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Post by sevesteen on Mar 11, 2015 19:43:38 GMT -5
One of my M42 lenses is a Super Lentar f3.5 35mm preset. The inner aperture ring is loose, and has to be held to the rear while operating. Held like this it appears to work properly, If I allow it to move forward it can rotate a full 365 degrees, and has to be wiggled back in place. It feels like a clip or set screw or something has come loose. How do I properly take this apart far enough to fix the problem?
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Stephen
Lifetime Member
Still collecting.......
Posts: 2,718
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Post by Stephen on Mar 12, 2015 6:26:25 GMT -5
There are dozens of ways the makers combine a pre-set ring with the aperture ring, but usually a set of cut outs engage a sprung ball or tooth for each value. if it moves back wards ans forwards it sounds like teeth. I would suspect that the outer ring has come loose from the actual ring underneath, and there may be a missing screw hole somewhere on the ring.
Other than that the lens will usually come apart from the front for the aperture mechanisms, remove the front ring, it may need a special spanner(Ebay), and take out the front elements (unscrew), which should leave the rings controlling the aperture exposed.
However makers vary the exact details, and direct experience with lens is usually restricted to top marques rather than the very generic ranges of pre-sets. After saying that, the construction is rarely complex.
I should add some pre-set types take apart from the rear, the main ring nut is released and the whole lens comes out as a unit, revealing the aperture ring mechanisms, but this is more common on telephoto lenses.
Stephen.
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Post by sevesteen on Mar 15, 2015 13:50:02 GMT -5
Update--Set screws in the mount, depth of field scale and focus ring let me remove each in turn to get to the set screws in the preset ring. Tightening those fixed the problem, and I was able to get the lens back together with no parts left over, and appearing to function properly.
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Post by philbirch on Mar 15, 2015 14:06:22 GMT -5
Great job. I'm always nervy about going into a lens.
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Stephen
Lifetime Member
Still collecting.......
Posts: 2,718
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Post by Stephen on Mar 16, 2015 6:55:33 GMT -5
Nice to hear it was a simple cure, pre-sets should not be too complex, it is "auto diaphragm" from the 60's that are the odd designs, before designs settled down.
Stephen.
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