Culminar 85 repair

[laptoprob]

Grmbl. Lucky me. My newly aquired Culminar got its aperture stuck and out of circle. Two blades are out of sync.
Now I have to figure out how to disassemble the lens. I found out the outer focus ring cam be unscrewed. But then...

Anyone know the insides of this lens?

Happy holidays everyone!

 

[Sonnar Brian]

It's been a while. I think the front elements just unscrew. I seem to remember using a hollow rubber cork (gromet) to get it out. I cleaned the inner surfaces on one several years ago.

 

[OldNick]

I have a couple of these lenses, one in LTM that I use, and another in Exacta mount, that doesn't see much use, but have never had a problem, so I can't offer help, but will be interested in the outcome.

Jim N.

 

[laptoprob]

OK, please keep the info coming... I will make some pics of where I am now and how I will continue. Not tomorrow though. Other arrangements.


Hohoho...

 

[payasam]

Good luck, Rob. I have a Culminar 85 in screw mount and have come to rather like it.

 

[laptoprob]

disassembly

disassembly

So I made a start. This is a strangely built lens!
I managed to get the front aperture ring loose, but couldn't get any further from the front. The first retaining ring feels very solid, not unscrewing.

 

[laptoprob]

Then I tried the rear. The lens was made for different mounts, therefore the 39mm screw mount is a separate ring. A fine pitch thread unscrews from both barrel and focusing system. Remounting will be try and error!
The barrel ring with the distance markings can't be unscrewed to the rear. I can't find any clues to get the lens further apart. Maybe I shouldn't.
Nest step is the optics.

 

[laptoprob]

The aperture blades are too oily. That's why they are sticking. So I need to get the front element out to get to the aperture, right behind it. But how? Two metal pieces, but not unscrewing at all.

Any clues?

 

[laptoprob]

Front part out!

Front part out!

In despair I decided to take a file and make two notches in the aluminium front ring. That way I can get some grip to unscrew the front ring. Still very tight but it worked.
In the pics you can see the bubbles in the glass, the old glass signature.
the 16-blade aperture is very sticky indeed. I don't dare to take that apart so I will take the lighter fluid first.

 

[laptoprob]

Bad luck...

Bad luck...

One of the aperture blades still won't march along with the others, after washing with lighter fluid. So there remains no other choice but to unscrew the front some more. Vey, very tight. But the whole aperture assembly - together with all optical parts - unscrew together. The wedged tension ring between the focussing ring and the aperture rings separates the two main parts.
But, bad luck, one of the aperture blades is missing one of the guiding notches. The one notch remains in the lens body.
So this Culminar may end up a wide ohhhpen one only. 🙁

 

[laptoprob]

proper (dis)assembly.

proper (dis)assembly.

So now I know how to take the lens apart the easy and the difficult way.
The lens is built of a focusing and an optics piece. Ofcourse. Getting those apart is done without tools: Just unscrew the lens front from the focusing mount. Hold both the aperture ring and the front ring, to avoid excessive strain on anything. Hold the focusing ring and the lens body in the other hand. Do this at 'close focus' setting, the lens being the longest. This way you will avoid deforming the focusing helicoids.
If you have taken the focusing mount apart, assembly is not that difficult. As you can see I took an M-adapter. At infinity the rf ring is flush with the rear of the mount. So you can see when you are (about) correct.
Don't forget to put the focusing ring around the barrel first.
Screw in the fine threads all the way. At the end you will feel the coarser helicoid of the rf ring. Unscrew the fine threaded outer (chrome) ring a bit, just one tick into the rf helicoid thread. Then screw the rf helicoid in. If all is correct, the rf ring is flush with the M-adapter ring. You will now have the full stroke from close to infinity.

Who has a Culminar aperture assembly for me? My optics are fine!