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10-26-2020, 08:21 AM   #1
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Pentax A 20mm f2.8 problem.

I have the Pentax A 20mm f2.8. It's a great lens and works fine. However, the cowling (as I'll term it) into which a filter and/or lens hood screws, is a little loose. It does not spin, so I can use it for its purpose, but it allows the attached filter and/or hood to jump a little as the lens is used. I've pulled back the rubber grip on the focusing ring, and I see two flush screws in slots, which I take to be for infinity adjustment. Also there are three small set screws in the same ring. I am afraid to take it any further without some guidance. Anybody seen this ?

10-26-2020, 01:19 PM   #2
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I own a Pentax A 20mm F2.8 but do not understand exactly your problem.
Could you post a photograph of the cowling (filter screw thread)?
10-26-2020, 01:40 PM   #3
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The filter thread ring/barrel is usually held in place by three or more screws under the black plastic ring around the front element (no lettering on most "A" series lenses). Unscrew this ring and tighten the screws. You might need to find a rubber stopper or bottle cap covered with electrical tape that will fit inside the filter ring to help remove the plastic ring. Wearing rubber gloves sometimes works depending on how tightly the ring is screwed in.

Although not the same lens the basic construction of the barrel should be the same. Go to around 1:40 to see how to remove the plastic ring and access the screws.

10-26-2020, 04:06 PM - 3 Likes   #4
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Hi had this same issue with my A20 a few months ago. Remove the plastic ring (it's quite wide compared to other A lenses) with a rubber ring and tighten the three screws that hold on the focus ring. I've found the front of the A20 to be one of the easiest lenses to get apart.

10-28-2020, 01:48 PM   #5
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Thank you so much! Where do I get that rubber ring ?
10-28-2020, 02:18 PM - 2 Likes   #6
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QuoteOriginally posted by Petrock Quote
Thank you so much! Where do I get that rubber ring ?
That looks like the flush valve seal from an American Standard toilet.
10-28-2020, 02:20 PM   #7
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I have a set of six rings from Japan Hobby Tool. Search for "Vacuum pad camera parts and lens opener."
10-28-2020, 02:24 PM - 1 Like   #8
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QuoteOriginally posted by Petrock Quote
Thank you so much! Where do I get that rubber ring ?
I bought a set just last week from Japan Hobby Tools on Amazon... | Japan Hobby Tool Vacuum Pad Camera Parts Opener

Works well.



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