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11-21-2019, 11:03 AM   #1
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Join Date: Nov 2018
Posts: 22
problem pentax A 28mm f2.8

Hello everybody. I had already had problems with mushrooms with this lens, but I had solved them by removing it from the front. Today, instead, I tried to take pictures and discovered that the diaphragm didn't open and close. Consequently I thought to disassemble the back part in order to verify the problem. Here, the problem I solved it, but while I was removing the back cover, the spring contact of the selector "A" was released and jumped out. Fortunately I recovered both the spring and its metal cap, but I can't understand how it should be reinserted. I see that there is a small milling on the cap, and I am wondering if there was a seger ring in it. Can anyone give me confirmation?
Thank you in advance.

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11-21-2019, 12:14 PM   #2
Not a Number's Avatar

Join Date: Mar 2012
Location: Venice, CA
Posts: 7,675
The bracket/contact you have circled pulls out. The pin fits into the contact from the right hand side as is oriented in your photo. You sort of tilt the top of the pin to the right (as pictured) and the grooves engage with the contact and straightens out. I find it easier to assemble with the spring in place.

See the thread linked which shows how the contact assembled. If you use grease on the assembly make sure it is conductive or else you have to take it apart again to clean off the non-conductive grease.

Pentax-A 50mm f1.7 Aperture ring repair -

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