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Preset ring for Sankor 2.8/135 not working
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PostPosted: Mon Jul 21, 2014 1:56 pm    Post subject: Preset ring for Sankor 2.8/135 not working Reply with quote
I have this lens and it seems something is wrong with the ring for presetting the aperture. It does not stop the
aperture adjustment ring from moving. Perhaps I am using it wrong or it is not working. Any advise is welcome.
It is the outer zebra style ring on the lens. Thanks.


PostPosted: Mon Jul 21, 2014 5:12 pm    Post subject: Reply with quote
Does turning the aperture adjustment ring turn the ring for presetting the aperture? If no, this is probably okay, otherwise the two rings are too close together -- there should be screws attaching the rings to whatever they move; adjust so rings move freely past each other.


PostPosted: Mon Jul 21, 2014 7:09 pm    Post subject: Reply with quote
visualopsins wrote:
Does turning the aperture adjustment ring turn the ring for presetting the aperture? If no, this is probably okay, otherwise the two rings are too close together -- there should be screws attaching the rings to whatever they move; adjust so rings move freely past each other.


What happens is I set the preset ring and then when I turn the aperture ring it goes up to the spot where it should be stopped and then starts turning the preset ring also as you said. However the rings don't appear to be very close
to each other.


PostPosted: Mon Jul 21, 2014 7:28 pm    Post subject: Reply with quote
Its working as intended, up to a point. The aperture ring gets to the minimum aperture position, and then pushes the preset ring if forced further. Mine works the same way. But your problem is that its too easy and does not require greater force to move the preset ring. There is a detent with a spring internally that is not holding strongly enough to provide enough resistance. I suspect that part may be worn out (such as the aluminum around the detent hole is so worn the detent doesn't stay in the hole) or the spring is now too weak.

I can see how this can happen on such a well used lens. The only way to fix this would be to open up the mechanism and see whats going on. Personally I would live with this and use it as a pure manual lens.


PostPosted: Mon Jul 21, 2014 7:51 pm    Post subject: Reply with quote
luisalegria wrote:
Its working as intended, up to a point. The aperture ring gets to the minimum aperture position, and then pushes the preset ring if forced further. Mine works the same way. But your problem is that its too easy and does not require greater force to move the preset ring. There is a detent with a spring internally that is not holding strongly enough to provide enough resistance. I suspect that part may be worn out (such as the aluminum around the detent hole is so worn the detent doesn't stay in the hole) or the spring is now too weak.

I can see how this can happen on such a well used lens. The only way to fix this would be to open up the mechanism and see whats going on. Personally I would live with this and use it as a pure manual lens.


Thank you, that is exactly right. I do feel some resistance when I reach the correct aperture so I could become
more sensitive to it. Also if the focusing ring moved more easily that might help me to notice the preset. Do you think I could lubricate it or loosen it somehow?


PostPosted: Tue Jul 22, 2014 12:32 am    Post subject: Reply with quote
Simplest solution for stiff focus on these things is treatment with lighter fluid (naptha).

This is not an ideal fix. Best would be a total dis-assembly. removal of old grease and re-grease.
But that is too much work for me, usually. Getting helicals to fit together again is for people who like 3D puzzles.

Try this, if you want to try the easier method. The risk is low, but you could get into problems.

- remove the lens mount to have better access to the back.
- work the focus mechanism and looking inside you will see that the helical threads are visible.
- put a little (just a few drops, maybe 3-5) on the helical threads at different points. Use an eye-dropper, a syringe or similar.
- work the helical back and forth, best with the lens upside down, so the naptha gets a change to flow through the threads from back to front.
- you will probably find that focus is now quite loose !
- but this will not last. As the naptha dries it will tighten up again, but usually not as stiff as before.
- A couple of more treatments might be needed
- risks are -

that the old grease will not just be re-moisturized, but may start to turn into loose particles. The helical may feel like its "grinding" when you move it.

that the thing may get too loose (no more dampening). don't overdo the naptha. it may dissolve all the grease.

that some of the naptha may seep into the optical side and get on the optics. This lens is really easy to open and clean, so thats not much of a risk. but again, dont use too much naptha.
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