model: ua40f5500ar | no display

mark aspacio this could be a power board issue or a T-con board issue (No Video : If the problem is No Video but BLU is on and Indication LED is blinking repeatedly and faster than normal booting, replace the T-Con Board.) as well as a LED backlight failure or bad LVDS cable. You always want to check all video input sources, like HDMI Component etc. to make sure that your have no video with any of the inputs. After that you will have to remove the back of your TV (after you unplug it) and check the boards for obvious damage like domed, leaking capacitors etc. It is most likely your power board, so check the fuse for continuity on that. If those are all good and your board looks good, measure the output to your LED BKlight with a multimeter. Let us know what that voltage is. You will have to help us to help you by posting some good pictures of your boards with your question. It will allow us to see what you see and to further identify points for further troubleshooting. For that, use this guide

Here is a view of the boards that should be identical to your TV

and here are the connectors to check