The aperture blades on my Kaleinar-3b 150mm f2.8 lens for the Pentacon Six were rather sticky, so what to do? I had never opened up a lens before, but I figured this could be the perfect lens to rehearse on. Seeing that the aperture is sitting close to the bayonet of the lens I decided to start from the back. Three screws removed and the back cap came off. But when I lifted it out, two broken bits of a brass coloured washer fell out, see the second picture. Not very nice! I proceeded to unscrew the rear lens element, it can be done just using your fingers. And there they were, the bronze coloured aperture blades. I dared not go further in, so I cleaned them in situ with lighter fluid and brushed them with a tiny amount of graphite dust. When I reassembled I just left the broken bits out. The aperture and focus rings run smoothly so I believe it's ok.