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12-23-2008, 02:22 AM   #1
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Disassembling a lens, advice needed

I recently bought a Vivitar 100mm f2.8 macro, but I realized too late that its aperture blades are oily and close too slowly. I tried accessing the aperture blades from the mount and that was fairly easy to do cause the mount goes off in one piece, no need to take it off part by part, and the last glass element also goes off together with its housing, only three tiny screws holding it in place. But the problem is that it didn't work to clean the blades just form behind. It seems I need front access and I have no clue how to do that. I see only one tiny screw near the top of the lens. I suspect everything starts from this tiny little screw, but I thought it would be much wiser to ask some questions first.

Has anybody tried to disassembly this or a similar lens? Any advice is much appreciated.


PS: I didn't use zippo fluid for the back of the blades, but some kind of gasoline I bought in a pharmacy. Is zippo fluid a better choice?

12-23-2008, 02:28 AM   #2
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Here you can find step-by-step on how to strip down a Super Takumar 50/1.4 lens:
Pentax 50mm f/1.4 strip-down instructions

And here is a link on how to open up an M50/2 lens:
Let

I only opened one Cosina 50mm lens, don't really have any experience w/ bigger lens like a 100/2.8 macro. But I guess the ways they were assembled are pretty similar.

Good luck.
12-23-2008, 02:32 AM   #3
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As long as its not an auto lens it should be ok to dissasemble it, but being that ita a bigger lens it will be harder to put back together.
12-23-2008, 02:46 AM   #4
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Thanks, for the links, I saw both of them before. The problem is that on this lens, there is simply no room to use an eraser and I cannot imagine anything with enough grip to loose the ring around the front lens element.

12-23-2008, 08:13 AM   #5
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Hello and welcome to the forum!

I will just write down what could be useful, hoping that it does apply to your lens (which I do not know).

If you're lazy you could try to slightly bend the aperture lever, so that it does pass the taking mechanism on the cam. If it works, you have a 'manual' lens. You could also just break off that lever from the lens :-)

Tiny screw on front lens barrel: Usually this is a stopping screw for a thread underneath. Loose this screw (check on nearest distance if there are more of these).
Then try to unscrew the whole front barrel with the name ring in one piece. Best done at far distance (lens retracted), cause you will put the torque on the two guiding levers inside.

Name ring: Look for a back lens cap or anything with the fitting diameter. Then, put double side sticky tape on the edge of the cap. Degrease name ring, put cap on the ring with some pressure, unscrew. If loose, continue unscrewing head down. This will minimise the chance for the name ring to tilt off-axis and get stuck.

Hope that some of this is helpful to you,
Georg (the other)
PS: Always always take many photos of each step you're doing. I have just another lens stuck in the queue for not complying to this rule :-(
12-23-2008, 08:21 AM   #6
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QuoteOriginally posted by georgweb Quote
Always always take many photos of each step you're doing. I have just another lens stuck in the queue for not complying to this rule :-(
Good idea! Thank you.
12-23-2008, 09:34 AM   #7
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If the name ring refuses any of the above mentioned methods, you could drill two tiny holes (opposite to each other) into the name ring and insert a simple retaining ring tool to unscrew it.

I once had a name ring, that was glued into place (in addition to the screw thread). In this case it might help to carefully heat the whole ring, until the glue gets soft and the ring can be unscrewed easily.

Anyway, as it looks from your post, disassembling from the front, is what you need, to remove and clean the aperture mechanism.

So, I always planned to do so, I never took photographs of the process. Instead I use a very systematic way to keep all the tiny screws and the parts they hold in the correct order on my work table. For tiny parts I also use specialised little canisters (from Microtools), which prevent the screws from simply vanishing...

Ben
12-23-2008, 12:00 PM   #8
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One more tip - try using a shallow cardboard box or something similar when you're working on your lens.

I lost a ball bearing on my CZJ 50/2.8 because I wasn't following my own advice last week. Good thing it's a cheap lens.

12-23-2008, 01:04 PM   #9
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Another site to try

Best bet will be to head to this web site and ask for info/help

Manual Focus Forum

Lots of very knowledgeable and helpful people there
12-23-2008, 01:08 PM   #10
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These are great advices, thanks guys. I especially like the one with a lens cap and double side sticky tape, that's a really good one. In the meantime, I tried to unscrew the little screw, but it turns out it's stuck. I'll have to find a different screwdriver, I used those small slim ones, they just slip out of my hand.

Reason tells me I should take the lens to a professional, but I am just too curious not to do it myself Curiosity killed the cat, right?
12-23-2008, 02:04 PM   #11
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QuoteOriginally posted by deepbluish Quote
Reason tells me I should take the lens to a professional, but I am just too curious not to do it myself Curiosity killed the cat, right?
Repairing old stuff and especially old lenses is really fun. You will feel really good, if you succeeded. And if not, you will have learned so much, that your next repair-job will go much better!

Ben
12-23-2008, 05:14 PM   #12
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QuoteOriginally posted by Ben_Edict Quote
Repairing old stuff and especially old lenses is really fun. You will feel really good, if you succeeded. And if not, you will have learned so much, that your next repair-job will go much better!

Ben
That's really true

I opened up another lens last night, my second time doing lens surgery:


And the reason why I opened it up? The aperture stayed wide open all the time due to these oily aperture blades (the left two blades were after cleaning):


After about 1 hour, the lens was put together, beautiful as new again:
12-23-2008, 05:42 PM   #13
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Some skillful repairmen flush the aperture blades with Ronsonol (lighter fluid) without completely disassembling the lens.

Chris
12-24-2008, 01:57 AM   #14
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Well, I didn't really have that amount of disassembling in mind, just enough to clean the blades without removing them

I seriously doubt that even if I managed to completely disassemble a lens I would manage to reassemble it so that it actually works
12-24-2008, 05:20 AM   #15
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QuoteOriginally posted by ChrisPlatt Quote
Some skillful repairmen flush the aperture blades with Ronsonol (lighter fluid) without completely disassembling the lens.

Chris
Others do everything with Zippo lighter fluid... I think, this is only a last resort and should mainly used, when things get too complicated. That's why this "method" is en vogue with large format lenses, where you can clean the shutter assembly/apertur with a flush of lighter fluid. And in LF lenses, this whole shutter assembly can be unscrewed from between the lenses easily.

In small 35mm lenses, I wouldn't do it, because if you can get the aperture assembly out of the lens for cleaning, you can do it. If you flush the whole lens assembly with lighter fluid, you will also clean off the lubricants in the focusing threads, which you wouldn't want. And you have to take out any lenses anyway.

Ben
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