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08-17-2019, 12:18 AM - 1 Like   #1
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SMC Pentax-M 50mm f1.7 loose clicking noise inside

So I was wondering about this.

My SMC Pentax-M 50mm f1.7 works great, but when tilting the lens I can hear something loose inside, the sound is not rough - just a quiet *click* that sounds like something is loose.

It's not a loose screw; rotating the lens around its axis makes no sound - it happens only when tilting.

I have a DIY tool to remove the plate/ring with the writing, and last year (when I hadn't yet paid attention to any clicking) I had checked that the little screws right underneath the plate/ring are tight, but I never went further than that.

Not sure if this is something I should just leave be, or that could be fixed easily (I really like the lens and the feeling something could be off bothers me).

08-17-2019, 12:29 AM   #2
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It may just be a lens that is loose in it's mount, just in need of a little tightening. Use your finger nails to see if the rear lens screw is tight. It is a fantastic lens by the way.
08-17-2019, 12:46 AM   #3
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QuoteOriginally posted by arnold Quote
It may just be a lens that is loose in it's mount, just in need of a little tightening. Use your finger nails to see if the rear lens screw is tight. It is a fantastic lens by the way.
Thanks, it actually sounds just like that; like a lens element that has gotten loose in its mount. Quite annoying.

The rear lens appears to be tight, it won't budge.

How far in could I 'safely' go from the font - without ending up past the point of no return and messing up the calibration. I once opened an SMC zoom lens from the rear and it turned out to be a ride, involving tiny springs etc...
08-17-2019, 01:27 AM   #4
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Are you sure it comes from a loose lens element and not just a play in the aperture mechanism?
A play in mechanism is normal, especially on a lens that may be over 40 years old.

If you do not have any issues with the lens, I would not mess with it. There is always a risk that it gets worse after you have taken it apart.

08-17-2019, 02:00 AM   #5
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QuoteOriginally posted by Fogel70 Quote
Are you sure it comes from a loose lens element and not just a play in the aperture mechanism?
Well you're right, I'm not... I guess the sound kind of resembles a loose element (click-sound comes after the tilting reaches a certain angle) but I could be mistaken, too.
08-17-2019, 07:44 AM   #6
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If the focusing grease is completely dried out there can be some "play" in the focus threads. This can cause the lens barrel to "rattle" in the focus barrel as there is no grease to dampen out this play. Can you move the focus ring ever so slightly towards and away from body without twisting it? Or can you twist the ring ever so slightly back and forth without any resistance? You might just need to regrease the helical threads.
08-17-2019, 10:12 AM   #7
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Do you have a filter mounted on its snoot ? I have a couple lenses with crappy filters that "Click" when moving around....the glass is hitting the aluminum filter ring.....Just a thought
08-17-2019, 01:01 PM   #8
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QuoteOriginally posted by Not a Number Quote
If the focusing grease is completely dried out there can be some "play" in the focus threads. This can cause the lens barrel to "rattle" in the focus barrel as there is no grease to dampen out this play. Can you move the focus ring ever so slightly towards and away from body without twisting it? Or can you twist the ring ever so slightly back and forth without any resistance? You might just need to regrease the helical threads.
Hmm, I think that's a no.. The focus ring feels super (!) smooth and firm, there's appears to be no play in it.

The outermost metal part/barrel (the one that extends from the lens body when focusing closer) does move -very- slightly away and towards the body, but I'm talking a tenth of a millimeter and only when really pulling/pushing, overall the whole thing is super firm.

The part that sounds loose inside, clicks sort of like it's "lightweight" if that makes any sense. Like an actual loose part, although the noise is subtle.


QuoteOriginally posted by Ronald Oakes Quote
Do you have a filter mounted on its snoot?
Nope, no filter either I'm afraid...

08-17-2019, 04:14 PM   #9
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QuoteOriginally posted by film-love Quote
Thanks, it actually sounds just like that; like a lens element that has gotten loose in its mount. Quite annoying.

The rear lens appears to be tight, it won't budge.

How far in could I 'safely' go from the font - without ending up past the point of no return and messing up the calibration. I once opened an SMC zoom lens from the rear and it turned out to be a ride, involving tiny springs etc...
If you can unscrew the front nameplate, you may see some screws that have come loose and need tightening. Don't venture deeper unless you are confident you know the way back. You can unscrew the name ring by finding a jar with the same size mouth and putting double sided tape on the lip in order to grip the nameplate. Be very careful not to bend the name disc when later prying off the tape.
08-18-2019, 04:33 AM - 1 Like   #10
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QuoteOriginally posted by arnold Quote
If you can unscrew the front nameplate, you may see some screws that have come loose and need tightening.
Thanks, I did that and actually did find that a couple of screws were still loose! I tightened them.

This didn't fix the actual issue. However...


QuoteOriginally posted by Fogel70 Quote
Are you sure it comes from a loose lens element and not just a play in the aperture mechanism?
...I then also went in through the back and, indeed, the cause of the sound was play in the aperture mechanism.

There's a metal plate/circle in there, which makes a surprising amount of noise whenever the lens is tilted, even though the plate is secured as it should be. Maybe with this particular unit, the metal plate is ever so slightly too thin and has a little more room to breathe than usually.

I love the lens so it's great to know there aren't any actual glass elements wobbling about, I appreciate the help everyone.
08-18-2019, 07:29 AM   #11
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I just went and checked my three copies of the M 50/1.7......They all make a bit of "Ticking" or "Clicking" sound when handling them ! One is a little worse than the other two , but not by much.
08-18-2019, 10:32 AM   #12
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QuoteOriginally posted by Ronald Oakes Quote
I just went and checked my three copies of the M 50/1.7......They all make a bit of "Ticking" or "Clicking" sound when handling them
That's reassuring to hear Ronald, cheers!
08-18-2019, 11:14 AM   #13
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This question has come up before and my answer is that my very well-used M 50/1.7 does make a small click when tilted. So does my very lightly-used K 55/1.8 and many other lenses on my shelf. The M 50/1.7 has done so pretty much forever (~ 37 years), but so far, there is no functional problems.


Steve
08-24-2019, 09:06 AM   #14
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My Pentax-A 50mm f1.7 has something that makes noise when you tilt or shake the lens. Not so with A 50mm f1.4.

Then there are Kiron lenses with their dozens of ball bearings. I asked a Kiron rep about the rattling at a show back in the 80s. He had me talk to one of the techs who said it is normal. The tech said they found by leaving a few bearings out instead of packing it fully there was less friction - hence the rattle.
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