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Message |
    
Aphototaker
Tinkerer
Username: Aphototaker
Post Number: 35
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 03, 2010 - 09:00 am: | 
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Hello.
I am trying to take out the aperture diaphragm unit from a Canon fd 50mm f/1.8 S. C. lens.
I have unscrewed the name ring, then removed three screws to take out the second ring and now I am at the third step and not sure how to proceed further. I am attaching the photos of these steps I have done
My objective to see what is wrong with the diaphragm. Working the aperture does not move the blades in the lens. If it is sticky aperture, I can just douse it in naptha. And if it is just missing that piece altogether ..... oh well.
The photo above shows the unscrewed name ring of the lens.
The photo above shows the second ring taken out by unscrewing the three screws.
Now I am left with this. The next three screws appear to be keeping the focusing ring in place. The cylinder housing the lens does not appear to be unscrewable. What do I do next?
Thanks. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 1032
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 03, 2010 - 11:13 am: |
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I have never worked on this specific lens. On the f/1.4 SSC, which appears to be very similar in construction, this lens cell unscrews. Removing the focus ring may give you a little better access to get a grip but should not be necessary. In the later bayonet-mount f/1.8, the lens cell lifts out without unscrewing, but that lens is quite different in construction.
If you haven't already come across it, I have some sketches on the f/1.4 here which may be of interest: http://rick_oleson.tripod.com/index-161.html |
Aphototaker
Tinkerer
Username: Aphototaker
Post Number: 36
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 03, 2010 - 11:26 am: |
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Hi, Rick. I have gone over your sketches, which is in itself quite nice and instructive work. Now that I have mentioned it, I also want to thank you for the drawings as a great help to all people interested in lens repair.
Well, however hard I may try, I am not able to budge the lens cell.
I was thinking of removing the three screws shown in the third photo in my earlier post in this thread. However, one of the screws is very tight and I am afraid I have damaged its head a bit (tried various kinds of screw drivers, even filed one to fit right in to the screw head). I have left those screws alone for now, fearing I may damage the screw head ever further.
Any suggestion on making that lens unit yield?
Thanks. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 1033
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 03, 2010 - 06:26 pm: |
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No... without having worked on that particular lens, I'm afraid to suggest something that might cause damage. I believe that cell should unscrew, but that could be incorrect - this lens appears to have more plastic in it than the f/1.4 did, and that might mean a different assembly method. Removing the focus ring may reveal some hints. |
Aphototaker
Tinkerer
Username: Aphototaker
Post Number: 38
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 03, 2010 - 06:44 pm: |
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Okay.
I have to first find out how to go about opening that stuck screw. That would allow me to remove the focusing ring.
I wish I could cut a slot across the screw head to use a bigger driver, but there is no space to work around there.
Thanks. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 1034
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, January 04, 2010 - 07:03 pm: |
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I don't know what you've used as a tool to try to unscrew the cell. I have found the usual "rubber stopper" tools often do not have a good enough grip to loosen a tight thread. The most successful alternative that I've found is double-sided foam adhesive tape. Apply this, either instead of rubber sheet onto the end of a piece of plastic pipe, or onto the face of a rubber tool; press it firmly against the stuck part and twist as you would a rubber tool. The adhesive gives it a much stronger grip, and requires less axial force as you twist. |
Glenn
Tinkerer
Username: Glenn
Post Number: 732
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 05, 2010 - 08:07 am: |
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Square off the tip on a small electric soldering iron and apply the heated tip to the screw head. The steel screw is 'corroded' into the alloy barrel - the barrel being alloy will expand more than the steel screw and thus you will be able to remove said screw with a well fitting screwdriver. Use driver immediately after removing heat source, do not allow to cool down.
Used this method many times on items ranging from photographic equipment to vintage bike and car engines - never fails if the correct sized heat source is used. |
Aphototaker
Tinkerer
Username: Aphototaker
Post Number: 41
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 05, 2010 - 08:24 am: |
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Glenn, that seems to be an interesting idea. Looks promising. I will try that out as soon as I get some time this week. I will, of course, report back what happens.
Thanks. |
Helgen
Tinkerer
Username: Helgen
Post Number: 1
Registered: 05-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 18, 2010 - 04:01 am: |
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Can somebody PLEASE tell me how to get that name ring off!? I tried the tape method, tried rubber... I can't get it off my FD 50mm lens! (Mold in lens.) |
Glenn
Tinkerer
Username: Glenn
Post Number: 778
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 18, 2010 - 04:33 am: |
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Are you talking about the Breech or nFD lens? The nFD ring is just glued in - make a thin lever and protecting front element with a pad of lens cloth insert lever between inner diameter and element, then gently lever out. On the breech lens run some naphtha round the threads and leave for a while before using a piece of thick walled plastic pipe with double sided tape wrapped around the end. If this does not work apply some heat to the filter ring before attempting to unscrew. Tip for applying heat - wrap a couple of turns of heavy gauge copper wire around filter mount, twist the two ends into a tail about 2"-3" inches long and then gently heat the tail with a soldering iron or small gas torch. You will find the most stubborn rings easily spin free using this method of even heat distribution |
