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Canon FL 200mm f/3.5 (breech lock, first version)
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PostPosted: Sun Jan 12, 2020 7:50 pm    Post subject: Canon FL 200mm f/3.5 (breech lock, first version) Reply with quote

Hi, does anyone know how to get inside the first version of the Canon 200mm f/3.5 FL-mount (not the newer version with the built-in hood)? It looks like the front element(s) are accessed from the back since I can see notches for a lens spanner, and as far as I can tell the actual mount is part of the rear barrel (i.e. not removable). I can get the rectangular window off the back, but that still leaves a very narrow opening for reaching inside.

Here's the whole body:


Front element, with an arrow indicating where I think the spanner would be used:


...and the mount; you can see the plate with the rectangular window which I can remove:


PostPosted: Mon Jan 13, 2020 12:14 am    Post subject: Reply with quote

Ah ha! It's screws that seem related to the aperture linkage that stop the helicoids from over-rotating. They keep the front and back locked in the same orientation. Once they're removed, the barrels can be separated. Pictures to come later.


PostPosted: Sat Jan 18, 2020 12:31 am    Post subject: Reply with quote

Separating the barrels still did not give me access to the front lens elements; I suspect I need better tools to unscrew the front. However, I was able to clean the aperture blades enough to restore full functionality from just the rear. My motivation was to 1) repair the aperture mechanism, which was stuck full-open, and 2) clean dirty lens elements as possible.

The two screws at 12:00 and 1:00 hold a simple sliding mechanism that keep the front and rear barrels aligned as you focus:

Disconnecting this allows you to rotate the rear barrel past infinity until it comes off.

From this point, the aperture mechanism could be manually operated. The elements immediately behind the aperture were also dirty.


Very dirty.


For the next 3 photos, note the position of the lever at the bottom...
Wide open:


Partially closed:


Fully stopped down:


I was able to clean the exposed side of the aperture blades with lighter fluid. Operating the aperture while it was wet also mostly cleaned off the unreachable side of the blades. Now that it's clean, a spring in this component keeps the aperture fully stopped down unless you overpower the spring by pushing the lever.


These two photos show how the aperture lever in the mount transmits the open/control actions to the aperture mechamism itself. There's another spring here which overpowers the previously-mentioned spring by default, holding the aperture open until the camera stops down.



...and here the aperture can be operated from the mount:


Tools used and the lens in pieces (including disassembly of the aperture click mechanism, not shown in detail above):