I have sound but while I was watching it the screen went black ,now I have sound but no picture.

If backlights are working issue is probably with t con board since you have audio,

LG LED TV has no picture (black screen) but still sound ...

www.tomsguide.com/answers/.../led-picture-black-screen-sound-fixed.ht...

My 32' LG LED TV has suddenly lost picture! The sound is all right but the Screen is pitch black. After switching it on the picture flashes for a second and then the screen goes completely black.

LCD Easy Fix (sound but no picture) - YouTube

? 4:52
https://www.youtube.com/watch?v=IBRE1Dcyxp4
Jan 13, 2012 - Uploaded by Clay Whitehead
TV Has Sound But No Picture Troubleshooting Guide - Duration: 2:30. by Repair.com 472,733 views. 2:30. LG LCD TV REPAIR -NO PICTURE ...

backlight may have gone if your tv has one

please see your other post for response

my TV has a half black & half white screen & half of the TV is showing the picture including the normal sound,what can I Do,?

Check and replace the back-light inverter baord.

I would love to help you.
Please respond by PRESSING REPLY OR COMMENT
Did you experience any storms recently? IE. the power cut off unexpectedly?
Bruce

Replace digital board. Common for this set.

Could be the power supply gone bad.
No easy solution I'm afraid.