in my ipad2 early model, i found a solution. just shine a good led torch on the ipad screen. try rebooting the ipad OS. its resets the backlight to ON. solved my backlight problem. to make my situation harder, i dont have any volume or power buttons. as i have damaged the ribbon while opening it. nevertheless, with the help of a led torch, I went to settings > general > reset > network settings > reset and confirm. that made the ipad reboot and vola! backlight is bakc on! hope this helps.....
regards
apple sucks a$$