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  1. #11

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    ccbob,
    Information only:
    There's no lube applied to any portion of the aperture blade system.
    There is lube in the focusing helical, and it has to be thin in order to autofocus.
    What's happening is the lube is heated and then either migrates to the aperture system or evaporates and condenses on part of the system. Because of the surface tension on the blades or blade operating ring/housing there's not enough muscle in the system to move it.
    What any technician will do is remove the blades & clean the blades/housing/ring reassemble & consider it fixed. Unless someone comes up with a lube that is of low viscocity that doesn't migrate this will continue to happen.
    Heavily sedated for your protection.

  2. #12

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    Quote Originally Posted by John Koehrer View Post
    ccbob,
    Information only:
    There's no lube applied to any portion of the aperture blade system.
    There is lube in the focusing helical, and it has to be thin in order to autofocus.
    What's happening is the lube is heated and then either migrates to the aperture system or evaporates and condenses on part of the system. Because of the surface tension on the blades or blade operating ring/housing there's not enough muscle in the system to move it.
    What any technician will do is remove the blades & clean the blades/housing/ring reassemble & consider it fixed. Unless someone comes up with a lube that is of low viscocity that doesn't migrate this will continue to happen.
    Thanks for the detailed info, John!

    One thing that still puzzles me though is why can't I change the aperture manually by rotating the ring? In my case, the ring will rotate freely and I can hear/feel it clicking at the marked f-stop detents, but the aperture itself remains wide open.

    Bob
    Bob

  3. #13
    erikg's Avatar
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    That is how it was expained to me, John. I had my lens cleaned by Nikon and later by a local repair shop that I trust. I was told that this can happen if the gear gets left in a hot car etc. which I would almost accept if it weren't for the fact that this lens lived a comfy life in a climate controlled Museum! No one had any answers for that so I just gave up. It's the only lens I've had that had this issue. Hope the lens in question has a better fate.

  4. #14

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    ccbob,
    The aperture won't close because the lube holds it in place in the housing.
    The aperture ring has a tab that is used as a stop, when the camera stops the lens down, the blades are pulled to the stop by a spring. The spring doesn't have enough oomph to overcome the tension of the lube.
    Heavily sedated for your protection.

  5. #15

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    Quote Originally Posted by John Koehrer View Post
    ccbob,
    The aperture won't close because the lube holds it in place in the housing.
    The aperture ring has a tab that is used as a stop, when the camera stops the lens down, the blades are pulled to the stop by a spring. The spring doesn't have enough oomph to overcome the tension of the lube.
    John,
    Thanks for the further clarification.

    The lens is currently on its way to Nikon. Hopefully I won't be repeating this in another 6 months.
    Bob

  6. #16

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    Bob,
    It may be too late, but if I were in your shoes I would attempt to invoke my state lemon law to get a replacement. Something in that lens is out of tolerance to alow the lube to leak out. I've been shooting nikons since the early 80's and I've owned the 20/2.8D for over 5 years - its always mounted on a body. I've never seen problems like you are seeing with any of my lenses. My bags often sit for weeks locked up in vehicles in the south and mountain west 0 to 140 or more degrees with no lube leakage or aperture hanging.

  7. #17

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    Quote Originally Posted by nyoung View Post
    Bob,
    It may be too late, but if I were in your shoes I would attempt to invoke my state lemon law to get a replacement. Something in that lens is out of tolerance to alow the lube to leak out. I've been shooting nikons since the early 80's and I've owned the 20/2.8D for over 5 years - its always mounted on a body. I've never seen problems like you are seeing with any of my lenses. My bags often sit for weeks locked up in vehicles in the south and mountain west 0 to 140 or more degrees with no lube leakage or aperture hanging.
    I'm not sure that 3 instances in 18 months would meet the lemon-law criteria (not that I'm terribly up to date on such criteria anyway). I guess it's something that I can look into... guess I'm kinda hoping that Nikon, noticing that this is a recurring problem, will simply replace it themselves.
    Bob

  8. #18
    Mike Kovacs's Avatar
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    When you send it back to Nikon, insist that they replace the lubrication on the helical. Often times, in the name of efficiency (cutting corners), repair techs will clean the aperture mechanism but leave the old helical lube in place.

    The grease is separating into its native components (basically soap and oil), and the oil is migrating everywhere. The aperture blades are the most sensitive to the presence of oil but it will migrate anywhere it can, including onto the optics. That can cause fog, provide food for fungus, etc.
    If it says Zeiss or Rollei, the answer is YES!
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  9. #19

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    Quote Originally Posted by Mike Kovacs View Post
    When you send it back to Nikon, insist that they replace the lubrication on the helical. Often times, in the name of efficiency (cutting corners), repair techs will clean the aperture mechanism but leave the old helical lube in place.

    The grease is separating into its native components (basically soap and oil), and the oil is migrating everywhere. The aperture blades are the most sensitive to the presence of oil but it will migrate anywhere it can, including onto the optics. That can cause fog, provide food for fungus, etc.
    Thanks, Mike.

    I'll have to dig up an old repair statement and see what they've done in the past (assuming it's that detailed).
    Bob

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