|Posted: Sat Jan 18, 2020 12:31 am Post subject:
|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.
For the next 3 photos, note the position of the lever at the bottom...
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):