Olympus-OM
[Top] [All Lists]

[OM] 28mm Lens Fix (Aperture)

Subject: [OM] 28mm Lens Fix (Aperture)
From: Chuck Norcutt <norcutt@xxxxxxxxxxxxx>
Date: Sat, 17 Nov 2001 08:25:56 -0500
David Matteson asked:
As I was looking over my gear last night I realized that the aperture
blades
on my Vivitar 28mm f2 lens do not move at all. They are completely
stuck...
What can I do to fix it? 
------------------------------------------
Hi, David
The first question is whether they're stuck due to oil/grease on the
blades or whether something is wrong with the linkage mechanism.  If the
blades are closed and won't open then it's probably oil or grease on the
blades.  The surface tension of the oil/grease is too strong for the
diaphragm return spring.  If the blades are completely open and can't be
moved you'll have to decide if the linkage has come detached or bent (in
which case the actuating lever should be free) or whether the blades are
so gunked up with dried oil/grease that the blades are stuck fast
instead of being just sluggish.

If the actuating lever has come detached or bent somehow you'll have to
open the lens from the back and figure out what happened by following
the linkage and cam mechanism.

If it's just grease or oil on the blades causing a sluggish mechanism
you can clean it off by using lighter fluid (preferably Ronsonol since
it's pure naptha and provides a useful spout).  You apply a couple of
drops of fluid, actuate the mechanism if you can to distribute the
fluid, then allow it to evaporate.  Then repeat, repeat, repeat until
the oil is cleaned off.

Ideally, one would remove both the front and rear lens elements to do
this.  However, removing the rear elements is more difficult since
you'll have to remove the aperture linkage also.  This will require some
tiny screw drivers and possibly dealing with tiny springs and maybe a
teeny-tiny spring loaded ball bearing under the aperture ring that
serves as a detent.  If you're careful, you can do it by removing just
the front elements.  By careful I mean being careful not to allow the
lighter fluid to drip past the diaphragm onto the rear lens elements. 
Even if you do drip onto the rear element you can clean it later when
the blades are open.

I don't know the construction of your lens but getting the front lens
group out usually means unscrewing it from the focusing collar.  To do
this you'll need a rubber friction tool to unscrew the "name ring" in
the front inside the filter threads.  You need something like a
furniture leg cup of the right diameter which has a grippy rubber
surface.  I use a wooden cup designed to hold a wooden closet rod.  It's
about the right diameter to fit inside 49mm filter threads.  The lip of
the cup has a strip of rubber band rubber cemented to it for a grippy
surface.

Once the name ring is off you will likely find that you will need some
sort of spanner wrench to unscrew the front lens group.  This could
require something with screwdriver-like flat blades or else pointed
pins.  You may be able to improvise a tool once you see the actual
arrangement underneath the name ring.  Careful though.  An improper tool
that slips or skips may damage your front element.  If the front element
does not unscrew easily it may be held in with some sort of "loc-tite". 
Then you'll have to experiment with a few drops of various kinds of
solvent to see if it can be loosened.  Try the lighter fluid or alchohol
first before going on to something like acetone which can damage plastic
and paint.

Good luck.  Feel free to ask any other questions.  I'll answer if I
can.  I've done this a few times with various lenses but I'm hardly an
expert.  I've also been defeated by one lens whose front group was so
thoroughly cemented in place that I couldn't get it out.  Perhaps the
list's resident repair folks will have some better advice.

Chuck Norcutt
Woburn, Mass.
--------------------------------------

< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >


<Prev in Thread] Current Thread [Next in Thread>
Sponsored by Tako
Impressum | Datenschutz