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Dennisdietz
Tinkerer
Username: Dennisdietz
Post Number: 16
Registered: 08-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 29, 2008 - 07:18 pm: | 
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Hey all,
I just got this lens and the aperture mechanism seems to be disconnected. Neither the ring or camera lever will make any change on the aperture, it seems to be constant 2.8 It does not look to have been disassembled. I tried to remove the mount to access the aperture mechanism, as typical for Nikons', but the mount seems to be held in from the inside. It will turn a little and seems loose, but acts like there is some clip holding it from the inside.
Some reading on the net indicates that the aperture mechanism must be done from the front. Is this correct? If so, or if not, does anyone have any experience disassembling this lens.
I got it really cheap and it is otherwise pristine so returning it seems to be folly. It really does not seem broken and I am guessing someone tried to go in from the back before me and now something is off. |
Harryrag
Tinkerer
Username: Harryrag
Post Number: 29
Registered: 05-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, December 31, 2008 - 03:03 am: |
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With all the zooms I know you go in from the front, removing the mount may leave you with a set of new problems, especially if springs become unhooked in the process of a step by step teardown.
I have not worked on a Vivitar 28-90, though. |
Dennisdietz
Tinkerer
Username: Dennisdietz
Post Number: 18
Registered: 08-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, December 31, 2008 - 10:30 am: |
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Thanks Harry.
A little update... I was able to get the mount off, thanks to a friend's tips on the No-metering Flickr group. You have to remove the baffle around the inside of the mount then you can see where the aperture cam linkage can catch. In my case, the camera to aperture lever spring had come off and was catching, preventing me from getting the mount all the way off. Removing the baffle allowed access to that. It took me a while to figure out how it all went back together but I eventually got it. The hardest part is loading the spring for the aperture arm, which is loaded against the body of the lens. This was doable by assembling the mount/linkage with the spring turned 180 degrees around its pivot. Then, using tweezers and a pencil eraser, I was able to bend the spring around put the end behind the post that holds it. Now the aperture mechanism works well.
The second problem is that the blades have oil that prevents them from working properly. This is apparently fixed though the front of the lens by removing the front and inner element. I am able to remove the front element but can't seem to get the inner one to budge, even using the spanner holes. I've emailed a friend who has done this before to see if he has any tips and to make sure I am on the right path. I'll update once I figure everything out.
Best all,
Dennis |
Dennisdietz
Tinkerer
Username: Dennisdietz
Post Number: 19
Registered: 08-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, December 31, 2008 - 02:04 pm: |
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Success! Here is what I did...
Removed the front element by unscrewing the name ring. This is a normal lefty-loosey thread.
Remove the inner element. There are two spanner holes but the element was so tight I could not use them. I ended up using padded pliers on the element ring. This required a lot more force that I was comfortable with but steady pressure broke it loose. From there I used a pointed awl to spin the element out. This exposes the aperture blades. They were really oily.
I tried cleaning with gentle pressure and a q-tip bit it was to much of a pain so I scratched index marks on the aperture blade assembly and removed the screws visible. This frees the aperture assembly and it can be lifted straight out. To aid pulling it out and later putting it back in, I used two chopsticks with a film case between them and rubber bands on each end to hold it all together. This makes a giant set of expanding grippers that can grab the inside of the outer ridge of the aperture assembly.
I then diligently cleaned the blades using qtips, a bulb blower and a little lighter fluid. I wanted to use acetone but I'm snowed in today. I used just enough lighter fluid to loosen and sticky old oil then wiped (in the direction of the blades), blew into the center to force oil out, open close the blades, wipe with qtip.... etc. I did this for about an hour till they seemed really dry and moved freely. Time will tellif I have removed enough oil.
Reassemble in reverse order, making sure to get the aperture blade pin into the fork that goes to the ring/camera lever mechanism. Insert the screws and lightly tighten then adjust so that f/2.8 is the max blade opening and tighten the screws. I had indexed the position before removal but these index marks did not line up upon re-assembly. I believe though that my final technique to align the blades is correct.
Clean, blow-out and reassemble the rest of the elements. Go take some sexy photos.
One note on assembling the mount/aperture assembly. The end silver pin on the aperture cam follower goes into the slot on the raised portion of the aperture blade connection mechanism. That may not make much sense now but it will when you have the thing apart.
Best of luck to all!
Dennis Dietz |
Harryrag
Tinkerer
Username: Harryrag
Post Number: 30
Registered: 05-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 02, 2009 - 04:30 am: |
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Aperture linkage can easily and accidentally be bent inside zooms, so there is no need to worry about previously made index marks not exactly lining up on reassembly, if you otherwise compensate that alteration of parts. I guess that manufacturers made it that way so everything could be lined-up quickly.
What I do usually do is similar to the process you describe.
In some Cosina/Vivitar/Exakta/... branded zooms the aperture module can often be used for different camera mounts, this is to say a 180 deg shift of the operating lever inside offers the choice to get maximum opening either to the right or to the left. I did not notice that at first, so after reassembly only the pics in mid-range (about f 5.6) were exposed correctly, the others showed under or overexposure, resp. The aperture rings of otherwise identical lenses for different camera makes can also be swapped, but if you make one operational zoom lens from parts of several junkers it may happen you mix them up and end with a lens showing wrong figures on the index ring!
One more word about removal of oil from the blades. I usually do everything at least twice to make sure all oil is gone, then wait for a few days before reassembling the mechanism. Often oily residue creeps back all over the blade, again causing stickiness, if this occurs after a month or so you have to start all over again.
I have learnt the hard way to be extremely cautious about the use of acetone, so I consider this a last straw measure. Sometimes aperture blades, in some cases also those in shutters, have a kind of low-friction coating which is very vulnerable to acetone. |
Dennisdietz
Tinkerer
Username: Dennisdietz
Post Number: 20
Registered: 08-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 02, 2009 - 06:03 am: |
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Thanks Harry for the insight there, especially about the dangers of acetone. IS there anything you would use to clean the blades? In my case here, the biggest cleaning problem came from the back side of the blades that was inaccessable due to there being a thin lens directly behind and part of the aperture blade assembly. That assembly had three screws on the side and seemed to come apart but I was hesitant to try since I do not know how the blades are assembled. I did not want to open the hing and have blades fall out...
Best,
Dennis |
Harryrag
Tinkerer
Username: Harryrag
Post Number: 31
Registered: 05-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 02, 2009 - 01:50 pm: |
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Whenever lighter fluid turns out to be unsuitable I prefer isopropyl (alcohol) as a cleaning agent or solvent for critical applications.
I thought you had extracted the aperture module from the lens. Maybe ceretain zooms are somewhat similar in design, I found a lens element like the one you speak of directly screwed into a thread in the aperture assembly of a Cosina 28-200 and also at the same place in a no-name 35-135 (Tamron design?) from where they could be removed once the whole thing was outside the lens barrel. Cleaning the blades in a bath is then usually no problem. |
Dennisdietz
Tinkerer
Username: Dennisdietz
Post Number: 21
Registered: 08-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 02, 2009 - 06:21 pm: |
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Harry, I tried a little isopropyl but it seemed to bead up so much that I though it may be ineffective. My dangerously limited knowledge of chemistry tells me that a polar, hydrogen-bound, short-chain alcohol will make a poor solvent for a non-polar, hydrocarbon used for lubrication. However, I it would have been more effective than I suspect and since it would not have any chance of hurting the glass element that is part of the diaphram assembly, I likely could have soaked the whole thing. Additionally, the alcohol would pull out any trapped moisture....
Anyway, here is a link to my flickr with a photo of the aperture assembly removed. Its hard to see in the phot but the lens is about 1/16" (~1.5mm) behind the blades.
<a href="http://www.flickr.com/photos/dennisdietz/3156673126/"><img></a> |
Dennisdietz
Tinkerer
Username: Dennisdietz
Post Number: 22
Registered: 08-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 02, 2009 - 07:04 pm: |
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Well, its already stuck so I guess tomorrow I'll try the alcohol. |
Mndean
Tinkerer
Username: Mndean
Post Number: 118
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 02, 2009 - 08:18 pm: |
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Harry and Dennis,
I used to use isopropyl alcohol for dirty/oily aperture elements. It only worked well when I used anhydrous (hard to find), and the dirt and oil were light. Most of my lenses that needed cleaning were like that at the time, so it was fine. When I found a heavier layer of oil on the blades, it didn't work as well as lighter fluid. I can find lighter fluid cheap enough to make it a no-brainer to use now. |
Dennisdietz
Tinkerer
Username: Dennisdietz
Post Number: 23
Registered: 08-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 02, 2009 - 09:09 pm: |
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Yeah, I just tried isopropyl and it seems to have worked well. Turns out oil and alcohol don't mix, but if there is only alight bit of oil, as Mndean says, the alcohol will wash some of the oil up and cause beading. You actually get these little balls of water(70% alcohol) and oil that are easily wiped up.
The technique I used here was to qtip a "lot" of alcohol, enough to flood the surface but not to run off into the rest of the mechanism or onto the lens. I did this and qtiped off the excess, and repeated several times. This visibly removed almost all the oil, much more than yesterdays attempt. Next, I cut a 4 layer of lens tissue into a circle about the size of the open aperture. I carefully tucked this behind the blades as I closed them (a toothpick works good for this)... CAREFULLY!. Then I wet the tissue a little and wet the surface of the blades a little. Then, while still wet I opened the blades while lightly pressing down on the blades with a qtip. This seemed to work very well in wiping the excess oil/alcohol off the back of the blades that other attempts failed at.
I'll wait till tomorrow to double check this time before reassembly.
Another tip, if the face ring folding the first element is hard to get off, make sure you loosen the three set screws holding it. These are located on the outside of the largest part of the lens barrel.
Best,
Dennis |
Mndean
Tinkerer
Username: Mndean
Post Number: 119
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, January 03, 2009 - 06:08 am: |
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Dennis,
That's why I used anhydrous isopropyl instead of 70%, it didn't bead and it dried very quickly. I had a place to easily get it back then, though. |
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