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09-17-2008, 12:12 AM   #1
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How to fix sticky/slow blades?

Hello,

I just got an older 35mm with a blade problem.
It feels like there is resistance to blade movement, both opening and closing.

Any suggestions on how to deal with this or where to look?
I've tried searching for this, but couldn't find anything useful.

Help/comments would be greatly appreciated.

Cheers,
Tim.

09-17-2008, 12:19 AM   #2
Damn Brit
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Have you tried gentle warming? Leave it on the back of your tv or computer for a while.
Maybe even in your pocket. It might help.
09-17-2008, 12:38 AM   #3
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QuoteOriginally posted by Damn Brit Quote
Have you tried gentle warming? Leave it on the back of your tv or computer for a while.
Maybe even in your pocket. It might help.
Gentle warming, eh?
Never heard of that one before. I'll give it a try.

Although, I have tried fixing it the same way I "fix" everything else - just hit it on the side a few times. No luck... go figure.
09-17-2008, 12:47 AM   #4
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QuoteOriginally posted by TimB Quote
Gentle warming, eh?
Never heard of that one before. I'll give it a try.

Although, I have tried fixing it the same way I "fix" everything else - just hit it on the side a few times. No luck... go figure.
If it hasn't been used for a while it hopefully just needs time to ease up.
Someone mentioned in a thread I read yesterday, I think it was a Russian lens, that he warms it in his hands when it's cold before he uses it.

09-17-2008, 01:03 AM   #5
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Well.. what you need to do, is get a big mallet...
09-17-2008, 02:10 AM   #6
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Sticky blades - sometimes - perhaps most times, caused by oil migrating from the lens focussing helicoid grease onto the aperture - open up the lens and clean the blades with solvent and close up again. Could need two or three goes to get it all out. That is the summary - the full story plus alternate links is here:
Sticky Aperture
09-17-2008, 04:11 AM   #7
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A rant

QuoteOriginally posted by TimB Quote
Help/comments would be greatly appreciated.
RANT
Please, please, please do NOT help by giving full information about your lens. It's a lot more fun to guess, provide useless information, and waste everyone's time.
Rant complete.

Having said that, Eric Hendrickson ALSO repairs Pentax lenses of a certain vintage. So, if the lens in question is an M42, or one of the early K mounts, you might check with him. He recently disassembled and cleaned a Super Tak 35/2.0 for me. Besides fixing the sticky blades he will probably remove any dust that has crept inside the lens, remove fungus if present, and return a lens to you which will be as close to new as it is possible to have.

I suggested Eric, because I am in no way qualified to dissemble, clean and reassemble a lens. Try not to lose any of the parts though. Eric will want them if you send the lens to him.

Last edited by wlank; 09-17-2008 at 04:15 AM. Reason: correction
09-17-2008, 10:57 AM   #8
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QuoteOriginally posted by Arjay Bee Quote
Sticky blades - sometimes - perhaps most times, caused by oil migrating from the lens focussing helicoid grease onto the aperture - open up the lens and clean the blades with solvent and close up again. Could need two or three goes to get it all out. That is the summary - the full story plus alternate links is here:
Sticky Aperture
Thanks for the info and the link. I figured it had something to do with lubrication, just wanted to see if others had experiences to share on this matter.

Any idea on the kind of "solvent" everybody keeps mentioning?
I figured methanol or isopropanol would do the trick.
If that fails, maybe acetone is worth a shot. Although, I'm a little hesitant about that, because I can't have it touch any seals.

09-17-2008, 11:06 AM   #9
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QuoteOriginally posted by wlank Quote
RANT
Please, please, please do NOT help by giving full information about your lens. It's a lot more fun to guess, provide useless information, and waste everyone's time.
Rant complete.

Having said that, Eric Hendrickson ALSO repairs Pentax lenses of a certain vintage. So, if the lens in question is an M42, or one of the early K mounts, you might check with him. He recently disassembled and cleaned a Super Tak 35/2.0 for me. Besides fixing the sticky blades he will probably remove any dust that has crept inside the lens, remove fungus if present, and return a lens to you which will be as close to new as it is possible to have.

I suggested Eric, because I am in no way qualified to dissemble, clean and reassemble a lens. Try not to lose any of the parts though. Eric will want them if you send the lens to him.
COUNTER-RANT
Simmer down now. I didn't realize there are significant differences in aperture assemblies between various mounts.
Besides, there has been useful info provided so far, especially the mallet technique.

Having said that, my lens is an M35/2.8.
I appreciate the repair service referral, but it'll probably be too expensive to send the lens out.
Plus, I was looking forward to a DIY opportunity here.
09-17-2008, 11:12 AM   #10
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If you can't put it back together again, you have a nice paperweight.
09-17-2008, 11:23 AM   #11
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QuoteOriginally posted by Damn Brit Quote
If you can't put it back together again, you have a nice paperweight.
Heh, glad to see that I can always count on friendly encouragement from fellow forum members
09-17-2008, 12:30 PM   #12
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QuoteOriginally posted by TimB Quote
COUNTER-RANT
Simmer down now. I didn't realize there are significant differences in aperture assemblies between various mounts.
Besides, there has been useful info provided so far, especially the mallet technique.

Having said that, my lens is an M35/2.8.
I appreciate the repair service referral, but it'll probably be too expensive to send the lens out.
Plus, I was looking forward to a DIY opportunity here.
Well, I doubt Eric will work on CJZ or other M42 or K mount lenses, but he might. And you might be surprised how inexpensive he is. I do agree that if you ar going to use the mallet technique, it is universal, and no one needs to know what lens. I'm sure it will work on all of them.

If you do go the DIY route, take some pictures for us.


QuoteOriginally posted by Damn Brit Quote
If you can't put it back together again, you have a nice paperweight.
Just don't loose the parts, and Eric will fix and reassemble it. I have experience in this area.
09-17-2008, 01:17 PM   #13
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QuoteOriginally posted by TimB Quote
COUNTER-RANT
Simmer down now. I didn't realize there are significant differences in aperture assemblies between various mounts.
Besides, there has been useful info provided so far, especially the mallet technique.

Having said that, my lens is an M35/2.8.
I appreciate the repair service referral, but it'll probably be too expensive to send the lens out.
Plus, I was looking forward to a DIY opportunity here.
Tim, I don't have the 35/2.8 but several (over the years) 35/2 Ms. These are infamous for the sticky aperture blade syndrome. Pentax obviously used a grease which after a couple of years migrated into the aperture mechanism.

In my experience this needs a major operation, as it usually does not work, to just clean the visible part of the aperture blades - which could be done easily enough by unscrewing the rear lens element. You really need to get onto the aperture group itself, which is done via the front of the lens:
- remove name ring, by screwing it out through the filter thread
- remove front barrell assembly (usually fixed by three or four screws
- remove (probably, but here the case with your lens may be different from the lenses I cleaned) front tube from focus thread (you will have fun reasembling this!)
- if you are lucky, you can now reach the aperture assembly, by unscrewing several tiny screws. Alternatively you have to remove those screws from the back of the lens, in which case you first remove the K-mount, then the rear lens element (beware of losing the tiny ball, which provides the click stops of the aperture ring)

When you take out the aperture assembly be careful. Sometimes their housing is screwed together, sometimes it is loose and falls apart, as soon as you try to get it out of the lens. But as you have to take it apart anyway... You need to clean out the interrior of the aperture assembly housing and the blades itself with Isopropanol. Don't use acetone. it is very effective, but sometimes aperture blades and housing parts are made of plastics, which will be damaged by the acetone.

Do not applay any oil or grease at all to the aperture mechanism. It is not necessary and the mechanism will work fine without any lubrication.
Have fun and keep track of all the tiny screws, as these are hard to buy as replacements.

Some remarks: Pentax on many lenses used Locktight for securing the screws. The Locktight they used is often more of the Superglue variety and it might be very difficult to remove the screw, without shearing off the screw head. In very stubborn cases I used a gas soldering iron to heat the glue, until it was soft enough to turn the screws. In one extreme case I had to heat a thread around the complete lens barrell in that way, which is nerve wrecking, if the lens is an expensive one...

Ben
09-17-2008, 03:00 PM   #14
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Ben,

Thanks a lot for the info. This is pretty much what I was looking for.
I don't know how similar the 35/2 is to the 35/2.8, so I don't know how applicable your schematic descriptions will be, but I'll surely find out when I get home tonight
09-17-2008, 03:02 PM   #15
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QuoteOriginally posted by wlank Quote
Well, I doubt Eric will work on CJZ or other M42 or K mount lenses, but he might. And you might be surprised how inexpensive he is. I do agree that if you ar going to use the mallet technique, it is universal, and no one needs to know what lens. I'm sure it will work on all of them.

If you do go the DIY route, take some pictures for us.
I'll make sure to document stuff as I go along.

Taking bets on how many "extra parts" I'll have after this is done
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