Stuck focus ring-carl zeiss jena 50mm f3.5 Tessar - Solved

[mareinke]

In Carl zeiss jena 50mm f3.5 exa project, I've almost cleaned the glasses and aperture blades, but unfortunately failed to figure out how to
remove the focusing ring, because there's no stopper pin or screw at all.

any clue about how to do this?
your help is appreciated.

marco.

[jhayashileite]

I see some screw holes in the rings. Were you able to take them off? I have a Biotar and its focus ring is removed by releasing some screws and pulling it upwards.

[mareinke]

[gi0rgi0ba]

[mareinke]

Hi gi0rgi0ba,
Thank you for the response.

Currently, the rear assy (left one) is still a puzzle to me, I couldn't separate the focus ring from the bottom part. there's a focusing stop pin working inside, but don't know how to reach it, so I did simply pour some lighter fluid from outside, hope this works.



The process log for somebody else.

1. Unscrew the 2 helicoid alignment screws, rotate the front assy clockwise to take it out.
BTW, align the 2 red triangles(mark 1 and mark 2) will simply assure the helicoid position.


2. After front element is separated from rear assy, you can start lubricate the helicoid.

3. Aperture assy
step 1: unscrew 3 secure screws in the top aperture ring and then pull it out.
step 2: unscrew the other 3 screws in the retaining ring, and rotate it counterclockwise. it was not easy, if too tight, apply lighter fluid, if still not work, special wrench might be required.
Step 3: reach the front assy, take out the front cell using spanner wrench
Step 4: you are about to see the blade nest and the relevant coupling pin that secures it. unscrew the pin screw, take out the nest.
Step 5: Now, you can see 10+ aperture blades laying on the bottom of barrel, pour them out and do what you want.



Marco

[gi0rgi0ba]

hi Marco, could you send me the image of the rear part of the lens?
I separated the helicoid by removing the 2 screws (see my picture above)








here are some images of the lens during the cleaning.
Let me updated
Cheers
Giorgio

[mareinke]

Hi Giorgio,
It looks like no1 is locked by no2, and no2 is probably movable and could be secured by the 3 screws in the bottom part, am I right?
I guess my 'no1' and 'no2' are probably stuck together, that's why the focus ring works normally but never got a chance to come out.
I'll try more Naphtha to turn it out.
Thank you so much for doing this, it's really helps.

Marco

[gi0rgi0ba]

Hi Marco, did you unscrew the three little screws from the no1? probably your no1 is stuck as you said. Use and leave act for a couple of days specific lubricant to unstick it. then gently move left/right the n01.
BR
Giorgio

[mareinke]

[mareinke]

Hi Giorgio,
After pouring enough naphtha and acetone, the whole process turned out to be easier. I held the back assy tightly, twisted the outer focus ring with enough force, and then it came off.

Focus stopper(No1) is a movable ring with no screw thread, 3x screw holes can be found.
Side screw(No4) in rear mount(No3) is to hold the focus stopper(No1) in place.

Thank you again for everything you’ve done.


Marco

[gi0rgi0ba]

Good job, Congratulation!!!