Sceptre LCD TV power come on, but there is no picture or sound.

There are two easy fixes you can try. Both require you to take the back panel off. If you are not comfortable doing this, take it to a repair shop.
UNPLUG IT.
Place the TV face down on a soft/solid surface.
After you get the back panel off, there are three silver boxes. There are white and black wires leading from the off switch to the top silver box. Take the cover off that box.
Inside is a ceramic fuse. Test that fuse. If it is blown, your local electronics shop can find a replacement.
If not, disconnect the white and black wires from the PC board. Remove the 6 screws holding it in place.
Look for scorch marks under the board.
Cut a thick piece of plastic and tape id down over the scorch marks.
Re-attach the board with the six screws and re-connect the black and white wires.

Turn the power switch to the OFF position and plug in the TV.
Turn on the power switch while WATCHING the board you just removed.
If you hear a sizzle, turn off the switch and get a thicker piece of plasic.
If not, the TV should come back on.
Re-assemble the silver box and put the back on.

Hope this helps.

If there is a humming sound (very small) then you have most likely blown something (can berepaired)., also there may be some trouble with the cables if if there is any color it is most likely a communication problem..sorry tough to solve problems 500 miles away