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Philippe Lignieres

Angenieux 12-120mm disassembly

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Hello,
I need to remove the front lens from my 12-1200mm Angenieux to remove the few fungus beginnings that proliferate.
Unfortunately, the first attempts with my spanner were unsuccessful.
Isn't there a reverse thread, at least?
Or is it stuck?
If you have any information, or experience, I'm a taker!

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After further inspection of the problem, the rear lens is also marked by fungus, and finally the front of the mobile unit inside. So I would have to do a complete disassembly. I don't think I'll get by without the full technical documentation. Any idea where I can find that? The mobile group inside seems to be held by return springs, the kind of thing that gets cold in the back...

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Normally I’d advise people unfamiliar with lens service to leave zooms alone, but this is an old junker lens by the sound of it, so could be a good one to practice on. No harm done if it no longer works afterwards!

Production of this lens ceased decades ago so full technical documentation won’t be easy to find. But it probably wouldn’t help anyway - zoom lens cross sections are hard to decode unless you know what you’re looking at and you won’t find a simple step by step guide to disassembly. 

The front element lock-ring won’t be a reverse thread, but it could be secured with lacquer, seized or deformed. Try acetone and gentle heat, and be careful not to slip and scratch the glass. In some zooms the front element is positioned with  8 centering set screws that need to be backed off to remove the glass, and then carefully reset with a lens projector on reassembly. Not an amateur procedure.

An easier way to access under the front element is often to remove the whole front focussing assembly, which also allows for thread relubrication. You need to remove the stop under the outer focus barrel to unscrew the front, and carefully mark everything for reassembly.

With the front off you can also access the front surface of the variator group, part of the moving zoom assemblies.

The rear group is probably best left alone, as there are centering and back focus adjustments that need special tooling to reset.

Sometimes fungus will have etched into the glass and you can only halt the spread. I use a specific fungicide agent no longer available from Zeiss but there are home made recipes on the net.

Good luck!

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I see that this is no small matter and that I will indeed need a little luck to succeed. That being said, I would like this objective to still work "after".  Okay, I'll start at the beginning, and see what happens. I will still ask about the price of a specialist, even if I think it exceeds the value of a 12/120mm... It's a pity, because I'm starting to master the question of polishing the lenses. In any case, a thousand thanks for this vademecum so precise.

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Feel free to post pictures and ask questions as you go. I'll try to help if I can.

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