To make adjustments to the Blacklight function enter the Menu system by holding down the Menu button, 

then using the + button next to the Select button repeatedly press until you see "System" in the display, 

press the select button, then again repeat press the + button until you reach "Backlight" and press select. 

Here you have 3 options to pick from "Time Out" "On Level" or "Dim Level" 

Select Time Out and select "Off"