[travfar]

I just bought a Pentax A 50mm 2.0 off of Craigslist. It was cheap and I was in a hurry and didn't inspect it that well. All I did was make sure the aperture worked so I could see if the lenses was clear. I didn't try the focusing ring. Turns out that's busted. Turning the ring doesn't do anything. It's kind of stiff and the lens doesn't move. Is it fixable? Could be that the gears are just stripped. Fixable or not, is there a tear down guide for it. If it's fixable, I'd like to try to fix it. If it isn't fixable, I'll use it to practice taking lenses apart.

What do you know? I binged it and found a site telling me how to fix a similar problem.

http://grantharg.tripod.com/CameraRepair/M50mmfixa.htm

[Just1MoreDave]

That site does a pretty good job of explaining it. Step 6 shows the jammed part. I repaired an M50/2 with a similar problem without any guide. It looks like these instructions allow you to avoid unscrewing the focus helix, the large threads that move the lens in and out. If you unscrew it, the threads have multiple entry points, but only one is correct. Trial and error will work. Also, keep track of all the electrical contacts and small parts when you remove the mount.

Used lens buyer warning: if the rubber focus grip is loose or missing, check the focus ring to see if it turns. When the focus ring jams, the first thing someone tries is to turn harder, then a lot harder, then the grip comes off. I don't know if the 50/2 lenses are more vulnerable to this jam or just more common.