I am not sure but it should be the knob assembly. What the knob does is
simply engage/disengage the AF shaft underneath the hood. The mechanism
itself is not complicated, and can be accessed to by removing the rubber
cover. The plastic knob is held by a screw which is covered by a piece of
plastic (taped). You need a fine needle to remove the plastic cover
carefully. The plastic knob has a fixed contact brush underneath so be
careful. However, I do not understand why unmounting the lens would unjam
the lock.
Alan Chan
http://www.pbase.com/wlachan
I found a dealer in Germany, who's selling a used FA 100/2.8 MACRO in good
condition. The price is ok because it has (according to the shop) a problem
with the focus range limiter. When the knob is on "FULL" and you focus at
close distance it locks the focus range to the close-distance side. You
have to unmount the lens to have full focus range again. Would you consider
this a serious problem? What could the problem be? Do you think it could be
easily fixed?
