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11-20-2007, 01:09 PM   #1
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How to fix a sticky aperatue ring on the A 50mm F1.7

I found this fix that seems to work, but be careful to not lose any parts. If you put this in your search engine 'pentax aperture ring fix' you may come up with some more info.

"Anthony Armstrong, Dec 17, 2003; 10:14 a.m.

I had exactly the same problem with a Pentax 50mm A f1.7. It is easy to resolve by unscrewing the lens mount and lifting off the aperture ring. (Put lens cap on and place face down on a folded towel first). Watch out for the little spring, tiny L shaped plate and even smaller ball bearing to pop out - you will want to put those back if you want the aperture ring to 'click' at the f-stops. You will probably find the the two little spring 'plates' that act as 'locks' to the "A" button, are both intact but the little plastic ridges they rest on are worn or broken so it is almost impossible to repair to origional functioning. No problem, just throw away one, or both, of the spring plates and reassemble. (I often 'stick' the little ball in place with the tiniest dab of silicon grease to hold it while reassembling). With the springs removed you won't have to press the little button to shift from, or into, the "A" setting on the aperture ring, so it can get accidentally knocked out of the "A" setting more easily. Personally I'm always switching from "A" to a specific aperture about every other shot so I actually prefer the lens without the button lock on "A". It sounds more difficult than it is - good luck.


02-08-2008, 09:37 AM   #2
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Hi Bob, thanks for the info.

Can you describe exactly what was wrong with your aperture ring?

I have a 50/f2 A that works fine, EXCEPT for the last click between f/2.8 and f/2. It takes a little too much effort to get there, and it feels like it's binding.

I wonder if it's the same thing and can be fixed the same way?

Dave
02-08-2008, 02:25 PM   #3
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QuoteOriginally posted by filmamigo Quote
Hi Bob, thanks for the info.

Can you describe exactly what was wrong with your aperture ring?

I have a 50/f2 A that works fine, EXCEPT for the last click between f/2.8 and f/2. It takes a little too much effort to get there, and it feels like it's binding.

I wonder if it's the same thing and can be fixed the same way?

Dave
My guess is that you have the same issue, only the wear on yours is on that one spot. The ring I have on my A50/1.7 is like that throughout the entire range. I shoot manually with the ring in "A" position, so it's not too much of an issue for me.
02-08-2008, 06:34 PM   #4
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The only thing I've ever encountered is that the lens wants to 'leave' it's largest aperture. They won't do it on their own but, some of my older M lenses will gladly jump to the next smallest aperture from the largest with the slightest of nudges.

Coincidentally, these lenses resolve better at that smaller aperture.. I think of it as the lens is 'snuggling into it's happy place'

02-09-2008, 07:54 AM   #5
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The older Pentac SMC lenses are very simple to open up and clean. All you need is a set of fine tipped screwdrivers - a #1, #0 and #00 Phillips - and a little patience. If you are unsure just take pics of each process as you go along. Work in a clean environment, use lighter fluid on a fine tipped paint brush to clean the metal parts, have a can of compressed clean air and some clean, soft cloths. Work slowly and gently and you should be fine.
02-09-2008, 10:05 AM   #6
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QuoteOriginally posted by Tom M Quote
The only thing I've ever encountered is that the lens wants to 'leave' it's largest aperture. They won't do it on their own but, some of my older M lenses will gladly jump to the next smallest aperture from the largest with the slightest of nudges.

Coincidentally, these lenses resolve better at that smaller aperture.. I think of it as the lens is 'snuggling into it's happy place'
You put it very well. That's exactly what this lens feels like.

Were yours always like that? Or would a cleaning help?
02-13-2008, 06:11 PM   #7
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well, they've been like that for a while, can't remember if they were always like that. Not sure if it's worth fixing.
12-17-2009, 09:52 PM   #8
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I've searched and found other threads where people ahve attemptd to fix this and were not successful. I found one on ebay and went to check it out locally to avoid shipping and it had this problem - how sure is this fix?

12-17-2009, 10:44 PM   #9
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It's a little easier, because what you really need to do is get the lens in A mode. Once it's there, it can stay there. If you want to use the aperture ring, get an M.

Here is a good description of the process, except he had better luck with reassembly than I sometimes have:

Pentax 50mm lens fix

When you reassemble the lens, you slide the aperture ring partly on, tuck one of those metal springs under it, slide it on more, tuck the ball bearing under it, slide more and tuck the final spring under. Then it goes on fully.

I think you can leave out the metal spring tabs and still end up with a lens that works as the first post suggests. The ball bearing is sort of optional too; it just makes the aperture ring click between stops. If you never move the ring from A, it's not useful. Resale value is less, though.
12-18-2009, 06:56 AM   #10
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I have a slightly different problem with this lens; the "A" setting does not work any more. I can move the aperture ring to the A setting, but the camera does not seem to recognize that it is on this setting. This didn't bother me much with my older cameras but now that I'm back into the SLR world with a new K-x I think it would be nice for this setting to work.

Any thoughts on how to fix this issue?
12-18-2009, 11:08 AM   #11
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QuoteOriginally posted by Nameles Quote
I have a slightly different problem with this lens; the "A" setting does not work any more. I can move the aperture ring to the A setting, but the camera does not seem to recognize that it is on this setting. This didn't bother me much with my older cameras but now that I'm back into the SLR world with a new K-x I think it would be nice for this setting to work.

Any thoughts on how to fix this issue?
Look at the mount of your lens when it's off the camera. With the A position and red dot at 12 o'clock, there's a small ball-bearing-like thing on the mount at about 5 o'clock. It's between two plastic circles on this lens. When you move the aperture ring into the A position, the "bearing" should stick out. At any other position, it should retract at or below the level of the mount.

The site I linked to has good photos of how this looks disassembled. The basic idea is, the protruding "bearing" makes a connection between a recessed connector on the camera and the lens mount. The camera recognizes that the lens is in A position and reads its aperture range (the plastic plugs do this). Somewhere, your connection is broken.
12-19-2009, 12:03 PM   #12
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QuoteOriginally posted by Just1MoreDave Quote
Look at the mount of your lens when it's off the camera. With the A position and red dot at 12 o'clock, there's a small ball-bearing-like thing on the mount at about 5 o'clock. It's between two plastic circles on this lens. When you move the aperture ring into the A position, the "bearing" should stick out. At any other position, it should retract at or below the level of the mount.

The site I linked to has good photos of how this looks disassembled. The basic idea is, the protruding "bearing" makes a connection between a recessed connector on the camera and the lens mount. The camera recognizes that the lens is in A position and reads its aperture range (the plastic plugs do this). Somewhere, your connection is broken.
Well, that's my problem... there is no protruding bearing. I took the ring off and it's not there at all. I guess I'm out of luck unless I can find another lens to steal parts from.
12-19-2009, 08:21 PM   #13
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QuoteOriginally posted by Nameles Quote
Well, that's my problem... there is no protruding bearing. I took the ring off and it's not there at all. I guess I'm out of luck unless I can find another lens to steal parts from.
Pentax seemed to enjoy making each lens and camera without interchangeable parts. I'm not sure if any other lens has the exact part you need.
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