I think you mean LCD, not LED. If you can't see anything, then it may be toast. I have read a bit about the D4 (And sold a few) The LCD has had many problems. I know that is not what you want to hear. The LCD's are probably going to be impossible to find too with Alesis big change over. I did a Google Search for you and located about 15 threads where people were looking for D4 LCD's. There may be a contrast control parameter as many of their other priducts have them, but I suspect you may be SOL. Good Luck
Fangar