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David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 2
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 18, 2009 - 05:40 pm: | 
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The immediate problem that inspires this posting is a Zorki-3M which sometimes misfires on B: one time out of ten or so, it fires as if on a slow "fast" speed (say, 1/25th) instead of staying open until the shutter button is released.
The apparent cause of this is that the second curtain is not "catching" the tang that's supposed to stop it, but instead just zooming on by it. Since this camera has a somewhat chewed-up tang, I'm not sure it that's the problem, or if it has to do with too much or too little tension on that all-important down-and-in spring (anyone who's worked on these SovCams will know what I'm talking about).
That's the immediate problem. In the interest of furthering my knowledge of how these shutters work in general, as well as possibly for other folks, I'm wondering if anyone out there can explain, or has explained, exactly how these shutters work. I've seen plenty of web pages that tell how to work on these Leica-copy shutters, but I've never seen one that satisfactorly explains how they work. Especially the difference between "B" and the instantaneous speeds; it's a mystery to me what makes that speed work, since it's simply another notch on the shutter speed-selection disk.
Any light that some knowledgable person(s) could shed on this would be greatly appreciated. |
Prasanna
Tinkerer
Username: Prasanna
Post Number: 39
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 18, 2009 - 08:16 pm: |
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You may want to read Rick Oleson's site. He has posted details and diagrams on the Zorkis. Just Google Rick Oleson or <www.tripod>. Regards, sp |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 5
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 18, 2009 - 09:08 pm: |
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Thanks; I know Rick, and have emailed him in the past on several occasions. His site is indeed invaluable and a wealth of information, and he's a very generous guy. Unfortunately, he doesn't have what I'm looking for--an explanation of how exactly these shutters work.
By the way, his site is here: http://members.tripod.com/rick_oleson |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 6
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 18, 2009 - 11:45 pm: |
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Well, looking again through Rick's site, I did find this page, which explains how these FED/Zorki shutters work in general. However, it doesn't have the detail I want on how the damned mechanism actually works--how those pawls and catches and stuff do their little dance as they spin around.
Some good pictures would be nice too. |
Harryrag
Tinkerer
Username: Harryrag
Post Number: 150
Registered: 05-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 19, 2009 - 07:16 am: |
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There is also this one http://jay.fedka.com/ Maybe it is of some help. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 1023
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 19, 2009 - 02:54 pm: |
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does this help at all?
http://rick_oleson.tripod.com/leica.pdf |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 8
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 19, 2009 - 07:07 pm: |
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Are you kidding? That's just about exactly what I was looking for. (I think I've seen that somewhere on your site before but forgot about it.)
In case there's any question about it, just remember: You Is Da Man.
Getting back to my original problem (my Zorki-3M that often misfires on B): having read this explanation, it seems the problem is that the 2nd curtain pawl is just blasting on by the release lever which should be catching it. I'm wondering if this has anything to do with the release lever spring tension. (This spring pushes in two directions: down and in. Down seems OK, as the lever rides up and down as the shutter button is pushed.) Is it possible there's not enough inward tension on it? or maybe too much?
Thanks again for this very nice little tutorial. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 1024
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 19, 2009 - 09:27 pm: |
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it might be too weak in the in direction, so the thing just blows it out of the way. also if the pawl is buggered up, it might not have the correct shape at the edge to get a good grip. |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 14
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 21, 2009 - 09:02 pm: |
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Well, turns out that the spring was indeed the cause of the problem. It was too weak pressing in on the release pawl, and after re-bending and replacing it, the camera works reliably on "B". Shows how sensitive these cameras are to the proper tensioning of this crucial spring. |
