50mm f3.5 Elmar, stuck diaphragm

[Pyrogallol]

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I just picked up another early 50mm Elmar, un-numbered, nickel, "short" version. It is standardised, coated and 7 o'clock, so probably upgraded at some time..

It was very dirty when it arrived and the diaphragm was solidly stuck at f18. A cleanup and drop of penetrating oil in the edge of the diaphragm adjustment ring (see tip of pencil)  has freed off the adjustment perfectly. I have found before that a drop of WD40 will release the decades of dust and grit that gets in the tiny gap around the aperture ring without finding its way inside the lens, This time even WD40 did not work but penetrating oil did. The "experts" will say I should not do this. I have found the same trick works with early Nikon rangefinder 35mm lenses.

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[TomB_tx]

I've used the same trick with fine instrument oil. Use sparingly - I've never had a problem.

[jerzy]

vor 2 Stunden schrieb Pyrogallol:

This time even WD40 did not work but penetrating oil did

you need to be very carefull when doing this, a bit too much and it may penetrate into the space where aperture blades sit and even on the nearby glass surfaces.
This is how the optical barell looks like - aperture setting ring is connected with 2 screws (only one shown here) with the blades ring. There are 2 realitevely big cutouts in the mount of the optics and this is where any oil or WD40 may easily penetrate inside the lens. 
I believe that your lens was stored for a long time in a humid environment, we may see that as well nickel plating is damaged. If possibly give the lens full CLA (and polishing of nickel plating). 

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Edited July 9, 2024 by jerzy