Any clue how to disassembly front element from Contax 100/2?

[Giovanni]

Long story short,
I have a bunch of CY lenses from Germany, among them a couple got fungus, the 50/1.7 and 100/2 have very slight traces on the back of the front element, I got the rubber circles to unscrew the front element, I started off the 100/2 as I want to take it with me for a trip but found out that it is a block along with another element and dunno how to unscrew just the front one off the combo, any clue how to try that?

I am waiting to get isopropyl alcool to try and clean it, also have to buy gloves and eventually a market to paint the borders in black as recommended by some tutorials, still if I handle to tear it apart...

The traces of fungus are very very light but I am afraid it will spread and I have tree more lenses who got it, one of them was sent to Nikon very long time ago, they charged a lot and the problem is back so I rather try it myself, nothing to loose on these old lenses and too expensive to send them to a repair (which I did with the Distagon 35/1.4 and Planar 85/1.4).

Thanks for your attention

Giovanni

[kiddo]

Unless having good knowledge on repairing lenses ,I wouldn't learn on a Zeiss 100mm D2 , that's still an expensive lens nowadays ,just like the other mentioned that you have

[caspert79]

If the fungus is there already for a long time, I’m pretty sure it’s dead. I would store it in a non-humid environment.

[kiddo]

do you have pic of how far have you reached to open it? if you already got front group removed, than you might have to deal with some kind of loctite (in yashica ML red one, the worst, but it would work with acetone after multiple attempts) - don´t know if it would be the case for your lens, but as far as i know, some of these blocks (groups) might have a retaining screw, others are glue sealed (loctite or not), others might use some retainers that are visible and worse ones would be the one in a capsule (minolta zoom 35-70mm macro but most of the cases only 2 elements)- i might be missing some other op`tions though -