LG 42LV550T no sound or picture.

[bonesy]

This one when plugged in comes on red st-by light,press power button r/s you get a white light,flashes two or three times then solid white.At no time do you see even a flash of back lights on screen.I've pressed menu button & shone torch at screen,but no sign of back lights at all.The multi connector that goes off to the SSB,all voltages as marked,but one marked drive on,which I guess is for the LED back lights,doesn't seem to move at all.Back light control is very complicated,with a bank of transistors & a micro i.c. on the back of the board,I've tried to see if any drive voltage comes up,but no sign.No signs of stress on components in power supply or ssb boards.