My apologies if you know this, but in both the GFL and WL fine focus is tightened and loosened by turning the fine focus knobs against or away from each other.
Are you sure about this? It is been a while since I had one of these apart but I think to remember a fine focus shaft that runs from one knob to the other. I might be wrong though.
Thanks 75RR and Bob,
Funny ! as occasionally mentioned on this forum, not all Zeiss Standard microscopes of the same model are entirely identical to each other!
I own two GFL scopes. One is in use, the other, which I believe is somewhat older, is under reconstruction. On both of them, the coarse focusing behaves exactly as described in the manuals: a special single control knob, coaxial with the coarse focusing knob, and fitted between the focusing knob and the arm, controls the tension of the coarse focusing movement. The fine focus knobs are NOT the same
. On the scope in use, the rightside and leftside knobs can be rotated in mutually opposing directions (from the operator's point of view). Such manipulation seems to affect the tension, yet since the fine focus works nicely I will not test it too much. Also, the knobs are uniformly knurled, no small screws on them.
In the scope under reconstruction, the one that bothers me, I cannot rotate them in opposing directions (I will not attempt with tools, though). Each knob has a small set screw that apparently locks it to the shaft. Whether this screw and its function are related to the tension of the focusing movement - I doubt but cannot say.
Bob, thanks for the tips. When I figure out what to do they will certainly help!