Pre-war Sonnar 5cm 1.5: disassembly & cleaning questions

lukx

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Hello everyone,

after thinking about it for a long time, I have now purchased a nice pre-war Jena Sonnar, Serial 189xxxx, so made in 1936. It is uncoated as far as I can tell.

IgYi73R.jpg


There is a slight amount of haze on some elements, as well as a VERY oily aperture. I would like to give it a careful clean.

I have removed the outer barrel, the back triplet with shims, the name ring and front element, and the aperture barrel. What remains is the main barrel with aperture and the first (front) triplet inside. That triplet needs to be removed before I can clean the aperture blades and clean the old grease out.

SgBX6ac.jpg


Looking in from the front, there are two notches for a spanner. I have tried to screw it off with my spanner, but so far I have had no success removing the triplet. The spanner is dangerously close to the frontmost element of the triplet, so I have to be very careful and not use brute force. But I see no other way to get the triplet out.

aUR5eSd.jpg


Later versions seem to have the triplet in a brass housing that can be pushed out, but this does not seem to be the case here.

Am I missing anything? How to remove the front triplet?

In case of success: how do I best clean the old uncoated glass?
Is the glass very soft?
Can I use lighter fluid?
Do I have to be careful not to soften the lens cement?

Thanks in advance, have a great day everyone.
 
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Further research on KMZ Jupiter 3s, which are supposedly very close in construction, have not yielded any helpful information regarding the removal of the triplet. I am sure that several people here have done this before, so I hope someone can help.
 
I mustered the courage and used a little more power with my spanner and it came loose. I will now carefully clean the lens elements with lens cloth and lens cleaner fluid. Forgot I had that.
I will leave this monologue thread open, as someone in the future might have the same question. Then this thread might be helpful, like so many threads on RFF have helped me in the past.

Now I can finish the lens and wait for the Amedeo adapter only to then find out my lens needs all kinds of shimming and calibration. The way she goes 😀
 
Thanks lukx for wrapping this up and letting us know how it went. I did read it earlier with interest because I have a 1937 lens that could use some cleaning. But I have not taken it apart yet, so could not really offer any useful insight. I do appreciate your helpful pics and description.
 
This is a good opportunity to collimate the lens, I once cleaned a similar prewar uncoated Sonnar 1.5 which was completely off at infinity and looked to have left the Jena factory like this, with obvious evidences of never having been taken apart before.
 
This is a good opportunity to collimate the lens, I once cleaned a similar prewar uncoated Sonnar 1.5 which was completely off at infinity and looked to have left the Jena factory like this, with obvious evidences of never having been taken apart before.

Yes, you are right. There were several shims for the back triplet, some paper thin metal. One was badly crumpled and torn, I will have to cut that bit out and use the remaining 3/4 of this particular shim. I suspect the collimation will not be perfect after, so we'll see.

I will definitely try to optimize the collimation, I just need the Amedeo adapter first. And a digital Leica would be nice. But oh well...
 
The ring that holds the middle triplet can be very difficult to get out. I have my "$25" spanner, and "Big Bertha" spanner from the 1950s. Sometimes it takes the latter.

I had one retaining ring that was really stuck- ended up forcing it out. You can use the ring from a Jupiter-3 as a replacement.
 
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