Chuck,
This is great, thank you
Vick
On 20/07/2013 6:22 PM, Chuck Norcutt wrote:
> A sticky diaphragm usually means that the grease from the helical has
> broken down into a thick oil. It flows along inside the lens until it
> gets to the diaphragm blades. The thick oil causes the blades to be
> sticky. Then can be just sluggish or frozen open or closed.
>
> Since the blades are snappy when using the camera's activation lever
> (the inner tab) the blades do not have oil on them which is very good
> news. Using the DOF tab, however, does nothing other then press on the
> same aperture lever used by the camera but inside the lens rather than
> outside. If you watch the inner tab while you press the DOF tab you
> will see that both move together.
>
> Since only the DOF tab operates sluggishly it means that the problem is
> only in that linkage. The DOF tab presses on a semi-circular ring that
> is about half the circumference of the lens. It pivots on a single
> screw not far from where the DOF tab contacts the ring. Sluggish
> operation would seem to mean a loose screw, dirt or maybe even oil on
> the ring. In other words it likely needs a screw tightened or simple
> cleaning. Fortunately, it's very easy to access. I copied some repair
> text from an old message from Don Gaiken...
> -----------------------------------------------------------------------
> ...remove the three silver screws from the mount. The rear mount will
> just slide off. There are two tabs sticking out of the inside of the
> mount. One goes into a fork attached to the aperture's cam ring. The
> other actuates the aperture - it's spring loaded. To reassemble, just
> align the free tab (the one that's not spring loaded) so it will go
> between the legs of the fork, then turn the mount so the screw holes
> line up. Turning the aperture ring on the front should move the tab
> sticking out of the back of the lens both ways. If it only goes one
> way, try again - you've missed the fork. And when you move the aperture
> lever on the back of the lens, the diaphragm should close - if not, try
> again - you're on the wrong side of the lever!
> ------------------------------------------------------------------------
>
> Chuck Norcutt
>
>
>
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