Few days ago, when shooting a patient (I mean photographing
) I noticed that the manual focus ring wasn't working when focusing from near to far; from far to near was OK.
So, after work I began to disassemble the lens. Step by step, and studying every move I made, kind of figured out the problem.
Whenever you remove the rubber ring there are 3 screws holding an outer cup-like collar responsible for manual focus.
Removed it after unscrewing them.
Without the collar manually focusing was OK.
Putting back the collar, MF was again working.
But whenever attaching the screws... it doesn't focus from near distance to far.
BTW, the screws get inside 3 oval windows on that plastic collar, and have a tiny distance to "wobble" in it. The collar has 3 drawer like places where 3 nail-like metals get in, and when turning the collar to either direction, the nails incline to one side grasping the real focusing rail inside.
So, obviously, the nails were inclining on one side but not to the other.
Therefore, I deepened the oval windows on one side et VOILA!
Now it works as new.