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Mike Kovacs
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, July 11, 2005 - 08:40 am: | 
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I have this M42 mount Carl Zeiss Jena Tessar whose helical is driving me crazy. I obtained this lens fully disassembled and I'm have a hard time getting it back together. It has an automatic diaphragm and I have a Practica body to collimate it on.
If I get it started (holding in the aperture pin at f/22, sliding the guide screw into the slot), I have to rack the focus back so far that the aperture stopdown begins to open-up in order to collimate to infinity.
What am I missing? I spent 2-3 hours on this beast yesterday night and got nowhere. |
Alex
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, July 11, 2005 - 04:54 pm: |
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I had a similar problem with the same lens a couple of months ago. There are fourteen, yes fourteen, start points on the helicoids. I ended up taking off the 'rail' on the outer barrel that the guide screw on the inner barrel rides in, and testing each start point individually until things started to line up, then put the rail back on (it's held on by two easily accessible screws). It was a laborious procedure and took me two hours or so to narrow it down to one of three start points, by trying each start point then the adjacent and so on, to see if I could then get the inner and outer barrels to assemble in such a way that the guide screw on the inner barrel end up in roughly the right place. Two of the start points are well out of kilter, and the third (in my case) was eventually easy to recognise, in terms of ending up with the close and infinity focus points being in the right place, then get the rail back on in place. In my case, the helicoids were full of solid grease so it was a clean and re-lube job, followed by a clean of the aperture blades, as they'd become contaminated by migrated grease and were sticking. The aperture blades are controlled by a weak spring whose ends are attached to posts on the inner barrel - I'm sure you'll see them. I'd taken this spring off while I flushed the blades with naptha (lighter fuel), and as I recall, putting it back was the last part of the re-assembly for me. |
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