Tv turn on then right back off

Gerald George  most likely that it did not pas the POST (power on self test) or an issue with the power board. We need to know what model your TV is. Most likely is that you need to remove the back cover and check the power board. The connector from the power board to the main board cable is the one of interest. The voltages for that connector are printed onto the board. You need to check those first so we know the initial condition. Post some good pictures of your boards and interconnect cables with your QUESTION so that we can see what you see.在已经存在的问题里加入图片