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Nikon 300/2.8 Ai-s stuck diaphragm
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PostPosted: Tue Mar 31, 2020 5:01 pm    Post subject: Nikon 300/2.8 Ai-s stuck diaphragm Reply with quote

Last year I acquired a Nikon 300/2.8 Ai-s with a stuck diaphragm. Wide open.
I can see a small spring with a bolt hanging down there.
I tried to open it up from the mount but after I removed the mount I stopped because I didn't see any possibility to go further.
Anyone with some experience in dismantling one of those? I know it's far fetched but I had to ask.





PostPosted: Tue Mar 31, 2020 9:56 pm    Post subject: Reply with quote

This lens has internal focusing, right?

I was told some years ago, after buying a Canon 400mm with IF and inquiring about getting into the interior to remove some light fungus, that trying to get into any section of the lens in which the IF system was employed would destroy its calibration, requiring special gear to recalibrate the lens. So, I dropped the idea and just chose to live with the few spiderwebs of fungus.

So, that's the short answer. These lenses -- and I'm assuming that Nikon employs a similar mechanism -- require special equipment to dial in the focus during assembly and if you manage to dismantle any of these areas you will have disabled the lens's ability to focus at all. So, my recommendation is that you leave this repair to the professionals. It's a valuable enough lens where the cost of the repair will be worth it, I'm thinking.

On the other hand, if your 300/2.8 is NOT IF, well . . . I dunno. I would have followed your steps and approached from the rear, since that's where the aperture linkage ends up.


PostPosted: Tue Mar 31, 2020 10:06 pm    Post subject: Reply with quote

Screws under focus ring rubber?


PostPosted: Wed Apr 01, 2020 3:23 am    Post subject: Reply with quote

Cooltouch - it is internal focus

Visualopsins - I'll look at it tomorrow.

Here is a link for the famous Nikon 300mm f/2.0 EDIF. I thought it was the same but I couldn't find the screws

http://www.company7.com/library/nikon/Nikon_0300f2.html


PostPosted: Wed Apr 01, 2020 6:16 pm    Post subject: Reply with quote

I cannot remove the focusing ring.
Under it there is a port hole and through it I can access 2 screws.
But, I take Michael's word and I'll wait for the stores to open.
In the mean time I shoot wide open.



PostPosted: Thu Apr 02, 2020 4:14 pm    Post subject: Reply with quote

Yeah, that's what I'd do. Heck, it's most fun shooting a 300/2.8 wide open, anyway, isn't it? Cool


PostPosted: Fri Apr 03, 2020 2:54 pm    Post subject: Reply with quote

cooltouch wrote:
Yeah, that's what I'd do. Heck, it's most fun shooting a 300/2.8 wide open, anyway, isn't it? Cool


Lots of light