Repair Sigma Zoom-K 70-210mm (PB mount)

docucat · Joined: 01 Jun 2015 Posts: 7

Hello all, this is my first post here. I have never repaired lenses by myself, but recently I got not bad, but old and fungused Sigma Zoom-K lens (I guess it is same as Prakticar 70-210mm). I am using it with adapter on my canon. Even if there seems to be quite a lot of fungus on several elements, pictures look ok, unless I point to brighter places and with higher aperture, then some stains start appearing.
I tried opening it by myself, but I got stuck soon after I removed back.
I looked a bit and took it together again.
So the reason I am here... have anyone tried opening that lens ? Is it cleanable ? I know it is zoom lens, so it is more complicated than prime.
From what I can say the back glass element cant be taken off after removing metal ring.
I did not want to remove aperture mechanism so as it is not connected to the element anyway, it seems that lens must be opened from front.
I tried taking off the front "beauty ring" but it does not seem to be going off, I do not want to break lens trying.
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There seems to be 2 elements what have fungus on them, second front element and element right in front of aperture blades.
I guess if I could take off black glass element I could access the element what is in fright after aperture...

Anyway, enough talk, there are some pictures of back taken off.
I am sorry, but it is quite dark room and pictures are not perfect .
Fungus (hard to see) :

Lens front(some fungus visible):

Lens back opened:

Some additional images:
http://s3.postimg.org/40n91eteb/IMG_0788.jpg
http://s3.postimg.org/6xaa1oz83/IMG_0792.jpg
http://s3.postimg.org/jneies76b/IMG_0794.jpg
http://s3.postimg.org/56r907hoz/IMG_0795.jpg

Any help ideas will be appreciated, main idea is at least to clean the element right after the aperture blades.