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10-01-2006, 08:29 PM   #1
Arjay Bee's Avatar

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Tokina 28mm F2.8 M42 repair

Have a little homework project happening.
Picked this 28mm lens up at Cash Converters for not much. The aperture shutter only closes when I take the lens apart and move the actuating lever directly from the inside. The Auto manual slider works fine and the pin operates as it ought. Any help or pointers would be appreciated.

Does anyone have a 'how to' page on taking the aperture mechanism apart so that I can reassemble correctly? I don't want to adjust the focussing mechanism by mistake and make the problem worse. It does rattle a bit.

No fungus anyway and glass is in good order. The lens itself has average ratings as a unit but will allow better low light work at this focal length than currently held in lens collection.

On a positive side I bought a set of three m42 extension tubes that seemed to have a familiar knurl pattern on them. Get them home to find they are Pentax originals and they match the focus ring knurls on my Super Takumar 50mm 1.4. A very nice manual macro set now. Very happy.

10-01-2006, 09:30 PM   #2
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Hi Arjay.
Sometimes it's hard to find directions for repairing a specific lens. Here's a link for the disassembly and cleaning of the Super Takumar f1.4 50mm:
and here's one for the 35mm takumar:
I had some problems with a Pentax zoom lens, but since this guides are for primes, they didn't work for me. Maybe they will help you.

Good luck,
10-02-2006, 03:01 AM   #3
Arjay Bee's Avatar

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Original Poster
Thank you for those Robert.

Of the two the tak50 is most similar but sill very different. I suspect there is grease all over the blades as they are very sluggish and sticky - enough that the spring to not open them when the aperture is forced open even though the external setting is wide open. Will try some grease solvent tomorrow and see if it makes a difference. Even the writer of that article warns against opening up that mechanism. Visions of spring loaded blades and ballberings flying around the room immediately present themselves.

Again thank you for that help. Here is another site for those exploring this way of utilizing the dwindling supply of M42 glass
And renovating old Pentax cameras:

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