Power supply replacement and still no power!

I had the blinking red light as i tried to power on my TV. No go!! So next step is i read all the reviews on what to do, so first step possibly power supply. So i replaced power supply board on my 55” Samsung TV (UN55D6005SFXZA) and that wasnt the issue. Doing the same TV comes on samsung Smart TV logo comes up then shuts off within 5-7 seconds. So what other problems can it be? Would the motherboard cause this type of issue as well. Do i even need to try and fix?