Flektogon 50mm f4 aperture opens but doesn't close

Alexander6x6 said:

Once you have fixed it, it is essential to always keep the lens with the closed (f22) aperture.

Click to expand...

blee1996 said:

This is a common problem with Pentacon Six lenses, that lubricant migrated to the aperture blades which made them stick together. Out of 5 Pentacon lenses I bought, 3 need service. Including one Flektogon 50/4.

Initially I just removed both front and back lens groups (quite easy), and wipe the blades as clean as possible using lighter fluid. This is the quick and dirty solution. It worked for a couple of days or weeks, and soon the blades are struck again.

Eventually I have to do a full disassembly, taking out all the aperture blades and associated mechanism, and thoroughly clean everything. And they are still working properly today. However, you need lots of patience and time to do the full service yourself. It is not super difficult if you had some experience and the right tools. The lens construction is not complicated if you take lots of photos along the way, but putting the aperture blades back together can be quite frustrating.

Click to expand...

Yobo57 said:

Thanks for the reply. Do you know which of the four rings I should loosen to remove the rear lens group?

Click to expand...

blee1996 said:

I believe it is the yellow ring.

But in my case, I have the MC version which might be slightly different from yours mechanically. In addition, I removed the mount and aperture ring (be careful with tiny ball bearing and spring for aperture click stops) as well.

Also if you can remove the front group, that might be better since you can access the aperture blades from both sides. It only needs a friction cup to remove the beauty ring (where there is the lens name) first, and then the slotted wrench can get the whole front group off.

Click to expand...