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Repairing a Sigma 70-210 f/2.8

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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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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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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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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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Osi View Drop Down
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Post Options Post Options   Quote Osi Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2020 at 18:24
Hi everyone. I did send the only picture I took of the completely disassembled lens to someone on here by e-mail but he said he was no longer going to attempt any further to work on it since his wasn't that bad. For the last poster's situation: indeed the focusing lens group is in the very front part. To access it, you will observe that the entire front section has a wider diameter than the focusing grip part. Take your hands from the very front of the lens all the way to the end of that part with same diameter. At the end of it, before the focusing grip is a ring deceptively placed there to lock the front barrel in place. Looking from the back of the lens, turn the ring in the normal anticlockwise direction and voila, the front barrel comes off going further forward. The very first front glass is attached to the rest of the lens by just a black tape! I'm sure you can figure out the rest or else my response will get too long and unwieldy. Please let me know how it went
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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 19:52
Wow, thanks for the quick reply, Osi!

Just to confirm, the ring I should be twisting is the ring pictured here around which I've placed the rubber band? I've tried twisting it a few times and just want to be sure before I tire myself out too much!
 



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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: 29 May 2020 at 20:13
Yes, that's the one. It is difficult at first as when you tighten you grip, you may be squeezing it out of round. Try from a few angles. Normal direction (left).

When you get it off, the front barrel will come off (with the af version). The front element AND barrel underneath are held in place with tape. Do NOT take that tape off without first marking the front to rear sections or you will have difficulty aligning them back on.

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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: 29 May 2020 at 20:21
Originally posted by oldglass oldglass wrote:

Wow, thanks for the quick reply, Osi!

Just to confirm, the ring I should be twisting is the ring pictured here around which I've placed the rubber band? I've tried twisting it a few times and just want to be sure before I tire myself out too much!

Thankfully, someone else has chimed in to validate. I was still waiting for your link to produce a picture to no avail. The picture policy of this forum is an Achilles heel
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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 20:30
Originally posted by Osi Osi wrote:

I was still waiting for your link to produce a picture to no avail. The picture policy of this forum is an Achilles heel


I uploaded my images to an external hosting service (Imgur). Perhaps the forum software mangled the link for you? Try going to i.imgur(dot)com/waX8gFs.jpg
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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: 30 May 2020 at 13:53
Originally posted by Osi Osi wrote:

The picture policy of this forum is an Achilles heel

Judging by the amount of pictures posted on this forum on a daily basis it can't be that hard: see here for instructions

Btw, good luck with the lens repairs
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: 30 May 2020 at 14:09
Originally posted by pegelli pegelli wrote:

Originally posted by Osi Osi wrote:

The picture policy of this forum is an Achilles heel

Judging by the amount of pictures posted on this forum on a daily basis it can't be that hard: see here for instructions

Btw, good luck with the lens repairs


As explained in March , it's simple and free to start a Flickr account to post images on here , and other places .

I also offered to put the images on my Flickr site and post them in this thread to help others in the future .
Not been taken up on the offer though . Shame .
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: 30 May 2020 at 15:52
Hi. I did take somebody up on the offer and sent a picture to their e-mail as I recently mentioned. Probably wasn't you then. Please send me your e-mail as a direct message so I can do same. I recently lost a phone containing over 500 pictures of different cameras and lenses under varying stages of disassembly which I use myself. I can regard myself as fairly experienced now and I've always been a competent person (but camera/lens repairs seriously challenged that and I incurred many knocks in the learning process) and I benefitted immensely from online fora like this (still do, hence my appearance here) and I find it fulfilling if I can help others also. I'm just not in sync with the picture policy here. I want to be able to type stuff and click on an attachment tab and upload a picture from my phone. This is what I'm used to. Maybe that would change but for now, I'd rather do it the way I've proposed. We're all in it together (Lol)
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Post Options Post Options   Quote neilt3 Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2020 at 16:25
Hi Osi .
That's a sickner losing your phone with all the images on , I know how valuable they are for reference .

I've P.Med you my email address .

When I get chance I'll get them on Flickr and posted here so anyone doing a search can find them .
Hopefully they will be of help to others .
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: 30 May 2020 at 17:15
Hi. I have sent a message to the e-mail address you provided, with pictures. They were supposed to be for me only. If I knew I would be sharing them with the world, I'd have done a better job of it. Fun fact: I'm in Nigeria!
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