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09-18-2011, 07:32 AM   #1
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Help: K 50mm 1.4 disassembly


I was wondering if any one has disassembled a K 50mm 1.4 before, and if so if you would mind sharing some tips. I've worked on M 50mm 1.7s, but the K is different.

If I go in from the back, I get the bayonet mount off, and the aperture ring off, then... that's it. There seems to be nothing else to remove, and I can't seem to unscrew the rear element group like I can on the M 50. Should the rear element group be unscrewable?

From the front, right now the front decorative ring is stuck, so I can't even get to any of the screws holding in the front elements.

My lens is in pretty good shape except for quite a large amount of dust and a hair, so I'd rather not do destructive experimentation on it. Any advice/resources regarding disassembly would be greatly appreciated.


09-18-2011, 08:30 AM   #2
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If I encounter a stubborn trim ring, I make sure the threads are in as good a shape as they can be. The filter ring should be round - check it with a filter. I use a toothbrush and Windex on the threads to remove any grit. Then I put a few drops of light machine oil on just the filter threads, set the lens with front element facing up, and wait. The idea is to have the oil run down the threads and loosen up the trim ring. You need the trim ring itself to be oil-free for your tool to get a grip. Too much oil might migrate to the aperture blades but it won't happen instantly; you can wipe up the excess. I hate to admit defeat and drill holes in the trim ring for a spanner. I'll just put the lens next to the computer and keep trying.

I can't find my photos of the rear of this lens, so I only have guesses there. No screws under the aperture ring?
09-18-2011, 10:41 AM   #3
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This work on one stubborn lens... not sure if it will help in your case? I found a plastic lid the same size as the trim ring and positioned two sided tape bits all around between words as I didn't want to damage the letters. Stuck the lid on and while the tape was chewing up from the turning, it was working to loosen it finally. This was only to loosen the ring and no more as the tape will smear into the lens at some point... yuck. Oh, the lens was a M50/1.4 that was seemingly super tight as if 'thread-lock' was applied?
09-18-2011, 10:50 AM   #4
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I didn't try it with K50/1.4 but I tried to take apart K50/1.2.
From the front it was no go, and from the back I got stuck when reaching iris blades and focusing ring.

To get there:
Remove bayonet, then take of aperture ring, rear element grop just unscrews out. If I remember corectly, then there is ring with distance scale that doesn't have any screws, it's just pushed in. Under is spring that opens aperture and last thing I managed toi undo (not that it would help me) was a little screw on focusing ring that acts as stopper at the limits of the fucusing range. I believe underneath all of this was just the aperture assembly but I didn't try to take apart that one as I was scared I'll never put it back together... That's as much as I managed but again, I ain't sure if K50/1.4 is the same...


09-18-2011, 04:34 PM   #5
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Thanks for all the tips so far. I'll try some oil on the filter threads and some kind of friction cylinder to try to get the trim ring to budge. For the rear, I was able to unscrew one element with the help of a rubber grip, but that's it; the rest of the rear group is still in there. But if I can get into the front I should be able to just open the aperture and clean the rear elements from the front. Thanks again.
09-19-2011, 10:28 AM   #6
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I've disassembled a K 28mm f3.5 completely, and K 50mm 1.4 partially. If you want to take them apart completely you have to go from both sides (unfortunately, since takumars are disassembled all the way from the front.) For grip on the front, I put a piece of tourniquet and them push it down with a roll of tape. Works pretty good for me.

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