I get the feeling that you are referring to tension and not blade clamping? If so, what Roberta and Kevin have suggested would make the most sense. What you need is for all the tension adjustment to be in the most relaxed position so that when you insert a new blade and get both ends clamped in place, then you apply the tension by moving the slider until it feels like you have it tensioned correctly. A ping of the blade will tell you. Now, if you have already done that, you may have damaged the tensioning mechanism or knocked something out of whack which might necessitate the disassembling of the saw. There is a rod that connects from the slider lever clear back to the rear of the upper arm and moves a wedge and that in turn forces the upper are to rise and apply the tension to the blade. There is a very good set of videos on Youtube that shows how to do the disassembly of a Dewalt and since the saws are so similar, I'd think that you could dope your way through it. Good luck and do keep us all informed of your progress and just what you find out. And also, WELCOME to the Village.