Welcome to the Forum!
Just in case you're on the same path I was (for six months
) you do
NOT set the blade tension on a Jet with the big knob at the back. That's to get the arms parallel and is a very crude tension setting. Get it where it should be and then put a piece of tape or a paint blob on it to let you know when it creeps out of alignment.
You set the tension with the blade flip lever. Spin it clockwise for tighter, CCW for looser. Once you get it set you never have to fiddle with it. Put a new blade in the lower blade clamp, then pop it into the lower holder, get the top end between the jaws and flip the lever back and you're all set!