mitsubishi WS55-809 blank screen

i have a Mitsubishi WS-55809 with a blank screen. the power comes on,the green light is constant. nothing comes up on the screen. i came home from vacation turned on the tv and nothing. checked the error code and it comes up 12,which is no error.i tried to scroll through the inputs to make sure it wasn't something hooked up wrong and nothing happens on the screen. any idea on what might be the cause of my problem?