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09-14-2011, 05:23 PM   #1
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Pin stuck

I have an 85/1.9 with a pin that tends to get stuck when pushed down. Wanted to know if there is any DIY method to fix this?

09-14-2011, 05:49 PM   #2
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Do you mean the "Auto-Aperture" pin? The other question would then be, are the aperture blade showing oil?
09-14-2011, 09:11 PM   #3
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I have some pics of what I mean:




No oil on blades that I can note:







So, when the pin gets pushed down, it tends to stay that way for a good while, then it slowly comes back out.
09-15-2011, 03:15 AM   #4
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It does sounds as though something is getting gummed up and only in worst case, is a spring snapped. Since it does still come out sometimes, the most common issue is what I've encountered in this type, the grease goes waxy over time. It will cause the armature that is suppose to rotate to become sluggish and so the pin won't get pushed back out. In some designs, the aperture will still be quick and yet the apertures can't push back hard enough to reset the pin... in short, it needs a good cleaning.
I'm not blessed with a 85/1.9, but I could give some instruction for disassembly based other M42. Or, take a look at this site... PENTAX MANUALS

09-15-2011, 08:31 AM   #5
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Gosh, I am not a handy person, but I want to give this a go.
09-15-2011, 09:12 AM   #6
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You might want to ask Eric how much a cleaning would cost before trying a DIY.

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09-15-2011, 09:26 AM   #7
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Thank is true what BORISCLETO says think about Eric if you are not sure, otherwise, you need some quality screwdrivers to work on a nice lens as that.
09-15-2011, 11:04 AM   #8
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QuoteOriginally posted by boriscleto Quote
You might want to ask Eric how much a cleaning would cost before trying a DIY.
Here's some information to decide if you want to do it yourself. Edit: specific instructions to this lens are below in post #14.

The problem is probably simple to fix but hard to get to. Most of the Takumar M42 lenses have a mount that's solid like this. They come apart from the front. To get to the mechanism controlling the pin, you'd have to take off the trim ring at the front, then the filter ring, the focus ring, depth of field scale and aperture ring. Three screws under the aperture ring hold the mount on. Remove those and you can see the pin mechanism. A cleaning and drop of oil in the right place would probably fix it. Then reassembly, maybe clean and regrease the aperture ring, adjust for infinity focus and done. The photos in this post cover the first few steps with a similar lens:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/135293-s-m-c-t...ml#post1411835

There's a few other guides on the internet showing more steps, but once you get that far it's easy. The screws on a Super-Takumar are likely to be common/slotted. An eyeglass repair kit will have the tiny size for the grub screws holding the DOF scale on.

For DSLR use, it doesn't matter so it's not worth fixing. It's an opportunity to do some cleaning. The lens is worth quite a bit so you don't want a botched repair. Eric's cost shouldn't be that high. This lens was one of my first repair atttempts and I succeeded.


Last edited by Just1MoreDave; 09-15-2011 at 09:10 PM.
09-15-2011, 11:10 AM   #9
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QuoteOriginally posted by Just1MoreDave Quote
The screws on a Super-Takumar are likely to be common/slotted. An eyeglass repair kit will have the tiny size for the grub screws holding the DOF scale on.
The grub screws on my Taks are all common/slotted but the other screws are all JIS.
09-15-2011, 11:24 AM   #10
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QuoteOriginally posted by boriscleto Quote
The grub screws on my Taks are all common/slotted but the other screws are all JIS.
It's going to be a coin flip. My copy of this lens is from about 1964, so slotted screws rule. I've seen at least some slotted screws used even in K lenses; other copies of the same lenses use JIS. I read somewhere that ISO standards started influencing the changeover in the late 60s, but it didn't happen all at once.I have a mental image of huge parts bins at Asahi Optical, and assemblers using what they had around.
09-15-2011, 11:38 AM   #11
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QuoteOriginally posted by Just1MoreDave Quote
It's going to be a coin flip. My copy of this lens is from about 1964, so slotted screws rule. I've seen at least some slotted screws used even in K lenses; other copies of the same lenses use JIS. I read somewhere that ISO standards started influencing the changeover in the late 60s, but it didn't happen all at once.I have a mental image of huge parts bins at Asahi Optical, and assemblers using what they had around.
My Super-Tak 50/1.4 8-element from 1964 has JIS screws.
09-15-2011, 01:45 PM   #12
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If it was mine, I would soak a Q tip in lighter fuel and wet the pin, then work the pin in and out. The pin going through the base is the longest point of friction, and the easiest place to get small particles of dirt.
As long as the internal mechanism is free, cleaning the pin and it's bearing surface will probably work, unless it's a slightly bent pin ( not unknown ). But don't soak it, just wet it while holding the lens upright so the crap runs down the pin and not into the lens, and keep wiping the pin. Don't wet the pin and use canned air, that would blow crap into the lens.
09-15-2011, 08:41 PM   #13
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QuoteOriginally posted by boriscleto Quote
My Super-Tak 50/1.4 8-element from 1964 has JIS screws.
Interesting, I have not seen those screws in a lens of that age.

Anyway, one anecdote is only OK for politicians, not for science! So for proof, I offer 4 anecdotes.

First is two K55/1.8s. On the left, both kinds of screws, on the right, just JIS:


Next, a Super Takumar 135/3.5. I don't know its exact age but it's the 4/4 formula so it's the newer 135/3.5 formula. Another mixture:


The third lens is my Super-Takumar 85mm f1.9, with the old font style. So almost relevant to the topic.


Last, an SMC Takumar 55mm f2.0:


I still like my huge parts bin theory, but we'll never take enough lenses apart for a statistically significant answer.
09-15-2011, 09:08 PM   #14
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I just realized that getting to the other side of the pin mechanism is easier than my original instructions. Those would apply to something like a 50/1.4. For this lens, you remove the trim ring with the lens name on it, unscrewing it with a friction tool via the filter threads. Then you'll see something like this:


Remove the three screws that aren't in little cutouts, and the filter ring comes off. Then remove the other three screws. (Note that these have washers with them.) Then the whole optical assembly can be removed from the lens: front group, rear group and aperture. It's impressively heavy. Set that aside in a safe place and you're left with this:


That's enough access to the mechanism to see what's not moving right and fix it. When you reinstall the optics, the aperture pin on the optic assembly slides into that fork on the right. Put in the three screws with washers but don't tighten them yet. Now you can rotate the assembly to make sure that the blades disappear whjen the aperture ring is at f1.9, and close fully at f16. When that's adjusted, tighten the screws, put the filter ring back on and screw the trim ring back on.
09-16-2011, 05:17 AM   #15
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QuoteOriginally posted by Just1MoreDave Quote
Interesting, I have not seen those screws in a lens of that age.

Anyway, one anecdote is only OK for politicians, not for science! So for proof, I offer 4 anecdotes.

First is two K55/1.8s. On the left, both kinds of screws, on the right, just JIS:


Next, a Super Takumar 135/3.5. I don't know its exact age but it's the 4/4 formula so it's the newer 135/3.5 formula. Another mixture:


The third lens is my Super-Takumar 85mm f1.9, with the old font style. So almost relevant to the topic.


Last, an SMC Takumar 55mm f2.0:


I still like my huge parts bin theory, but we'll never take enough lenses apart for a statistically significant answer.
You're right, I just looked again and the Taks have slotted screws. Except for the S-M-C 35/3.5. That one has JIS. That was the last Tak I had open so that must be how I "remembered" it.

Super-Tak 50/1.4 8-element - slotted
Super-Tak 50/1.4 7-element - slotted
S-M-C Tak 50/1.4 - unknown (dented filter ring)
S-M-C Tak 35/3.5 - JIS
SMC Tak 55/1.8 - slotted

I am going on the assumption that lenses intended for export to the US had slotted screws while lenses intended for the home market had JIS.

All of the M-series lenses I've looked at have JIS screws.
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