Disassemble Yashica ML 80-200

Welcome to the forum, fx3 ...

A question comes to mind... does the fungus render the lens unusable at any level? I ask that in particular, as the severity and location of the fungus may lead to some alternatives that may not require a complete teardown. Anytime I've encountered fungus issues with zooms (of any manufacturer), the greater complexity of disassembly/reassembly on most of them is orders of magnitude above what it takes to do the same on primes.

Fungus can be UV treated to at least slow it to a crawl, if not stop it's growth outright. If it's small or at a lens' edge where it doesn't affect image quality, that might be a better option. If it's a long-term fungus and it's etched into the glass, no amount of cleaning will help, so the only alternative is replacing entire optical blocks with repair assemblies or parts from donor lenses. That may not be an easy route to go, but it might mean less disassembly.

However... there are some instances where some zooms can be user cleaned without running into optical alignment issues. I don't know if the ML 80-200mm is one of them, and not one I've attempted to open. The ML 28-85mm is fairly easy to do, and the ML 35-150mm is similar in construction. I created a visual 'how-to' on cleaning haze from a 28-85mm that may help if you're still wanting to attempt a fix. I don't think I've ever run across repair guides or assembly charts for any Yashica (or Contax) SLR lenses, but some other members may have created their own or may have experience with the ML 80-200mm and can offer details.

If the fungus is localized to the extreme edge, then there's a good chance that it may not cause issues with images, and UV could be all that's needed. I take fungus on lenses serious enough that I don't cross-contaminate anything by storing them with others that aren't affected, but as quickly as I can, I also do a prolonged UV treatment to do whatever I can to cease any further growth and kill whatever's there. It's an extremely easy process to just set up the lens for prolonged exposure and let it sit and do what it needs to do. I've seen several recommendations on various forums and blogs that some use sunlight to do the work, but I'm not a fan of uncontrolled exposure.

Long ago I bought a couple of UV-C germicidal bulbs in a T8 sized fluorescent bulb, and got a small non-UV light kit to accept the lamps,. It was already wired and had a switch in the case, so that made it truly plug-n-play with the addition of some aluminum foil as a containing reflector. This was before the pandemic and the big rush to LED's, so I think my total cost was under $20 USD for everything. It's more than paid for itself over the years, and is a breeze to use.

On using an infected lens on a clean body... I'll assume that the fungus is internal, and contained between the lens elements and/or optical blocks. Although there might be a slim chance that contamination might occur, I think the environment could be the deciding factor, and how long the lens is mounted. Spores/mold would need both moisture and darkness to grow, so it might be an issue if the lens is in a closet of a non air-conditioned residence in the Mississippi Bayous, but much less an issue on a sunlit shelf in a Michigan living room. A test mount might not cause a problem, but waiting until it's been hit with UV-C over the course of a few days might be the best bet if the fungus is extra heavy, very active, and/or on external elements that haven't been treated.

My usual routine with every lens I acquire - no matter where or whom it comes from - is for it to get an immediate 'bath' after leaving it's package. I use ordinary 3% topical Hydrogen Peroxide (germ/mold treatment) on cotton swabs with paper 'sticks' to go over the outer elements at least twice. Then comes the same treatment with 90% Iso Alcohol (disinfectant), until there are no further streaks seen after it dries. That is followed by at least one more round of RoR (basically, an Ammonia solution) to get any remaining oils off, and then 'buffed' with another clean cotton swab.

I'll take the opportunity to jot down some particulars for later reference,  if anyone stumbles across this and wants to do the same...

UV-C is within the 100-280 nm range of emitted light, where germicidal action is maximized at 265 nm, so the lamp should be certified for the correct range to actually work. There are several bulbs in various base types available to use, but I'd caution against some of the 'UV treatment kits' that are prepackaged at a way-too-cheap price these days. Buyers may not get what they expect, in either effectiveness or durability. I'd stick with well known brands like Phillips for the bulbs themselves - like this one in a T5 size - and get whatever power and holder fits to the chosen bulb. For safe use, here's the UV-C guidelines.

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