Screen completely dark? Maybe bad backlight or power supply?
Or does it light up, but nothing shows up on the screen? Mine went blank within a year or so. But by messing with the contrast wheel and pressing and twisting on the housing, I found the picture would come on. (The contrast wheel only had a tiny spot where it worked, even when it was new, so don't touch it after that!) Then the scope worked when you pressed on the bevel at that certain spot, lol. So I found if I jammed a toothpick between the housing and the screen right there, tada! Working scope.
Edit: I still keep it around, in case I need a battery powered scope. I just checked it. Still working with the toothpick hack.
I can't see the toothpick; it's completely hidden, pushed down below the bezel. But IIRC, it is along the bottom of the screen, about one third towards the right, near where the contrast wheel is. If your screen lights up, it might be worth a shot playing with the wheel while pressing the housing on that spot.