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06-02-2017, 05:49 AM   #1
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Sigma 17-70mm broken zoom ring?

Hey guys, I've got a nice Sigma 17-70mm f/2.8-4.5 lens that is still almost like new. All of a sudden, the zoom ring just turns all the way around, and doesn't "zoom" any more. If you shake it gently, you can hear a rattle inside, like a screw came out or something.

If I knew there was a chance that I could fix it, I would try my hand at taking it apart, but I've never taken an AF lens apart before. Do you think there's anything I can do for it?

06-02-2017, 07:01 AM   #2
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Original Poster
Thanks, @dcshooter, I bought it used, so I seriously doubt it's under warranty. From a quick search on the forums, it seems that this is not an uncommon problem with 17-50/70 zoom lenses. Has anyone ever successfully repaired one?
06-04-2017, 07:25 PM   #3
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Sigma sells parts to independent repairmen, so it should be easy to have it fixed for a decent price.
I repaired 3 different Sigma lenses during the last months, and I've been equally satisfied by Sigma's official service center, and by a local "approved" laboratory.
The advantage of using the "official" one lies in the fact that any lens they service is firmware updated. Sometimes that makes a huge difference...

From my own personal experience:
recent Sigma zooms are great, but they are way more fragile than they look!
A not-so-strong knock can bend the zooming and/or focusing sleeve, even if the exterior of the lens shows no visible damage.

There could be something loose in your zoom, but it's also possible that the part needs to be replaced.
In both cases the cost should be reasonable, cause it should be a quick repair.
I wish you good luck

Modern high cost Sigma zooms are just great, and from the way they look and feel you'd think they are well made, but I'm starting to believe that the Tamrons are actually sturdier.
I'm curious about the opinion of other Pentax users

Cheers

P
06-06-2017, 11:02 AM   #4
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I agree, Sigma lenses, even high-end ones, are not as sturdy as the look/feel.
Not awfully weak mechanics... but you got to be considerate, and treat the lens with some care.
Though i wouldn't be so sure the reason is production costs.
It could well be a design choice. Fast lenses, with large, heavy glass elements have strong inertia, and put some strain on AF in-lens motors.
Adding to the inertial force the weight of metal parts could increase the load, and be too close to the limit of the typology of electric motors used inside Sigma lenses.
Only a theory...

Regarding the software updates provided by Sigma (for free, together with bayonet exchange, for some lenses that have problems with the K-1), i already expressed my opinion.
Kudos to Sigma!
Their support is top level. PKAF lenses are everything but their core business, nevertheless Sigma is showing its commitment to the customers, all of them.
If i have to be totally sincere, i'd rather prefer to deal with a company that provides free service for lenses sold years ago, than with a company that doesn't even acknowledge the problem with SDM AF motors, let alone replace them (for free or at cost).
Don't get me wrong, i love my K-1, but since the switch to digital Pentax lenses are not what they used to be. Amen.

cheers

P

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