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06-17-2009, 12:06 PM   #1
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bwield's Avatar

Join Date: Mar 2008
Posts: 444
Vivitar 100mm 2.8 need fixing....

Well I sold this lens in the marketplace, and it seems that it must have been damaged in transit.
The problem?
Simply that it wont Stop Down.
When on the A setting the camera cannot make it stop down, and when I manually change the aperture nothing happens.
There is still the soft clicking when manually changing the F stop, but the blades do not close.

Is this something that can POSSIBLY be fixed easily?

06-17-2009, 01:08 PM   #2
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
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Posts: 4,873
I think this is a close relative of the Kiron 105mm f2.8 macro, right? Hope so, otherwise my advice is meaningless. The Kiron has two long arms that extend into the lens and move the aperture. They have to be long because the lens extends so much. Here's a photo:

This part is very easy to remove. Take out the four screws on the ring just above the aperture ring (where the PK/A label is in my photo) and it slides out. You may have to disengage a tab that fits into the long slot in one arm. The rear lens group is also easily removed at this point, so you can see the aperture right there.

The likeliest possibility is oil on the blades has stuck them wide open. The focus grease might have vaporized and gotten onto the blades in transit if the lens was subject to high temperatures. Otherwise, I don't know. One lever is moved by the stop-down lever in the camera and the other is moved by the aperture ring. Each lever controls distinctly different parts of the aperture mechanism.

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