No picture but sound is still there the lcd screen is blank

The problem you have mentioned can be either caused by a backlight inverter malfunction or T-COn(LCD controller malfunction). Take a flashlight and focus it on the screen from a close distance. See if you notice a dull image. If you do then the backlight inverter is the source of the problem otherwise, its the LCD controller. Both of these boards are pretty easy to replace, if you have worked on electronics such as computers below, as it only involves unpluggin cables from the older boards, and plugging them into the replacements. If you wish to do it yourself let me know the make and model of the tv so that I can help you find the replacements and advice you on replacing them.

Sai.