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05-03-2021, 04:35 PM   #1
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S-M-C Takumar 28mm f/3.5 loose Auto/Manual switch


One of the screws holding the A/M switch in place on my Takumar 28/3.5 came loose and was rattling inside the aperture block.
I disassembled the lens but it appears that the screw just turns in place, there isn't anything securing the switch.
Before I disassemble the lens even further, I thought I'd ask: has anyone seen this before?
(excuse the poor quality of my microscope camera)

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Last edited by kcobain1992; 05-04-2021 at 09:14 AM.
05-03-2021, 07:14 PM   #2
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I can't say too much, having never taken mine apart, except to mention that the lens looks like it has been messed with.

BTW...good to see you post again. It has been awhile.

05-04-2021, 09:35 AM   #3
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I would have to agree that it looks like it has been messed with. When I discover that I usually conclude that it is a job for an actual pro unless it is something cheap and easy to replace. I am handy with tools and with some competency I can take things apart and get them back together without issue or having it look like it has been messed with. Which is why if I discover that something has been messed with I just assume the previous tinker screwed it up and I would need to know how it is suppose to look/work before taking it apart.
5 Days Ago   #4
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Original Poster
Thanks for the warm welcome.
I'm pretty sure this lens hasn't been messed with, since I've owned it for the better part of 10 years now, and it definitely did not behave like this when I first got it (actually it was the whole shebang, with leather case and square hood, and it was unused; it is definitely not unused now).
I guess what made you say that it looks messed with are the slight marks left in the slot screws. Those are left by my screwdriver, and a reason why I don't like slotted screws in the first place. Photos taken with a microscope aren't too flattering, either. Anyway.
Neither of the two screws could be fully and tightly screwed in place, it seems, not just the one that managed to fully unscrew itself. So I unscrewed them both, removed the Auto/Manual switch, and tried to see if the screws can at least be screwed in the switch's holes with no metal piece from the lens in between (at that time I thought the screws were too short and they aren't biting properly into the switch piece's thread). But surprise, they would not sit screwed tightly directly into the switch either. So I figured, what had happened is that due to mechanical wear, the switch's screw threads had become slightly chewed and would no longer take a screw snugly.
5 minutes of online research shows that the universal consensus is to drill another, slightly larger hole with a fresh thread, which I was unwilling to do (not only because the part is so small, but also because I would have had to enlarge the hole of the lens assembly itself, since the screw passes through that first).
So I picked up my Pentax ME body for spares, and after a few "nope, not this one", I managed to find a set of 2 screws that were ever so slightly larger in diameter than the 2 original slotted screws, and would fit absolutely perfectly. As an added bonus, the new screws are cross headed too.
Case solved.


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