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Repairing a Sigma 70-210 f/2.8

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oldglass View Drop Down
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Post Options Post Options   Quote oldglass Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2020 at 16:44
Hi there,

Sorry to bump this thread with a not entirely relevant post (manual focus version of this lens instead of A mount). I posted https://www.dyxum.com/dforum/sigma-70210-f-2-8-minolta-md-disassembly_topic138123.html about my attempts to disassemble and clean this beast of a lens but have not had any luck for nearly 2 weeks so please excuse my cross posting.

Long story short: I've gotten some way into the lens, but have been unable to disassemble the zoom or focusing groups towards the front.

This pic shows how it looks from the back of the lens looking towards the front (if that makes sense). It looks to me like the back of a screw there. There are three sticky-outy tabs with holes like this surrounding the zoom group. Is there any way to remove the front shell (seen at the bottom of the picture with the end of the serial number? That seems to me like the only way to access the front elements. Attacking the lens from the front didn't go well for OP at all so there must be a way in that I've not spotted. Although having said that, it sounds like Osi was going in front-side first but it's hard to say how without pictures.

Thanks in advance
 



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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: 02 April 2020 at 11:36
Thanks for the update .
While things have gone wrong , it's still very helpful to know what's happened ( and how ) so it can be avoided .
Some photos of it in the process of dismantling to gain access to it would still be helpful .
As would your thoughts on if there would have been a better way of doing it .

As I said , I still need to clean mine up !

Cheers .
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 19:11
Pls bear with me. I will be back but I've got to attend to so many stuff ignored the whole day because of this job. Yes, I gained experience for more expensive lenses, but this task is not worth doing, considering the value of the lens (mine I manual only, not converted). I will have to take it apart again and post pics to help out. I just wanted to see it take a photo to know if it's worth continuing on, and it did. Will be back soon. Bear with me. I HATE LENS REPAIRS; I PREFER CAMERA REPAIRS
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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 19:03
Guys, I'm so sorry and extremely FAGGED OUT. I spoke too soon and worse: gave a misleading description. I've just freed myself of this worthless job that has consumed a number of days from me after maybe 10 straight hours (since I posted my last message). I've now destroyed any hopes of re-selling the lens (which is what I do). The damage to metal, and sadly glass, is too much to make it salable. I mistakenly said the lens didn't have to be stripped down; WRONG. I had forgotten that what I was looking at as the rearmost elements of the lens were actually the rearmost elements of the INTERNAL CHASSIS upon which the rest of the lens parts are attached. I didn't realise how deeply I'd gotten into this thing. There's still another group behind this group that actually carries the aperture blades itself. While trying to affix the aluminum ring back, I terribly scratched the glass on that difficult part we're talking about. Reassembling, I see it is very visible up till f4 after which the aperture blades cover it. Most tragically and without reason, I disassembled the frontmost elements that are mated by a helicoild path. I introduced dust, grease and all into it and was not able to put both back when it mattered. After maybe 4 hours and really messing up the whole area, I managed to force them together with a huge amount of particles between and they're jammed in and can't be separated (I used a vice, hammer etc). The guilty glass element seems permanently foggy but I did my best and it is now much better, but not 100% clear. Itself even managed to drop on the concrete floor and I almost fainted; but it didn't break. Quite a thin glass by the way
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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 13:35
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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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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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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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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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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pegelli View Drop Down
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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 2023 exhibition here Another great show of the talent we have on Dyxum
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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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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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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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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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