While testing the Kohler System, I dismantle the brightfield condenser and examine it. my first surprise is - it is also made from cheap looking black plastic ! - Who would have thunk that poor Carl Zeiss has decended to such depths of degradation using flimsy Plastic parts on such a microscope.
I further notice I see that the entire body of the condenser is coated with some sticky gooey oily substance. Someone apparently tried to service the condenser and possibly relubed it- but the job was very sloppy and lots of the oil has gotten on the outside and made the entire lower part of the condenser sticky. On top of this sloppy job, When I checked out the iris control lever I noticed that the lever used to control iris aperture is seriously bent and the thin metal part defining the upper side of the slot within which the lever moves is bent upwards in the middle part. This caused the iris leaves to pucker up at the end of the lever's travel (the end which minimizes aperture). When the lever was moved to that position, the entire iris stopped being flat and planar and developed a concave shape like a small volcano cone !
I managed to fixe this somehow by bending the renegade bent part back into shape, and straitening the flimsy thin lever (Guess what ?? the lever was made from metal but was very thin and is very easily bent) which resulted in restoring the proper planar shape of the iris even at minimum aperture.
However, It is exactly after fixing this problem and seeing how cheaply engineered and badly executed this plastic condenser is, that it dawned on me "this is not your father's Carl Zeiss !"
Having said that, I looked at the back side of the microscope. Here's a picture of it