I have no picture

@irwinmorey this could be a power board issue if your backlight does not turn on, or a LED issue as well as a T-con board issue. Unplug the set, remove the back and take a look at the boards. Check for obviously damaged parts like leaking, domed looking capacitors etc. Post some pictures of your boards with your question so that we can see what you see. Use this guide for that. Once you have those images we can point out some test points as well as possible fuse location on the T-con board. My first suspect for this is your t-con board.

This is a T-con board for your model TV and it shows the fuse location. Test that for continuity. This particular T-con board has a relatively high failure rate. Proper substitutes would be:

BN96-28943A

BN96-28944A

BN95-00944B

BN95-00944C

All of them are available at places like this