if you're lucky, it's just a software problem
check the correct version on the label on the tv back
LE730E or LE730ENET or LE730ENET[B]
and download the latest software from sharp website
copy the file on an empty usb stick and insert it in the tv
plug AC mains
if standby led start flashing, sw upgrade is in process, wait until the standby led goes off
unplug the AC mains and the usb stick, wait 1 minute and reconnect AC mains and power on the tv