I recently bought a the 50mm f1.4 hexanon in "excellent" condition, and for the most part it is, but the aperture ring is jammed and stuck on 2.8. I am getting a full refund, but don't need to return the lens, so ihave nothing to lose trying to repair it myself. It doesn't appear to be a problem with the aperture blades, as they open up when I move the little lever on the back. So i think it is just the dial. I have Googled for repair videos or instructions on blogs/forums, and not comeuppance with much, but before I start, I wanted to at least ask the question here. Any tips? Much appreciated.