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Old Sep 2, 2008, 2:34 AM   #1
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Hi all. Raised in a darkroom outside Los Angeles, I photographed with film and chemicals for a long time, for better or worse. I've been exclusively electronic and digital for about 15 years now, moving images into computers to be manipulated and torn apart with PaintShopPro.

I bought a Pentax K20D dSLR a very few months ago, causing me to neglect my Sony, Olympus and Minolta PNS cams. LBA (Lens Buying Addiction) is destroying my budget on eBay, but I have a lot of nice German, Russian and Japanese lenses now. I'll have to stop sometime soon, won't I?

Other than going broke, my problems are slightly esoteric. I have a Vivitar 24/2 on a Pentax-K mount, and the aperture ring turns loosely. The iris blades don't move. Can anyone suggest how to perform surgery on this lens?

I use many M42 and M39 screwmount lenses on the Pentax, via adapters. I've seen some Russian 16mm cine cams offered on eBay, with tempting zoom lenses with M42 or M39 mounts. The APS-C sensor on the Pentax is nearly the same size as a 16mm frame, or a 35mm half-frame. Does anyone know if these Russian lenses, with names like Meteor, could be used on my dSLR? This is a matter of matching the register or working distance, which is around 45.5mm.

I have other lens problems, but I'll bring them up in other forums here. Hope I don't wear out my welcome, eh?

--RioRico
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Old Sep 2, 2008, 6:14 AM   #2
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Welcome.

We have some Pentax members that I've seen demonstrating modifications to lenses, and it's not uncommon to see them experimenting with different lens mounts.

With a little luck, one of them may be able to give you some answers.

So, I'll move post down to our Pentax Lenses Forum, where they may see it and chime in.

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Old Sep 2, 2008, 8:03 AM   #3
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Hi! I'm not the one who can really help you - there are several people around here who are better at lens repair. The only trouble I've had with aperture blades not working is with a Kiron lens that has oil on the aperture blades. I don't think that's probably your problem, but it's always worth checking out (you can see the oil on the blades).
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Old Sep 2, 2008, 8:16 AM   #4
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That's a pretty common problem (oil on them causing aperture blades to stick) with some lenses (it can happen with older Minolta 50mm AF lenses)

I know of some web sites showing how to fix this issue on some of the Minolta AF lenses that it can happen with. For example, Pete Ganzel has some instructions for taking apart some of those lenses, where you can click on a photo and see directions on each step.

http://www.pbase.com/pganzel/disasse...xxum_50mm_lens

If you read the forum posts below the album, you'll see comments from readers thanking him on helping to solve the sticky aperture blades issue after they took them apart and cleaned them.

There is probably someone that has put together similar pages for your lenses somewhere.
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Old Sep 2, 2008, 9:34 AM   #5
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Rio,
if the ap ring just turns and turns around the barrel it's because it's probably because the ring has slipped off a small cam in the barrel. this happened to me with a M50/1.7. you have to practically disassemble the whole lens to get to it. i can't say how the viv connects but it's probably close to the pentax. unfortunately i did not take pix when i fixed mine. here's how to get into a K-mount lens.
DISMANTLE

roy
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Old Sep 3, 2008, 4:06 PM   #6
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Thanks for all the suggestions. Mtngal, it's not that the iris blades are oily (I can't tell cause I can't see them) but that the aperture ring seems disconnected from the iris. Roy, the site on dismantling a Pentax lens may help with other problems; Jim, the site on dismantling Maxxum looks really useful now, since my problematic Vivitar lens seems built that way (disassemble from back), rather than the Pentax way (disassemble from front). I should have a chance in a couple days to try that. And I'll keep googling; maybe I'll get lucky and find some specs or schematics. Hoping...

--Rico
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