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Repairing a Sigma 70-210 f/2.8

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beeton View Drop Down
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Post Options Post Options   Quote beeton Quote  Post ReplyReply Direct Link To This Post Posted: 27 January 2020 at 12:55
Rear group.... if I recall other similar lenses, 4 silver screws for mount, 3 small black ones for shroud, 2 slightly large black ones for contacts, rear cell should unscrew. They may have used locktite type products on the threads. Send a picture if you have one.
 



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neilt3 View Drop Down
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Post Options Post Options   Quote neilt3 Quote  Post ReplyReply Direct Link To This Post Posted: 27 January 2020 at 23:29
Originally posted by beeton beeton wrote:

Rear group.... if I recall other similar lenses, 4 silver screws for mount, 3 small black ones for shroud, 2 slightly large black ones for contacts, rear cell should unscrew. They may have used locktite type products on the threads. Send a picture if you have one.


I've no pictures to hand , that's if I took any .
When I get chance I will dig the lens out and post some to i.d it , as well as stripping some of it down again to have another look at it .

The rear lens group has haze , hopefully just a layer on the innermost parts that will clean up , and not between two cemented pieces .
see my photostream on flickr;
http://www.flickr.com/photos/neilt3/
C & C welcome.
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Osi View Drop Down
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Post Options Post Options   Quote Osi Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2020 at 12:29
Originally posted by neilt3 neilt3 wrote:

Originally posted by beeton beeton wrote:

Rear group.... if I recall other similar lenses, 4 silver screws for mount, 3 small black ones for shroud, 2 slightly large black ones for contacts, rear cell should unscrew. They may have used locktite type products on the threads. Send a picture if you have one.


I've no pictures to hand , that's if I took any .
When I get chance I will dig the lens out and post some to i.d it , as well as stripping some of it down again to have another look at it .

The rear lens group has haze , hopefully just a layer on the innermost parts that will clean up , and not between two cemented pieces .


God! How powerful the internet is. Well, I hope I'm doing this right and poster can see my message. Being an old lens, I didn't bother to check online for assistance but after two days battling this rear lens group, I decided to give it a try. Let me assure you I have 100% the same problem and SADLY, the haze is not accessible (at least yet) and that's why I'm here. The haze is between the two exposed sides of the very last set of elements and I've exhausted all the tricks I have trying to extract the elements from the housing to no avail. It looks like they're sealed together but I saw no tell tale signs of Balsam separation. The haze is so bad I could not convince myself it was made that way. It cuts as much as a third or half of the light through it! Anybody with any clue? I'm a very experienced and competent amateur self-taught repaired of these things and I got this far in the disassembly process only to get stuck here. Heeeeeeelp!
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Osi View Drop Down
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Post Options Post Options   Quote Osi Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2020 at 12:32
I would have liked to attach a photo, but have found no way to do it
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neilt3 View Drop Down
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Post Options Post Options   Quote neilt3 Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2020 at 12:42
To post a photo you need to upload it to a hosting site such as Flickr .
Then copy and paste the BB code into your reply .
see my photostream on flickr;
http://www.flickr.com/photos/neilt3/
C & C welcome.
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beeton View Drop Down
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Post Options Post Options   Quote beeton Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2020 at 14:40
I was not able to get to the ear cell. Just no way that I can see to remove that and Sigma service had no schematics. The haze in mine is barely perceptible. Otherwise, lens is very sharp.
 



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Osi View Drop Down
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Post Options Post Options   Quote Osi Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2020 at 15:06
Thank you Neilt. So one has to join another online platform just to post a nondescript picture here. How great
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Osi View Drop Down
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Post Options Post Options   Quote Osi Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2020 at 15:10
Oh, I feel despondent. Please don't make it like a final statement. I've got all these parts lying on the worktable waiting for me to figure out that last piece of the puzzle. I can't accept defeat after all the successes up to this point. Ask elsewhere please. Heeeeelp!
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Post Options Post Options   Quote pegelli Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2020 at 15:33
Originally posted by Osi Osi wrote:

Thank you Neilt. So one has to join another online platform just to post a nondescript picture here. How great
Welcome to Dyxum Osi, I hope you will get your lens fixed.

And unfortunately this "free" site doesn't have the capability to store all the images shown here, cost and server size needed would be prohibitive. So you need one site for your images (there are plenty free ones) and then you'll get us for all the help the membership can provide here
You can see the April Foolishness 2021 exhibition here Another great show of the talent we have on Dyxum
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neilt3 View Drop Down
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Post Options Post Options   Quote neilt3 Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2020 at 20:30
Originally posted by Osi Osi wrote:

Thank you Neilt. So one has to join another online platform just to post a nondescript picture here. How great


It takes a few minutes to sign up to Flickr , and you can store up to a thousand pictures on there .
And it's free .

It also makes things easier when you want help . A pictures worth a thousand words , and it takes guess work out of it .

Regards .
see my photostream on flickr;
http://www.flickr.com/photos/neilt3/
C & C welcome.
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Osi View Drop Down
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Post Options Post Options   Quote Osi Quote  Post ReplyReply Direct Link To This Post Posted: 01 April 2020 at 09:19
I HAVE DONE IT! I came here for help, and now I'm the one who has provided the help! I feel glorious! Ok, I've taken the WHOLE lens apart only to discover I didn't have to. Right at the back of the lens there is an aluminum sealant to the very last lens element and it is the inner part of that group that gets hazy. I severely chipped some metal to succeed in this guesswork (informed as it was nevertheless). Just take the flattest, strongest metal you can find and pry from the inner edge of the outer reaches of the glass and pull the metal up and outward, going around as you do. Alternatively or in addition, stick the narrow strong metal inside the first gap (from middle) an try to pull up also. Don't tell me you won't scratch the metal because it's inevitable -- I don't think they made it to be removed. When you do that, the thin aluminium ring which acts to seal everything up would pop out, followed by an inner separator aluminum, and then the guilty element. THAT'S ALL! Ok, let me go now and see if the haze can be cleaned off. I feel very accomplished. My toughest project has now been carried out. I should add that I feel manual lenses are harder to dismantle than autofocus ones. That's my own experience from doing this thing on over twenty lenses. Cheers
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beeton View Drop Down
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Post Options Post Options   Quote beeton Quote  Post ReplyReply Direct Link To This Post Posted: 01 April 2020 at 13:29
Osi. So, if I understand this procedure, from the rear, after the mount has been removed and the rear plastic ring, the rear cell group is held in by a retainer ring (that's what I call it) and that ring has to be pried out? Can you attach an image of that ring? Many thanks and good luck with the haze.
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neilt3 View Drop Down
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Post Options Post Options   Quote neilt3 Quote  Post ReplyReply Direct Link To This Post Posted: 01 April 2020 at 13:32
It's good your getting it sorted .
A few photos would be extremely helpful as if it's the same lens of mine , I've still to dig them out to clean them up .
see my photostream on flickr;
http://www.flickr.com/photos/neilt3/
C & C welcome.
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Post Options Post Options   Quote neilt3 Quote  Post ReplyReply Direct Link To This Post Posted: 01 April 2020 at 13:35
If you really don't want to set up a free Flickr account , if you taken pictures , send them to me and I'll put them on mine and post them in this thread .
PM me if that suits you better .
It gives people a reference and would be helpful .

Regards , Neil .
see my photostream on flickr;
http://www.flickr.com/photos/neilt3/
C & C welcome.
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