Repair and disassembly guides for SLR, DSLR, and mirrorless interchangeable camera lenses.

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Disassemble front element of Ricoh Auto Rikenon 400mm F6.3 Lens

I've got a fungal growth inside of the front element.

I have read the cleaning answers given, and am quite prepared to undertake it. However the sealing ring does not have any holes on/in it (just writing) for a lens spanner, consequently there is nothing to get a grip on and have failed in all my attempts to unscrew it. This of course this means I can not remove the front lens so as to access the fungus in behind.

My question: How do I remove this sealing ring ?

P.S It is definitely screwed in - I think.

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Hi @sam13 ,

Just wondering it it is meant to be unscrewed in a clockwise direction and not counter clockwise.


There is a thread visible and I have doubled checked it and it is clearly normal ie unscrew counter clockwise. Of coarse I am assuming that the ring is in fact screwed in via this thread and not pressed in. That just doesn't seem right.

Its got to be just well and truly stuck onto that thread. But the thing is, I cant move it as I have no way to grip it. I am very reluctant to spray anything like WD40 to loosen it up as I think that will seep inside and bugger-up all the lens.

My alternative solution is to allow sunlight ie uv rays to burn the fungus off. Trouble is there is three patches of fungus and I think unless I can get in and clean them off there will be residue left and the lens will continue to be compromised.

PS Still looking on the internet but cant find any manual.


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1 Answer

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You'll need to get a rubber stopper used to seal bottles. Review this chart: Rubber Stopper Size Chart to figure out what would be the ideal size. You'll also need to modify it as the center part of the stopper needs to be ground down so it does not touch the lens as the filler in the stopper is abrasive and will scratch the lens. I've used a Dremel Tool. I find the stoppers with the center hole are easier to hollow out as the hole offers a good reference and starting point.

Once you've made the tool you'll just press down on it just enough for it not to slip and then turn. Don't press to hard as you don't want to bind the threads

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That sounds brilliant. And so simple. Thank you I'll definitely try it


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