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Tamron 90/2.5 52B Reassembly?
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PostPosted: Thu May 29, 2014 3:31 am    Post subject: Tamron 90/2.5 52B Reassembly? Reply with quote
I was experiencing problems with the aperture on my 52B, the same problems as described in this thread. Specifically the aperture was snapping open when focusing, and also failing to open or close beyond a certain point. So I figured I would dive in and see what was up.

That was a terrible, terrible idea.

I have the lens fully disassembled, save for the optical block. I cannot figure out how to get those opposing helicoids back together correctly. I've had them threaded back together several times now, but the positioning is always off. Is there a trick to this?


PostPosted: Thu May 29, 2014 7:17 am    Post subject: Reply with quote
The trick would have been to mark the correct position before you disengaged the helicoids. Now your only option is to try every possible combo. It's a PITA, but it can be done.


PostPosted: Thu May 29, 2014 12:09 pm    Post subject: Reply with quote
Gardener wrote:
The trick would have been to mark the correct position before you disengaged the helicoids. Now your only option is to try every possible combo. It's a PITA, but it can be done.


Agreed. The only "trick" now remaining is:

If at first you don't succeed, try, try again.

Those tries could consume a remarkable amount of time, though. Wink


PostPosted: Thu May 29, 2014 8:55 pm    Post subject: Reply with quote
What a blunder. I'll come back and attack it again one day.


PostPosted: Thu May 29, 2014 9:17 pm    Post subject: Reply with quote
It's worth saving, I spent hours trying the different permutations of which element went where, and which way up, after I took it apart to clean slight fungus from one element, laid them all out carefully the right way and in order, then kicked the table leg and sent them flying! Rolling Eyes I took it out today, it's one of my favorite lenses.

Persevere. Wink


PostPosted: Thu Jul 31, 2014 11:45 pm    Post subject: Reply with quote
Any chance of a brief disassembly outline/info? I have a 52B with a sticky/crunchy focus.


PostPosted: Sun Aug 03, 2014 12:19 am    Post subject: Reply with quote
Any information I had is lost, my old computer crashed and it's gone. But there is some information on the internet, I'll have a look.


PostPosted: Fri Aug 08, 2014 2:27 am    Post subject: Reply with quote
http://www.wiratama.net/camera/category/adaptall2a93b47ccbf

http://k10dpentax.blogspot.sg/2011/04/cleaning-haze-tamron-sp90-f25-52b.html


PostPosted: Fri Aug 08, 2014 1:32 pm    Post subject: Reply with quote
Excellent links, really good information there.


PostPosted: Fri Aug 08, 2014 4:32 pm    Post subject: Reply with quote
Good info (tho the one is actually for the 52BB) have to have a go at my 52B,..


PostPosted: Sat Aug 09, 2014 3:57 am    Post subject: Reply with quote
I believe the only differences are cosmetics.

marcusBMG wrote:
Good info (tho the one is actually for the 52BB) have to have a go at my 52B,..


PostPosted: Sat May 23, 2020 4:30 pm    Post subject: Reply with quote
I am seeking some help about this lens but more generally about cementation issues.

I recently bought an excellent Tamron 52B and realised after a while a VERY slight haze behind the front group. When observed in the sun there is no problems but under a led light and at approx 45° angle the veil is there.

I do not suffer from loss of contrast in normal conditions but if sun is close or in the viewfinder there is an issue.

I followed the excellent explanations given under the link found above https://k10dpentax.blogspot.com/2011/04/cleaning-haze-tamron-sp90-f25-52b.html

opened the lens and realised it was not haze but a kind of veil in a cemented group (the one in second position). After cleaning the surfaces of the cemented group the veil was still there and obviously at the junction level.

I managed to put the lens back together (happy I managed to do it).

I know I should live with it and take nice photos rather than try to solve a non problem but my nature is otherwise.

So my question is: Is there a way to cure cementation problems other than fully decementing and recementing which might be above my skill levels. I don't have V blocks (and one of the lens forming the group is somewhat tapered) and obviously do not own a collimation laser.

I do not know if the group is cemented with Canada balm or something epoxy.

My secret wish is that someone having experienced this issue has put the group in an oven at a temperature allowing cementation to get back to its original state without complete decementation and movement between the cemented elements.

I might be asking too much. Thanks for any insights.


PostPosted: Sat May 23, 2020 5:54 pm    Post subject: Reply with quote
lumens pixel wrote:

opened the lens and realised it was not haze but a kind of veil in a cemented group (the one in second position). After cleaning the surfaces of the cemented group the veil was still there and obviously at the junction level.

I managed to put the lens back together (happy I managed to do it).

I know I should live with it and take nice photos rather than try to solve a non problem but my nature is otherwise.

I know, it is not the answer you are looking for, but it is still an answer nevertheless:





One of these Zuikos 50/1.4 has pretty significantly clouded doublet.
If not for the wide open torch sensor blasting controlled comparison, I wouldn't be able to tell.

I thought clear Zuiko will be more flare-resistant in real world shooting, but in practical application it is not.
Turns out flare resistance in general wasn't really a fault due to haze, it's just how it is with this optics.

In the end, I did put together a clean copy around better doublet, but if i knew beforehand, I would not bother.


PostPosted: Sun May 24, 2020 9:23 am    Post subject: Reply with quote
Thanks Aidaho. This is good for the morale. Obviously I am also seeking relief for not having been able to spot the problem at time of purchase. But you are right I would have hoped to hear about a solution that would permit to restore the group to its original state. I suppose it's possible if it's Canada balsam but you can probably not cook again epoxy.


PostPosted: Sat Aug 12, 2023 12:18 pm    Post subject: Reply with quote
lumens pixel wrote:

...
I recently bought an excellent Tamron 52B and realised after a while a VERY slight haze behind the front group.
...
opened the lens and realised it was not haze but a kind of veil in a cemented group (the one in second position). After cleaning the surfaces of the cemented group the veil was still there and obviously at the junction level.


I had the same problem (slight haze behind the front group) - BUT after taking the lens apart it turned out that the haze was on the last (innermost) surface of the doublet (second element / third lens from the front). Cleaning the surface with two or three drops of a common dishwashing detergent the doublet was clear again. It seems a bit strange that a cemented surface would develop haze, given th fact that the cement (be it canada balm or an epoxy) would have to separate from the glass surface. That in itself would probably lead to much stronger veiling effects than "VERY slight haze". I suspect the haze on your lens simply was a bit reluctant to come off ...

S

PS re-inserting said doublet into its retainer was abit tricky since the tolerances between retainer and glass element obviously are pretty tight.


PostPosted: Sat Aug 12, 2023 1:54 pm    Post subject: Reply with quote
stevemark wrote:
lumens pixel wrote:

...
I recently bought an excellent Tamron 52B and realised after a while a VERY slight haze behind the front group.
...
opened the lens and realised it was not haze but a kind of veil in a cemented group (the one in second position). After cleaning the surfaces of the cemented group the veil was still there and obviously at the junction level.


I had the same problem (slight haze behind the front group) - BUT after taking the lens apart it turned out that the haze was on the last (innermost) surface of the doublet (second element / third lens from the front). Cleaning the surface with two or three drops of a common dishwashing detergent the doublet was clear again. It seems a bit strange that a cemented surface would develop haze, given th fact that the cement (be it canada balm or an epoxy) would have to separate from the glass surface. That in itself would probably lead to much stronger veiling effects than "VERY slight haze". I suspect the haze on your lens simply was a bit reluctant to come off ...

S

PS re-inserting said doublet into its retainer was abit tricky since the tolerances between retainer and glass element obviously are pretty tight.


Haze between two cemented elements does occur unfortunately.

I have a cemented doublet removed from a Bronica PS lens, which has haze between the two cemented elements. Impossible to tell whether one of the cemented glass surfaces has developed haze or whether it is the cement layer itself.

I am hoping the cement is the problem, then after separation & cleaning, re-cementing would be an option at least.

Failing the legal means of access to methylene-chloride here I have tried to soak the doublet in acetone for several months; no luck, the cemented elements won't separate.

Last option is to try Norland's recommended alternative separation method for UV-cured epoxy; a 45 minute bath in 200˚C / 400˚F mineral oil, but I have yet lacked the courage to try that (although I have nothing to lose; the lens is unusable in its current hazed state).
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