CZJ Pancolar 1.8 / 50mm: Sticky aperture cleaning

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Last year I posted about fixing my Pancolar 1.8 / 80mm:
https://forum.mflenses.com/viewtopic.php?t=85324

It came together with the Pancolar 50mm which I'm talking about now. This one worked well at first, but lately all of a sudden its aperture blades got stuck wide open. Probably the old Pentacon issue of degrading helicoid lubes.

Here's some info about how I fixed it, masybe it's useful for somebody.

[simplex]

First of all a link to a YouTube video that was useful while preparing for the job:

https://www.youtube.com/watch?v=yhKxTnQduGM

Second: my apologies for the 'quick and dirty' smartphone shots. I was in a bit of a hurry.

While being pretty sure that degrading lube was the cause for my stuck blades, focusing actually still is pretty smooth. So I decided to stick with the old mechanic's rule: If it ain't broken, don't fix it!

This means, if possible I will dismantle the lens only to its main groups and try to clean the aperture blades without taking the aperture assembly apart.

EDIT: Initially I forgot to mention some important facts regarding the screws holding the rear plate. First of all: skip both small screws, at least for the moment.



Before you start to dismantle the lens, consider whether you have the 'ELECTRIC' version like mine or the standard one. The ELECTRIC version has five large screws on the rear plate, the standard version only three. For the standard version, just unscrew these to gain access.

For the ELECTRIC version, refer to the above image: three of the five screws are placed a tiny bit, around 1 mm, further apart from the centre than the other two. Losen these three screws that are a bit further from the centre to dismantle the rear plate as a complete subassembly. Mostly you will not need to disassemble this group further.

Look at both screws at the top of the image, and you will easily spot the difference.

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Dismantling the lens to its main groups is pretty straightforward: just unscrew front and rear plates, then the front and rear optical assemblys. You'll end up like this:



Top from left to right:
- rear tube
- rear optical block
- front plate
- front optical block
- aperture control ring

Bottom: the aperture assembly

If you do not disassemble the lens blocks, a lens spanner is not required. Simply unscrew parts using your hands. Same goes for the front plate: no friction tool required. Caution: this may be different for earlier or later versions of this lens!

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Aperture assembly up close.




Sticky blades.

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Aperture assembly from rear side.



Aperture assembly after cleaning process. I performed the cleaning simply by soaking cotton buds in Isopropyl Alcohol (99.9%) and very carefully, ever so gently wiping that greasy oil off the blades. Be careful not to circulate the cotton buds against the edges of the blades. Actuate the aperture blades manually several times in between cleaning. Take fresh cotton buds from time to time.

Be gentle, be careful, be persistent and patient. I worked about 15 minutes, switching between front and rear side several times. Then the aperture function was flawless as it should be.

Slight traces remained at the blades, but these appeared to be mechanical wear from normal use.

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Optical front element and aperture assembly to be reassembled: just gently screw them together, no tools needed.




Then the rear optical group will be added the same way.

[Edited for typo error.]

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Now the complete optical / aperture block can be inserted into the helicoid assembly.




Three screws will fit them together.

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There was a decent amount of dirt behind the front plate to be cleaned off - cotton buds after use speak a clear language. This did not come from the blades, fortunately!




Finished.

All in all my assessment to Pentacon lenses, Carl Zeiss Jena as compared to Meyer Optik: most CZJ lenses are much easier to clean / repair if you don't have to disassemble them to the last part. The Meyer Optik 1.8 / 50mm in comparison requires the optical front group to be centered manually on the optical axis by adjusting three set screws. It simply can't be done precisely without special optical measuring tools. No need for such action when working on the 50mm Pancolar.

I'm pretty impressed with the mechanical quality of this lens, not to mention its optical quality. An outstanding lens, highly recommended!