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Uncleanable lenses
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PostPosted: Mon Aug 06, 2012 4:48 pm    Post subject: repairing lenses... Reply with quote
I have been holding a 400mm vivatar 5.6 prime that needs internal cleaning. I have been looking for a schematic.

what i am really looking for tho on here is a where can I find lens rubber grip. Id love to modify the look of my lenses with older style rubber if I can find it. I hate the waffle rubber of the late 80 and 90s. does anyone know or have experience with it?


PostPosted: Mon Aug 06, 2012 6:01 pm    Post subject: Reply with quote
Carl Zeiss Jena Sonnar 135mm f/3.5. Easy to disassemble but very tricky to put back together. Bought one, fixed stuck blades and wasn't able to put it back on properly again. Please don't do it!

Yashica ML 28mm f/2.8 has unreachable front element, it is cemented and you can only reach it's back slightly from behind after disassembling the front end. Any front element dirtyness won't be easy (if possible at all) to clean.

Jupiter 37AM 135mm f/3.5 also has a cemented block which makes some elements impossible to clean.


PostPosted: Tue Sep 25, 2012 2:05 am    Post subject: Reply with quote
inombrable wrote:
I've cleaned and totally dissasembled three series one 70-210, first one is mine and the other two i sold, everything worked perfect (took me a while but it worked)




Could you answer a question about the tear down and rebuild of the three Vivitar 70-210mm lenses, please:

Were you attentive to collimation issues during the process? Did you see this as an issue?

I have one of those lenses which needs cleaning and rebuilding. I don't even know if collimation is an issue with that lens, it is so old (mine is, anyway) that collimation concerns might not even be appropriate or apply.

But the need to mark each element's rotational position before disassembly . . and then duplicate those same relative rotational positions upon reassembly strikes me as intensely burdensome . . unless it also is mandatory. I work strictly at home and do not have here the equipment to perform lens collimation from scratch. My only way to attend to the matter is to try to duplicate what the factory did when the lens was originally manufactured. I know with certain lenses it's an issue and with others not. But I don't know which are which.


PostPosted: Mon Aug 12, 2013 9:07 am    Post subject: Reply with quote
CZJ Flektogon 4/50 first version zebra - it has front group in metal cartridge with rolled edges. The cartridge can not be disassembled.


PostPosted: Sat Feb 15, 2014 8:22 pm    Post subject: Reply with quote
As suggested by pros (from the local ex-military optics plant), a equal part mixture of tetrohydrofuran, metyletilenketone, cyclohexanone and acetone, when applied in 60C warm bath for 1 hour, will unglue 99% of cemented lens elements.

If you have no idea where to get these cryptic named chemicals, the above mentioned mixture can be bought already as NSF primer for PVC pipes, like this: http://www.amazon.com/Oatey-30750-Listed-Primer-4-Ounce/dp/B000L8DMKQ/ref=sr_1_fkmr0_1?ie=UTF8&qid=1392495109&sr=8-1-fkmr0&keywords=oatley+nsf+primer (Just do not forget to look in MSDS for mentioned chemicals and avoid colored mixtures - might leave tint on lens!)

But use it with extreme caution! this stuff is terribly poisonous when inhaled and easily flammable. So I suggest to use it only outdoors, wearing protective glasses and all necessary stuff.

Regarding the fungus, another suggestion from pros, this time - biologists.

Fungus is the living tissue, so applying vinegar or alcohol does no harm to it at all. While it may wash away fungus from surfaces, it does not kills spores, in fact, fungus can use both vinegar or alcohol as feeding supply (and even above listed poisonous concoction might not be able to break fungus spore cell). Only way to deal with funguss is to break it's cells, most commonly used and easily to get solution is sodium carbonate, available in stores as washing soda. Of course, more exotic alcalis or even gamma rays can be used, but they are less available for home users.


PostPosted: Sat Feb 15, 2014 11:41 pm    Post subject: Reply with quote
hk300 wrote:
Today i talked to a lens repairer and he has heard that some of his old collegues (pity is that he dead several years ago) you could 'cook' the glued lenses in oil (around 200C ) and then the lenses would seperate after some time. Then he used Canadian Tree Balsam to glue the lens element back.

Anyone knows more about this method?


Canada Balsam (CB) is also used as a mounting medium by microscopists to permanently mount specimens.

The solvent for Canada Balsam is Xylene (or Xylol as its sometimes known). The name suggests that it is distilled from wood extract. It's probably better than boiling in oil (type not specified) .I think xylene is not normally used these days as acrylic mounting mediums are 'safer' but I'm sure it can be obtained. New CB will probably come from the same source.

The use of a different 'glue' will alter the refractive properties of the lens. The original lens formula will have been computed to work with CB. The stuff between elements (in old lenses) that yellows or sometimes appears crystalised is almost certainly Canada Balsam.

If you want to unstick CB use xylene. Keep it away from plastic.

I havent unstuck lenses using xylene but i have managed to deconstruct victorian microscope slides sucessfully.


PostPosted: Wed Mar 05, 2014 6:49 pm    Post subject: Reply with quote
Petri 200mm/F4 prime.

The front element consists of two glued elements. Often that glue disintegrates, looking like just someone sweeped with dirty cloth on the lens, so you might think that it is easilly cleanable. It is not, and also, these two elements are mounted press fit in metal ring, almost impossible to disassemble.

Photos coming soon.


PostPosted: Fri Aug 01, 2014 12:06 pm    Post subject: Sigma 400mm 5.6 MF Reply with quote
Prone to haze between the elements of the front group, from browsing around online. This is what the front group from one i got looked like!



I consulted Eddie "the Lens Doctor" Houston by email.

Quote:
I have tried on numerous occasions to re-cement doublet element groups, and never had any success, you will find if you do manage to separate them without any scratching, where the air has entered the cement there will be glass discoloration, and trying to polish this out distorts the glass, even a fraction out and it is no good, so I have given up on trying to repair separation ..........best of luck ..


PostPosted: Tue Dec 16, 2014 4:05 pm    Post subject: Reply with quote
I tried using jewellers rouge and a gem polisher to take off haze see this thread.
http://forum.mflenses.com/hazy-lens-element-not-responding-to-normal-cleaning-methods-t66075.html


PostPosted: Sun Aug 16, 2020 2:40 am    Post subject: Re: Uncleanable lenses Reply with quote
Attila wrote:
I wish to collect here what lenses are not cleanable at home ,because you need to face to face that kind of technical difficulties what is not resolvable at home.

All zooms - they have difficult constructions.Personally I can't open and rebuild when I tried one. Any other opinion?


Agreed. If it's interior elements which need cleaning, I won't even try. Too difficult for me!


Attila wrote:

Vivitar Series 1 28mm f1.9 37xxx it has glued elements you can't open it.


That's interesting, Attila. I had a different experience.
My lens (#3771931) was one of the easier lenses to clean that I've tried. I'm not highly skilled, but I had no trouble removing all the elements in my lens. Although, I believe there is one cemented element pair at the rear.

My own uncleanable lens is a Yashica ML 50mm f/1.9. There's haze in the interior of the front element group. The group is easy to remove from the lens barrel, but the inner element isn't accessible because the lens doesn't have threaded retainers for the front group. The elements are just glued in place.

Having to separate and re-glue elements (even if they're not cemented to each other) is what I consider uncleanable.


PostPosted: Thu Dec 02, 2021 9:28 pm    Post subject: Re: Uncleanable lenses Reply with quote
Attila wrote:
I wish to collect here what lenses are not cleanable at home ,because you need to face to face that kind of technical difficulties what is not resolvable at home.

All zooms - they have difficult constructions.Personally I can't open and rebuild when I tried one. Any other opinion ?


I have taken most Minolta SR mount Rokkor zoom lenses apart (and put back together Wink ). It's not that difficult once you get the hang of it, but then most Rokkor lenses are relatively easy to service compared to some of the other makes.

The only one that got me stuck so far is the Minolta MD III 75-150 f/4, which has the main shroud with DOF scale either glued or press-fitted into the base of the lens, so you can't get to the screws to take the sliding cell mounts out. Tried everything; solvents, heat, unscrewing clockwise, it won't budge. No hidden screw under the plastic red mount indicating dot either. (that's on two of them, so probably a design feature.) Of course can't locate a service manual for that one anywhere...

The floating focus Rokkors (17mm f/4, 20mm f/2.8, 24mm f/2.8, 28mm f/2) need a special tool for re-collimation. The floating rear-cell needs to be temporarily locked into place during collimation, for which a small locking tool was available to service centres. But if you are careful you can get away with measuring the position of the floating cell before disassembly and making sure it ends up in the same place to within 20 microns or so (use a vernier depth-guage).
The Minolta 24mm f/2.8 VFC and Minolta 35mm f/2.8 Shift CA work a bit different, again measure beforehand and re-instate to same position.

The Minolta MC ROKKOR (NL) 21mm f/2.8 has a potentially incurable flaw. Minolta inserted a foam baffle in the gap between the centre cell located in front of the aperture, and the floating front cell holder. I don't know hether this was intended to cut down on internal reflections (unlikely), or act as a dust filter to the significantly "breathing" space between front and rear cells when focussing (more probable). Unfortunately Minolta used the same foam as for their light seals, and we all know what a mess that became after a few decades! The problem is that as this foam disintegrates, at some point it reaches a state where it is both sticky/crumbly, and it starts leaving traces of sticky crumbles on the front element of the center cell. Unfortunately a by-product of this disintegration must be either a strong acid or alkaline, as often this internal element has significant streak-etchings in the glass itself (not just in the coating). Catch it in time and the lens can be saved, otherwise it will remain visible in strong direct light.

The early Minolta MC ROKKOR 16mm f/2.8, underneath the front cell, has an aluminium hold-down ring for the hood that tends to have seized solid in the (also aluminium, doh!) receiving thread. This makes it impossible to remove the selection ring for the colour filters unless you cut the hold-down ring out. Unfortunately that is required for disassembly of the helicoid, which will otherwise also remain inaccessible. On later MC and MD models of that lens Minolta had seen the error of their ways and the hold-down ring was made of brass (easy to remove).

Some early (mid to late 60's era mostly) Minolta lenses used a very soft coating on (usually just a single) internal lens surface. The outer surfaces of the front and rear cells always have hard coatings (outside of front element, rear element, and surfaces facing the aperture blades), so can be cleaned as per usual, but inside the cells take care with any internal coating that has a light green reflection (quite bright reflection, that coating was likely used for Minolta's renowned colour balancing rather than reducing reflections too much). That coating CANNOT be touched, it is very soft. Best you can do is carefully rinse with either acetone, naphta, or isopropyl alcohol if contaminated, and leave to air-dry (thus this may need two of these solvents in succession, where use of one renders the residue soluble in another). Alternatively, if it is scratched beyond use (usually during a previous "service" job), the soft coating means it is easily removed with a mild abrasive, with very little noticeable impact on the lens' performance (gets better, usually) other than perhaps a tiny shift in colour rendering.

Lastly, I would categorise calcium-fluorite APO elements as unserviceable. Too soft, fragile and susceptible to moisture damage.

One obvious tip I have: sometimes it makes sense and is predictable, but at other times for no apparent reasons at all, things screw apart clockwise. Not even the service manuals always mention that... Rolling Eyes


PostPosted: Sat Jan 22, 2022 5:00 am    Post subject: Re: Uncleanable lenses Reply with quote
RokkorDoctor wrote:
Minolta MD III 75-150 f/4


I will cry if I break that one! Laugh 1


PostPosted: Sat Jan 22, 2022 10:45 am    Post subject: Re: Uncleanable lenses Reply with quote
Knudsen wrote:
RokkorDoctor wrote:
Minolta MD III 75-150 f/4


I will cry if I break that one! Laugh 1


Minolta zoom lenses can be a bit difficult. Their zoom cams aren't straightforward screws, but awkward compound ones. The top screws are JIS and easy enough, but the base screws are thick ones with a very fragile slotted head that has a hole drilled in the middle to boot! There is very little "meat" for a flat head screwdriver to grip to turn those screws. Trying to get those base screws out I have had about a 30% failure rate so far. With 6 of those to undo on most zooms, that isn't a great statistic!

I have a scrapper MD zoom I will use to experiment with, see if there is a reliable way of getting those screws out. It appears Minolta used a thread-lock compound on those. Problem is that these screws are not accessible enough to apply acetone near the base to soften the thread-lock, and heating them is also problematic as they are usually right near sensitive cemented doublets & the heavy aluminium parts they are screwed into act as an unhelpful heat-sink...

Given the prevalence of burnished lens mounts inside Minolta MD zoom lenses I suspect that apart from the outer elements, these zooms were never designed to have serviceable innards. Sad


PostPosted: Sat Jan 22, 2022 2:22 pm    Post subject: Re: Uncleanable lenses Reply with quote
RokkorDoctor wrote:
Knudsen wrote:
RokkorDoctor wrote:
Minolta MD III 75-150 f/4


I will cry if I break that one! Laugh 1


Minolta zoom lenses can be a bit difficult. Their zoom cams aren't straightforward screws, but awkward compound ones. The top screws are JIS and easy enough, but the base screws are thick ones with a very fragile slotted head that has a hole drilled in the middle to boot! There is very little "meat" for a flat head screwdriver to grip to turn those screws. Trying to get those base screws out I have had about a 30% failure rate so far. With 6 of those to undo on most zooms, that isn't a great statistic!

I have a scrapper MD zoom I will use to experiment with, see if there is a reliable way of getting those screws out. It appears Minolta used a thread-lock compound on those. Problem is that these screws are not accessible enough to apply acetone near the base to soften the thread-lock, and heating them is also problematic as they are usually right near sensitive cemented doublets & the heavy aluminium parts they are screwed into act as an unhelpful heat-sink...

Given the prevalence of burnished lens mounts inside Minolta MD zoom lenses I suspect that apart from the outer elements, these zooms were never designed to have serviceable innards. Sad


Thank you!

I don't like working on zooms at all, other than minor service, dust etc.

The helicoid seems to work well on my copy. A but nicked up on the finish and a slight dent on the filter threads. I'll probably just go in and clean the glass that I can reach if needed. Right now, it takes very good photos. I have never gone into a helicoid. I've done everything else, but that was 30 years ago. Now I have nerve damage and this work is a lot more difficult. I've only had this lens about a month. So, I will consider this one maybe not uncleanable, but not fully repairable if the helicoid spits hazes or oils stuff. If it fails, I still have a "plain" MD 75-200 in great condition.

That being said, I have some of the beloved MC 58/1.7's and two need service. MC I version has a very stiff helicoid and the MC II version has axial play in the helicoid, and clicks a bit if fast focusing. Third MC II version is in the mail from a very good used dealer that underrates the grade. It was rated "fair" meaning it's probably in "good" condition, maybe between fair and good. The other two were said to be "inoperable" and very inexpensive. I've become very short of time lately and I don't want to leave anything like this unfinished, so the MC I gets delayed, the MC II TBA, after receiving the 2nd copy.


PostPosted: Sat Jan 22, 2022 2:23 pm    Post subject: Re: Uncleanable lenses Reply with quote
RokkorDoctor wrote:
Knudsen wrote:
RokkorDoctor wrote:
Minolta MD III 75-150 f/4


I will cry if I break that one! Laugh 1


Minolta zoom lenses can be a bit difficult. Their zoom cams aren't straightforward screws, but awkward compound ones. The top screws are JIS and easy enough, but the base screws are thick ones with a very fragile slotted head that has a hole drilled in the middle to boot! There is very little "meat" for a flat head screwdriver to grip to turn those screws. Trying to get those base screws out I have had about a 30% failure rate so far. With 6 of those to undo on most zooms, that isn't a great statistic!

I have a scrapper MD zoom I will use to experiment with, see if there is a reliable way of getting those screws out. It appears Minolta used a thread-lock compound on those. Problem is that these screws are not accessible enough to apply acetone near the base to soften the thread-lock, and heating them is also problematic as they are usually right near sensitive cemented doublets & the heavy aluminium parts they are screwed into act as an unhelpful heat-sink...

Given the prevalence of burnished lens mounts inside Minolta MD zoom lenses I suspect that apart from the outer elements, these zooms were never designed to have serviceable innards. Sad


Thank you!

I don't like working on zooms at all, other than minor service, dust etc.

The helicoid seems to work well on my copy. A but nicked up on the finish and a slight dent on the filter threads. I'll probably just go in and clean the glass that I can reach if needed. Right now, it takes very good photos. I have never gone into a helicoid. I've done everything else, but that was 30 years ago. Now I have nerve damage and this work is a lot more difficult. I've only had this lens about a month. So, I will consider this one maybe not uncleanable, but not fully repairable if the helicoid spits hazes or oils stuff. If it fails, I still have a "plain" MD 75-200 in great condition.

That being said, I have some of the beloved MC 58/1.4's and two need service. MC I version has a very stiff helicoid and the MC II version has axial play in the helicoid, and clicks a bit if fast focusing. Third MC II version is in the mail from a very good used dealer that underrates the grade. It was rated "fair" meaning it's probably in "good" condition, maybe between fair and good. The other two were said to be "inoperable" and very inexpensive. I've become very short of time lately and I don't want to leave anything like this unfinished, so the MC I gets delayed, the MC II TBA, after receiving the 2nd copy.
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