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Message |
    
Mikeguyver
Tinkerer
Username: Mikeguyver
Post Number: 32
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 25, 2010 - 07:58 am: | 
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Hello,
I have a Carl Zeiss Jenna 2.8/50 silver lens that needs major cleaning. It was sitting out in the open for years-lot of dust on the lens and focusing is stiff. I have searched the web to find any information on disassembling the lens. Your input is appreciated.
Mike |
Mareklew
Tinkerer
Username: Mareklew
Post Number: 200
Registered: 03-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 25, 2010 - 11:22 am: |
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Post a picture, it will be easier to tell which lens it is.
https://kyp.hauslendale.com/classics/forum/messages/2/18443.html
does this one seem similar?
Marek |
Mikeguyver
Tinkerer
Username: Mikeguyver
Post Number: 33
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 26, 2010 - 06:38 pm: |
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Mareklew,
Here are the photos you requested
Mike   |
Steve_s
Tinkerer
Username: Steve_s
Post Number: 174
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, November 28, 2010 - 12:44 am: |
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I have a couple of Exakta mount Tessars which look outwardly the same as yours. Each of mine is constructed slightly differently - see pictures below: -
 
In both cases you start by removing the outer retaining-ring at the back, and the complete optical/aperture assembly, with the focus setting spacer ring, comes out from the front. |
Mareklew
Tinkerer
Username: Mareklew
Post Number: 201
Registered: 03-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, November 29, 2010 - 02:55 am: |
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Mike, this is a different lens than what I have taken apart.
However, most are built on similar principle: you take the mount off, there is some provision for preventing the center block from rotating when focusing - either a long screw, or a pin, or...
You take that off and screw the optical block out of its focusing helix - preferably noting the angle at which it came out (helix is multi-threaded and you can mount it at an offset which will throw the focusing way off).
The optical block can usually be taken apart into main lens groups that are in front and behind the aperture.
In some lenses (i.e. Jupiter 8) the optical block sits in an outer tubus and first that tubus meshes with focusing helical. You can take the optics out without disassembling focusing.
In the first variant, the manufacturing tollerances are often adjusted at the focusing ring (the infinity stop and scale are moved). In the second case the optical block is shimmed.
Marek |
Mikeguyver
Tinkerer
Username: Mikeguyver
Post Number: 34
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, December 01, 2010 - 05:32 am: |
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I have partially disassembled the lens (left the aperture alone). Cleaned and lubed the helix and reassembled the lens. The reassembly took several tries due to focusing helix offset (each time checking the lens at infinity focus till I got it right). Next time to make the reassembly easier I will make a scratch mark on the two helix parts (with the inner ring flush with the outer ring). Now that I have the lens reassembled and mounted on my DSLR (for testing). Focusing is much better but still on the stiff side. The thread on the focusing helix are fine. I used a lubricant that was a little too thick (works better on coarser helix thread). Any suggestion on what lubricant to use on this lens?
Mike |
Prasanna
Tinkerer
Username: Prasanna
Post Number: 60
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 03, 2010 - 07:16 am: |
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Mike, the suggestion on the appropriate lubricant is a bit difficult. Most people would recommend All Purpose Grade 3 grease. It is the same as the Front End Bearing grease for cars. I use the same. However, I have found that in some old lenses this grade AP3 makes it too smooth; the lens keeps shifting position. It is better to try out different grades and arrive at a suitable one. |
Monopix
Tinkerer
Username: Monopix
Post Number: 173
Registered: 11-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 03, 2010 - 07:45 am: |
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I use this for most lenses. There is a thicker version if you prefer it.
http://www.micro-tools.de/en/Greases-Oils/Grease-Helical-10-Light-8ml.html |
