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02-08-2013, 09:08 AM   #1
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I took apart my lens...

and it was such a great idea...said no one, ever! Actually it WAS fun and informative. It was a used old sears 50/1.7 with fungus. I finally got into the area where the fungus was and cleaned it out. For days I couldn't remember how to put it together... and I even took notes taking it apart. I think I've got the pieces in the right place now with a few exceptions that I'm looking for help with:

1. As soon as I opened the back the little ball bearing fell out and I don't know where it goes? I know it is for the aperture ring, but where?

2. The focus ring doesn't spin Any ideas what I did wrong there?

3. The final front element was really hard to open and now that it did open, I'm worried it isn't going to stay in place, nothing is really holding it there like most the other pieces.

Thanks for any help/ideas

02-08-2013, 09:16 AM   #2
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The little ball bearing was to lock the aperture ring in each place (I took one apart too). No idea on the rest.
02-08-2013, 10:14 AM   #3
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Join Date: Feb 2007
Location: Aurora, CO
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The ball bearing is trapped between the aperture ring and the rest of the lens. On a Pentax lens, there's a hole with a spring inside, in the lens body. The spring puts pressure on the bearing to hold it against the aperture ring. Here's a Pentax-M 50/1.7. The bearing is just above the orange diamond, stuck on with grease here. When it falls off, all you see is a hole.

The aperture ring usually has teeth on it that make the ring click at each stop. The teeth show where the bearing should be, so if you have the ring in the right place, the bearing should be opposite those teeth. Here's the ring and the teeth from the same lens:

I've seen one other arrangement where the teeth are parallel to the lens mount, not on the side.

I have no experience with that Sears lens. The front element may have been held in by tiny set screws on the side that you didn't see, and you forced it off. Now those scfrews are ineffective so it seems loose.
02-08-2013, 01:16 PM   #4
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Awesome, thanks for the photos! I don't think there were screws in there on that front part. Just a little piece where I had to use a spacer wrench to remove it and it was pretty well stuck there and now it just isn't as stuck. Makes me nervous that I'll tip the lens forward and boom it falls.


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