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Username: Woodsy

Post Number: 1
Registered: 03-2011
Posted on Friday, March 25, 2011 - 07:42 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Hi,I have a problem with an original Canon F-1. The lever inside the camera body, that gets pushed down by the lens coupling lever when the aperture is closed down, gets stuck when the aperture is fully closed. This then shows up in the exposure meter, as the aperture needle stays at the top. It can be unstuck by pressing the stop-down lever, or by removing the lens and gently moving the lever. It's not very 'sticky' so can be moved quite easily. Any ideas how this can be fixed please?
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Username: Brcamera

Post Number: 76
Registered: 08-2010
Posted on Saturday, March 26, 2011 - 12:49 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

This was a common issue with the F-1. The diaphragm sensing lever in the mirror box contacts the lever on the rear of the lens to move the meter pointer in the viewfinder as you change f stops on the lens. The diaphragm sensing lever has a ramp,visible once the mirror box is removed, that contacts the meter pointer lever arm. The meter pointer lever slides on the length of this ramp and when the ramp has any sort of abrasion or wear, the diaphragm sensing lever sticks in the down position. When parts where still available from Canon, I just replaced the whole assembly and that solved the problem (Canon calls the part a Correction Lever Unit, part 18-0475). Since those parts are NLA, the fix that I would now give is to carefully burnish the ramp to make it smooth. I have also applied an almost microscopic layer of dry moly to the ramp. Of course, you have to remove the mirror box to do this fix and depending on your skill/experience level, this can be tricky on the F-1 (very easy to damage the meter pointer).
f1 mirror box

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