asherang

I have written a blog on the disassembly of a Canon 50mm f/1.8 FD SC (with notes on 50mm f/1.4 FD SSC). In the introductory section there are lots of instructions on the breech lock Canon mount. Look through that and you should be able to get your mount back together. Things to note when lifting up the breech lock mount: (1) The AR coupler – the almost dark metal piece at 270⁰. This AR coupler would move with the AR, and is an important piece to reinstall the aperture ring detent ball bearings. Exact position of this coupler must be noted for correct setting of aperture as well as constraining the ASL to the correct position (previous photo). (2) Aperture curve – that controls the size of the aperture when the coupler moves with the ASL (pulled by the very long spring in the previous picture, but constrained by the AR coupler; so complex 3-piece movement with a spring!). In the method I disassemble the lens, the aperture is set at maximum, which corresponds to the flat part of the aperture curve. (3) At 100⁰ on the inner collar the EE switch pin sits. When the AR moves the metal strip on the outer collar moves, and towards the end at the minimum aperture the strip has a bump and pushes the EE switch pin up and thus will only allow the lens to be set to O or A when the camera has a corresponding hole to allow the EE switch pin to sit in. At this time remove and keep the EE switch pin save. Or it may launch itself on the crevice on the floor and defy the most ardent search party conducted to find Hope this helps.