Pentax K2 Stuck ISO Ring

<p>The K2 has an ISO selector ring that is concentric with the lens mount. It's actually in two parts. The section adjacent to the lens mount has an index mark and two grippable parts, and the section further inward has the ISO values. These two sections are supposed to move against each other to adjust ISO values. There is a release button, just below the right side grip (facing the camera), which is meant to be pushed in, I'm thinking, but this one won't, or it will, but just barely. And because of this -- or at least, I'm thinking because of this -- the ISO ring can't be moved. Actually, with a lot of struggle and wrenching on it (by hand) and mashing at the release button, I can get it to travel from a max of ISO 200 to a min of 64. But it is quite difficult to get this much movement out of it.</p>

<p>So I guess I'm wondering if there might be something I can do to free it up, short of having to dismantle the mount to get to it. Yes, I do a lot of my own camera and lens repair, but I've never opened up this sort of ISO setting system before. It would be nice to know what I'm getting into before I do it for a change.</p>

<p>Any advice about what to look for or pointers is welcome.</p>

<p>http://pdf.textfiles.com/manuals/CAMERAS/VINTAGE/k2_service_manual.pdf</p>

Mine had the same problem when I got it. I eventually got it freed up by jiggling it back and forth through the range that it would move, and gradually the range expanded. IIRC, it worked best to have the lens off, so I could put my thumb on the release lever while gripping all around the ring with fingertips. Don't try to hold the exposure compensation ring still; let it turn with the ISO ring. I've found the ISO ring is more likely to skip forward if both rings are moving.

<p>Thanks for the responses. Appreciate the link to the service manual, John. But it didn't even show this area. Still I'm glad to have it.</p>

<p>Jerry, I didn't want to hassle with the process you described, so I went ahead and got out my screwdrivers and tweezers and went to work. The entire assembly is rather cleverly designed and understanding it helped me arrive at a solution -- eventually. The tab that is pushed in is on the center of a bowed flat piece of stainless steel, it looks like, a flat spring, in other words. On the camera side of the tab (as opposed to the lens mount side), there's a small pin that engages a series of teeth. This tabbed spring sits in a small slot and presses against an inner ring, at which point it disengages from these teeth, which allows the rings to rotate. The tab of the spring, in its relaxed state, remains engaged in the teeth. The problem I had with it was I couldn't keep the tabbed spring in its little slot. It kept popping out, and the result was its jamming up the way it had been before I dismantled the mount, preventing the tab's pin from being disengaged from the teeth. I suspect that there's some wear somewhere that allows it to slip out. After reassembling the system maybe four or five times, only to have the tab/flat spring slip out again, I finally gave up. So I just removed it. There is enough friction against these two rings that are used to set the ISO such that it is still not an easy process to change ISO even without the tabbed locking spring in place. And I even lubed the assembly lightly. So I'm not concerned of inadvertent movement of one or both of the rings. I feel satisfied that this rather unorthodox solution will actually serve me just fine. And I feel relieved, to be honest, that I was able to come up with a solution that works as well as it does.</p>