Hi Ron, I will state here that I am not a camera repair person so anything I say you will have to do at your own risk. Also, the Focotar 2 seems to be slightly different in in design. However, I don't think it's a good idea to remove the set screw first. The trick to getting into the lenses (Not the Schneider Focotar... Completely different) is to first remove the larger retaining ring at the back of the lens. You will not be able to remove the retaining ring if the set screw is not in place. When I say trick I mean it. Those rings are the tightest set rings I have ever encountered. It's as if the assemblers back in Wetzler were playing a cruel joke on the world or just did not ever want anyone to ever get the lens apart in the future. If you are not careful you can ruin your lens right at the start by buggering this ring. If you are good with tools you might try it, but with a Focotar 2 I would send it out to a professional, which is what i did with mine. So... put the set screw back in, remove the ring, then the remove set screw and then the lens will come apart. Beyond that I can't help as I have never opened the Focotar 2. If you want to send it out I highly recommend Allan Starkie at CamerworksUK in England. He did a total rebuild on my Focotar 2 and it came back a new lens. He did what a name repair person in the US was unable to do. Sorry I cannot be of more help Ron. Best of luck with your lens. The Focotar 2s are remarkable lenses....Robbie