hope this helps you with your problem.