Sound and no picture

@marjorieronzani you are not saying if your power LED blink when your pictures is dark. First you want to try all other video inputs, things like HDMI, Component etc. Next try to see if your TV still shows the TV menu when you push that on your remote.

Now turn the TV to a channel where you can hear the sound. Next, use a flashlight and shine the beam at an angle against the screen. Do that in a darkened room. See if you can make out shadows or shapes. If you do, then it is your backlight that has failed. If you do not see anything, unplug your set and remove the back cover. Then visually check the boards for any obvious damaged components.

Check all the wiring and unplug the wires and plug them back in, make sure they are properly seated. Post some images of all of your boards with your question. Use this guide Ajout d'images à une question existante for that so we can see what you see. It is possible that this is either a power board or a backlight inverter.

Your TV uses CCFL tube as backlight. It is possible that these have burned out. Those function in principle the same way as fluorescent light bulbs.

If you have any trouble translating this, let us know what your native language is. We can always try to rephrase or translate the more confusing issues. Welcome to iFixit!