How to fix a sticky aperatue ring on the A 50mm F1.7

[Bob Tuttle]

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.

[filmamigo]

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

[maxwell1295]

Originally Posted by filmamigo

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.

[Tom M]

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'

[J.Scott]

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.

[filmamigo]

Originally Posted by Tom M

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?

[Tom M]

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.