LG 55UB850V no sound or picture.

[bonesy]

Hi folks I've got the above set which obeys remote commands O.K. so switches on & off from st-by,but never shows sound or picture.front st-by led shows no flashing codes,but on psu board there is a LED marked LD701,which after around 30 secs continuously flashes 5 times,there is a stable 12 & 24 volt Lt lines & also a 3.5 volt.Has anyone had one of these or similar,or possibly a circuit diagram.
I've done the usual pressing menu shining  light on screen to see any display but no go.
many thanks John.