u/DenKHK

Dear all, I picked up a beat-up Olympus F.Zuiko 50mm f/1.8 lens to practice CLA and restoration on. It's an older silver-nose model (Pic 1).

I have 3 questions I would like to seek your help on, from easiest to most difficult.

1. On the back plate (Pic 2) there is a tiny peg sticking out, circled in the photo. The peg dropped out of this lens (Pic 3). However, I cannot see what function it serves, since it seems to be connected to nothing on the inside of the plate, just plugged into a hole in the backplate (Pic 4). I have however seen this peg in other zuikos of similar generation but not the later ones. Does anyone know what it's for?

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2. The lens had quite some fungus both on the glass and even on the body interior. The rear optical unit had some on its body as well (Pic 5). I managed to clean most of it off with hydrogen peroxide-ammonia mix, but there's still some white stuff left (Pic 6). I have not been able to clean it completely even with cotton buds and fine paintbrushes, and because it's a sealed unit, I am reluctant to just soak it in the peroxide mix. What other ways can I try to get rid of it, or is it just dead fungus and ok to leave it there?

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3. On all the parts diagrams and videos I have seen on disassembling this lens model, after removing the name ring and the filter ring the front element can be removed as a single unit by unscrewing it out with a lens wrench. However, my unit is different - there are no notches or holes for a lens wrench on the front element. Instead, a front ring unscrews off, followed by 2 layers of bare optical lens (with a retaining ring on the inner one). What I am left with is what might be analogous to the body of a front element in the lens barrel (pic 7).

Problem: I can't get that element body out. Again, no holes or slots/notches for a wrench, and wouldn't unscrew out even with rubber lens tools.

After some searching I found a parts diagram for this lens, which appears to be a Type 1 version of this model, and I've added an excerpt of the parts diagram with the stuck unit marked with an arrow.

I have tried dripping at different times IPA, acetone and WD 40 along the edge of the unit, but the unit it still completely stuck. I would really appreciate any help or advise on what else I can try, especially if you have encountered such strongly-glued lens before!

Thank you all in advance and apologies for the long post!