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09-07-2016, 07:12 PM   #1
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Pentax A* 600 F5.6 Loose Barrel

I had a question concerning this lens that I hadn't noticed until earlier this week that maybe someone can verify for me.

When taking the lens out of the case I noticed that the barrel seemed to be a bit loose, nothing too drastic, and it does seem to vary day to day. Holding the lens at the point on the barrel where the filter holder is and at the point of the white part of the barrel just past the focus ring (the areas shown with the red arrows in the photo) There is a slight play both side to side and front to back, it's small, less than 1mm I would guess. It makes a bit of a clicking sound, which is really how I first noticed that it is moving.



Once I attach a camera to the lens or mount it to a tripod / monopod the lens seems to tighten up and the movement is much less noticeable if even at all, (probably why I've never noticed it) so possibly the gravitational weight of the camera on the lens tube? Maybe it's the outside temps, I don't know. Focusing is even smoother with a camera attached so maybe it's by design. I checked all visible screws for tightness (mounting bracket, lens mount) but all were snug. I have worked on and cleaned numerous fixed focal length lenses over the years, and I was going to see if there was a way to tighten things up a bit, but as I've never worked on this lens I'm a bit hesitant. Before I dig into this, I want to make sure I actually even have a problem in the first place.

I was wondering if any of you who have this lens experience the same thing, and if not is there anyone out there who may have worked on this lens before that may be able to provide some insight.

It doesn't seem to affect the photo quality of the images, they are just as sharp as always, so I'm not too concerned, but if it's the beginning of an issue I'd rather take care of it sooner than later.

Steve

09-08-2016, 04:31 AM - 1 Like   #2
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Loose screws. My FA* 600/4 has been two times in for service to tighten screws. Now the barrels are loose again :-(
No. The screws are not on the outside of the lens...
09-08-2016, 05:52 PM   #3
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Looked at the lens a bit more this evening and I noticed that just the act of attaching my Manfrotto monopod by screwing it directly into the lens foot tightened the lens right up, no barrel wobble at all and silky smooth focus just like always. I can't see how that would have any effect on barrel wobble since the tripod collar is free moving, unless the screw was exerting pressure against the barrel somehow. So I tried screwing a couple of different quick release plates into the lens but none of them had any effect on the barrel wobble. Hmmm.....I'm beginning to wonder now that if I did somehow figure out how to tighten the lens barrel when the lens is unloaded that it might be too tight to focus with a camera and monopod attached.
09-10-2016, 08:29 AM   #4
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QuoteOriginally posted by Pål Jensen Quote
Loose screws. My FA* 600/4 has been two times in for service to tighten screws. Now the barrels are loose again :-(
No. The screws are not on the outside of the lens...
Pål,

I don't know why I didn't see your post until after I posted my follow up, but you are absolutely right, it appears that loose screws in the barrel forward of the focus ring is my problem as well. The lens 'sags' a slight bit at that point when on a tripod, no doubt from the weight of the forward glass pulling down on the barrel all of these years. Not sure I want to take this lens apart myself, so it looks like I might just have to send this one into the shop for a tightening.

Thanks,
Steve

09-10-2016, 08:56 AM   #5
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The angled ring just to the left of your leftmost arrow in the picture unscrews and will expose some screws underneath. (The "upsizing" ring -- what would you call that?) Don't know if those are the ones that need tightening. Just loosening that ring will introduce a slight bit of play.

Mine doesn't have the problem you describe but did develop (before I got it) and slight binding of the focus ring at the closer end (becomes harder to turn) -- some ring in there got squeezed and became misshapen I think. But similar to what you say about your wobble, it behaves differently depending on the position of the lens so gravity seems to affect it. Haven't been quite able to figure that out.
09-10-2016, 09:29 AM   #6
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Thanks for the tip, I'll take a look at the "upsizing" ring this evening and see what I find.
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