Author Topic: 300mm f/2.8 AIS Disassembly Help  (Read 1217 times)

Jack Dahlgren

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300mm f/2.8 AIS Disassembly Help
« on: October 10, 2018, 19:59:31 »
I just bought this without a careful look and now I'm trying to figure out how I'm going to clean up the front element.
Does anyone have any experience in removing the front element for cleaning?

It looks like I need a very large lens spanner but am hoping someone may have done this before and can relate their experience.
I have no lens spanner, so will probably have to make or buy one. If it were not a glass lens I'd just use a punch and tap it out with a hammer, but I hesitate to shock the lens like that.

Hazing

Nasos Kosmas

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Re: 300mm f/2.8 AIS Disassembly Help
« Reply #1 on: October 10, 2018, 20:55:44 »
I can’t speak about 300/2.8 but I did the same job on my 200/4 with my old vernier caliper, just be patient

Jack Dahlgren

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Re: 300mm f/2.8 AIS Disassembly Help
« Reply #2 on: October 10, 2018, 21:20:40 »
I can’t speak about 300/2.8 but I did the same job on my 200/4 with my old vernier caliper, just be patient

Did you use anything to loosen/lubricate the threads?

Nasos Kosmas

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Re: 300mm f/2.8 AIS Disassembly Help
« Reply #3 on: October 10, 2018, 22:03:22 »
I used some drops of acetone in case of glue present in the threads, I followed Richards recommendation-richardhow.com

Jack Dahlgren

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Re: 300mm f/2.8 AIS Disassembly Help
« Reply #4 on: October 10, 2018, 22:13:07 »
I used some drops of acetone in case of glue present in the threads, I followed Richards recommendation-richardhow.com

Richard is the best. I'm visiting Tokyo at the end of the year, maybe I should visit him with it...

Seapy

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Re: 300mm f/2.8 AIS Disassembly Help
« Reply #5 on: October 10, 2018, 22:26:50 »
When I bought my 300 f/2.8 AIS I found the iris was damaged, A company in Norfolk 'serviced' it for me and replaced two or three iris blades their charge was very modest.  Sadly they were unable to unscrew the original Nikon UV filter and had to break it to get it off.  Since then it has done me good service although I think it would benefit from cleaning, but if you only have small debris on the inside of the front element I wouldn't worry.  I put my hand in front of mine this afternoon and I could still see the subject almost un-impeded!
Robert C. P.
South Cumbria, UK

Jack Dahlgren

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Re: 300mm f/2.8 AIS Disassembly Help
« Reply #6 on: October 11, 2018, 01:37:53 »
When I bought my 300 f/2.8 AIS I found the iris was damaged, A company in Norfolk 'serviced' it for me and replaced two or three iris blades their charge was very modest.  Sadly they were unable to unscrew the original Nikon UV filter and had to break it to get it off.  Since then it has done me good service although I think it would benefit from cleaning, but if you only have small debris on the inside of the front element I wouldn't worry.  I put my hand in front of mine this afternoon and I could still see the subject almost un-impeded!

I added a photo. Seems like a bit more than a small amount of debris so I will want to clean it. Fortunately no filter on the front.

richardHaw

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Re: 300mm f/2.8 AIS Disassembly Help
« Reply #7 on: October 11, 2018, 02:17:59 »
that front retainer ring is sealed with lacquer/enamel.

to break the seal:

use a very sharp knife and scour the seam to break the paint on the seams.

put a drop of alcohol on the seams, let it work on the seams. repeat doing this for a few hours.

if you dont have a spanner bug enough you will have to make one yourself.

i have serviced monster zooms before and I almost always had to make my own spanners from pieces of metal.

in the factory they used a HUGE pipe key mounted on a vise to tighten or loosen these. I have seen them myself. :o :o :o

CS

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Re: 300mm f/2.8 AIS Disassembly Help
« Reply #8 on: October 11, 2018, 02:28:31 »
Richard is the best. I'm visiting Tokyo at the end of the year, maybe I should visit him with it...

That would appeal to me because Richard has the experience, where I don't. YMMV
Carl

richardHaw

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Re: 300mm f/2.8 AIS Disassembly Help
« Reply #9 on: October 11, 2018, 02:30:08 »
Richard is the best. I'm visiting Tokyo at the end of the year, maybe I should visit him with it...

not the best! lol. let me return the favor from last time, i will treat you and your daughter to my favorite restaurant. its the best

well, i can give it a try if you want but no guarantees. :o :o :o

Seapy

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Re: 300mm f/2.8 AIS Disassembly Help
« Reply #10 on: October 11, 2018, 08:46:00 »
I just looked at mine (Serial 605808).  Where the lens hood slides back, near the back of where the retracted lens hood goes, there are three very small screws which appear to either retain or lock the front part of the lens to the main body.  I would guess they need slackening or removing before the front will screw off.  I can't see any engagement slots or holes for a peg spanner to unscrew the front part of the lens.  I would expect some sort of strap wrench, if indeed it does unscrew.
Robert C. P.
South Cumbria, UK

Erik Lund

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Re: 300mm f/2.8 AIS Disassembly Help
« Reply #11 on: October 11, 2018, 09:37:46 »
Why does it need cleaning? Dust specs has no influence on images.


Opening up such lenses is not recommended unless you know exactly what and how,,,
Erik Lund

Jack Dahlgren

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Re: 300mm f/2.8 AIS Disassembly Help
« Reply #12 on: October 11, 2018, 19:46:36 »
Why does it need cleaning? Dust specs has no influence on images.


Opening up such lenses is not recommended unless you know exactly what and how,,,

Eric,

If you could take a careful look at the fogging along the left side and let me know what your opinion on this lens is I'd appreciate it.

To me it looks more extreme than just dust specs. I don't have the lens in hand yet, but I see what looks like an odd finger print and fungus along that edge.

If the front element is not too difficult to remove and wipe down I will do it.
I'm generally able to figure out how to take things apart and put them back together again and have opened a couple of old Nikkors to clean and lubricate them, so removing a retaining ring is not something I consider high risk even if I have not done it on this size lens before. The lens was rather inexpensive so financial risk is low too.

Arteemo

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Re: 300mm f/2.8 AIS Disassembly Help
« Reply #13 on: May 15, 2020, 15:25:03 »
Can I ask, did you ever fix this issue? I have the same lens with the same issue & I can’t get the front element off. Any ideas would be much appreciated. I’m desperate to clean it properly & use it on my recently purchased F4.

Jack Dahlgren

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Re: 300mm f/2.8 AIS Disassembly Help
« Reply #14 on: May 15, 2020, 16:10:45 »
Can I ask, did you ever fix this issue? I have the same lens with the same issue & I can’t get the front element off. Any ideas would be much appreciated. I’m desperate to clean it properly & use it on my recently purchased F4.

As is often the case, my attention shifted to other problems. I've been using the lens happily as it is.