stiff diaphragm

[rmolson]

Stiff diaphragm ring

I picked up a Praktina FX I got it for the lens a B Jena 58mmf/2 Which if I am right is the classic 58mm Biotar I had one once before in the olden days with automatic nothing, but a fantastic lens. The lens is a present which means you focus wide open and then manually close down the lens to a present stop The preset ring itself is spring loaded and works fine but the barrel it connects with is very very stiff I am guessing the lube has dried up So while my impatience screams oil it I don’t want to wreak what may be a fine lens . Any suggestions as to remedies or best repair services for old lenses

 

[benjiboy]

Stiff diaphragm ring

I picked up a Praktina FX I got it for the lens a B Jena 58mmf/2 Which if I am right is the classic 58mm Biotar I had one once before in the olden days with automatic nothing, but a fantastic lens. The lens is a present which means you focus wide open and then manually close down the lens to a present stop The preset ring itself is spring loaded and works fine but the barrel it connects with is very very stiff I am guessing the lube has dried up So while my impatience screams oil it I don’t want to wreak what may be a fine lens . Any suggestions as to remedies or best repair services for old lenses

The lens isn't "present", it's pre-set.

 

[John Koehrer]

Never oil. A small drop of rubbing alcohol into the area between the ring & barrel and working it for a few moments may do it. If the alcohol didn't cut it try Coleman lantern fuel(Naptha) A small drop. Dip a sewing needle into the solvent and touch it to the barrel/ring. Use the eye so it picks up that drop. The pointy end doesn't work quite as well.