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Stuck aperture on Takumar!
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PostPosted: Thu Aug 12, 2010 8:42 am    Post subject: Stuck aperture on Takumar! Reply with quote

Hello,
My cherished S-M-C Takumar 28mm 3.5 has developed a stuck aperture. It moves normally from F8-F16 range but refuses to move past F8. It is also stuck on "automatic" (wont budge to manual). The automatic stop down mechanism still works though.

Please help!


PostPosted: Thu Aug 12, 2010 10:02 am    Post subject: Reply with quote

On camera end of lens in addition to long pin that operates diaphragm is another tiny pin; depress the tiny pin, the auto-man switch can move to man. Then while looking at diaphragm, slowly at first, stopping immediately if resistance is felt or diaphragm is seen to have folding problem, operate aperture ring full close to full open to work the diaphragm; blades may have only oil on them, the working may redistribute and thin oil blockage enough for proper opening. If stopped immediately because blades begin to deform, or working does not redistribute oil enough to restore full range, then disassembly and/or cleaning in in order.


PostPosted: Thu Aug 12, 2010 12:28 pm    Post subject: Reply with quote

the small pin visualopsins mentions should be pressed down when the lens is mounted, mounted it should move back to M, but of course you can press it with your fingernail too.

look at the back of my S-M-C 3.5/28, and see the pin:



in case you have to open the lens to fix the aperture you may find these helpful:
http://www.mypentax.com/tak50_1_4.html
http://camerarepair.wordpress.com/2010/01/18/takumar-super-multi-coated-353-5-disassembly/
http://homepages.ihug.co.nz/~Srawhiti/pentax50mmf1.4.html