1. Disassembly
The handle on the aperture ring (red circle) is often stuck fast. This is due to old grease from the USSR that has hardened. The solvents have evaporated, leaving behind a tallow-like hard mass.
Since we will also be cleaning the lenses, we first remove the ring that holds the front lens in place using a spanner (see green arrows). The front lens can usually be removed easily; if necessary, a small rubber suction cup can help.
Remove the light trap (left). It can sometimes be quite tight. The fit can be adjusted using the 3 bendable tabs.
Unscrew the rear lens block using a spanner (bottom left).
Now remove the inner ring using a spanner (bottom). It holds the housing with the aperture blades in place. The ring can be quite tight.
The tube, front ring, and aperture diaphragm housing must be removed.
This grub screw must now be removed. It holds the aperture blade housing in the correct position (left).
There is a tiny screw (marked in red) under the hole in the front ring. It holds the front ring in the correct position. It is often covered by a piece of felt (bottom left).
After unscrewing the front ring, you will see the aperture blade housing with the inner lens. One or more shims may fall out of the tube.
The aperture grip is attached to the aperture blade housing with two screws. Unscrew these and remove the silver ring with the grip (below).
2. Cleaning
The remains of the former lubricant now consist only of hardened tallow. It must be removed, including from the recessed slots. The two screws run in these slots, thus limiting the aperture setting (left).
The silver ring with the handle must also be cleaned inside and out.
All cleaned parts below: light trap, rear lens block, aperture housing mounting ring, front lens ring, front lens (from left to right, top). Focus unit (see here for cleaning instructions), tube, aperture housing, ring with aperture handle, front ring (from left to right, bottom).
The green arrow marks the middle lens, which can also be unscrewed. This gives you direct access to the exposed aperture blades.
3. Lubrication and assembly
Apply a sufficient amount of grease to the aperture diaphragm housing. Then replace the ring with the handle and secure it with the two screws. The aperture should now be able to be adjusted smoothly again. Mark the position where the grub screw goes in at the bottom of the ring. This makes installation easier (left).
Now push the aperture blade housing through the front ring and reinsert the shims into the tube (below).
Now push the parts back together and make sure that the grub screw can be tightened again in exactly the same position as before (bottom left).
Finally, reinsert and secure the cleaned front lens, and voila!
