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10-23-2018, 07:24 AM   #1
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FA 50 1.4 aperture blade fell off!

Very disappointing!

I have been using my Pentax F 50 f/1.7 for years and it has been a marvelous lens.
Recently, at the local swap-n-trade, I found a FA 50 f/1.4 for only $50 CAD!
Now, I tested this lens before I bought it. It was working perfectly: all apertures, all shutter speeds.

About 2 days later, I went to put the lens on my camera and I noticed that one of the aperture blades is floating around in there!

The blade has a little hole on the large end where it obviously is supposed to connect to something. It's not ripped or broken or anything.
I've found disassembly instructions for this lens, but it does not go far enough to show how to access the blades.
Since the lens only cost me $50, I might attempt to service the lens myself - unless someone can recommend a cheap alternative (Edmonton, Alberta, Canada).

Has anyone repaired the aperture blades on the FA 50 f/1.4? Do you have a link? Is it do-able?

Any advice?

Thanks!

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Last edited by FozzFoster; 10-24-2018 at 03:29 PM.
10-23-2018, 08:58 AM - 1 Like   #2
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I don't have experience with that lens, but aperture blade reassembly isn't too hard as long as you are patient and have steady fingers.

The tricks are:
1. Carefully removing and reinstalling the spring that helps close the aperture blades (without permanently stretching the spring)
2. Carefully opening the aperture blade assembly without flinging all the other blades on to the floor.
3. Carefully figuring out how to re-insert the loose blade on top of one neighbor blade but under the next neighbor blade.
4. Carefully closing the aperture blade assembly without one or more blades slipping off the posts that hold them in place.

Good luck!
10-23-2018, 09:01 AM - 3 Likes   #3
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QuoteOriginally posted by photoptimist Quote
The tricks are
Or to put it another way....it is like playing Jenga when drunk
10-23-2018, 10:21 AM   #4
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QuoteOriginally posted by pschlute Quote
Or to put it another way....it is like playing Jenga when drunk
But I have done it successfully. Re-fitting aperture blades that is, never tried Jenga when drunk.

10-23-2018, 11:36 AM   #5
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QuoteOriginally posted by pschlute Quote
Re-fitting aperture blades that is
Any advice for my adventure? Any links that show how to disassemble this lens or similar down to the aperture blades for servicing?
10-23-2018, 12:17 PM - 2 Likes   #6
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QuoteOriginally posted by FozzFoster Quote
Any advice for my adventure? Any links that show how to disassemble this lens or similar down to the aperture blades for servicing?
Only done it on an A-series lens. The complete aperture assembly came out easy as one unit then it was a case of dismantling and re-assembling the blades. This may help....

The F series will be different but the principles will be the same.

Advice...take pictures each step of the way and keep all the screws/parts separate.
10-24-2018, 07:24 AM - 1 Like   #7
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QuoteOriginally posted by pschlute Quote
The F series will be different but the principles will be the same.
Agreed. Most modern SLR lenses have very similar aperture mechanisms. They may vary a bit in how they're held together - sometimes a circular clip, sometimes screws, etc, but similar.

Getting it apart is easy. Putting the leaves back in is the hard part. Some lenses, I find, are best assembled by putting the blades into the part of the mechanism that's in the lens, and then lowering the cover over it. Sometimes you have to do it the other way round, assembling the blades into the cover, and then lifting it very, very carefully upwards into position with the lens pointing downwards. I often wonder how the factories manage to do it without all the trial and error.

The best types are where the whole aperture unit comes out of the lens intact. Much easier to set it up, put it together, and drop it back into the lens barrel. Mostly seen on old Canon FD's though.

The other week I worked on a Leitz 21mm for Leica R. For no apparent reason, the aperture blades were each two-piece items, hinged in the middle. Absolutely nutty, and mind-numbingly difficult to re-align.

I'm sure you'll have an easier time with the 50mm 1.4.

10-24-2018, 08:40 AM - 1 Like   #8
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Yep, I had this happen too. The blade didn’t fall off completely but it was dislodged such that the aperture was stuck at f/22 after being closed down. I had to send my copy to Erik Hendrickson for a CLA. He said it’s a fairly common fault of the lens. All was well after the CLA.
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