Quote Originally Posted by Chris G View Post
Yes, there is a tiny amount of play. Just force it back and forth between the stops and it should finish the cycle. I have had the same problem before, I twisted it fairly hard, but want to be careful about putting that advise out there!

The cause was the pins on the lens side were sticking for the first part of their rotation. Lens dis-assembly, cleaning and light lubrication was required.
Yes! I forgot about that. That is likely to be the problem. It is due to old lubricant which has thickened. As Chris says, move the lens rapidly clockwise/counterclockwise and it should complete the cycle. If not, warm it up. A sunny window might be enough, or putting it in an oven which is not above 120 actual degrees F, or a hair dryer blowing on the lens (being careful not to overheat any spot). Jiggle it periodically until you get it to release.


Once the lens is off, it is not difficult to get into the lens through the back to clean and relube it.
In this thread over on P.nut I explain how to do it:

http://photo.net/medium-format-photography-forum/00bG13

One thing I said in that thread was Koh's is always an option for repair. I was wrong about that, obviously. They have stopped doing repairs.