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Old Jul 5, 2008, 5:09 PM   #1
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I have a Sigma 70-300mm lens on my Sony Alpha, which I've had for over a year, and had no problem with. Today when i put the lens on and turned the camera on, this awful noise started and lasted about 3 seconds. Once the noise stopped, the camera will work and take photos, but they are totally out of focus, the auto focus won't work. this happens every time i try it out.

When i put my sony 18-70mm lens back on, there is no problem at all, so i know the issue is with the larger lens. ANybody have any idea whats goin on?
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Old Jul 6, 2008, 9:19 AM   #2
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Welcome to the forums.

The gears in the lens are probably stripped. I've seen multiple reports of this issue recently with the Sigma 70-300mm on newer Sony dSLR models.

It could be a bad batch of lenses. But, on the surface, it looks like the construction quality of the lens just isn't up to dealing with the higher torque focus motors in the new Sony dSLR models, and so the teeth on the gears are being stripped.

Which Sony Alpha model? The A100 has a slower AF motor compared to the newer models.

Note that any of them can fail though. For example, I've got an older Sigma 35-70mm f/3.5-4.5 AF lens in Nikon mount with stripped gears now.

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Old Jul 6, 2008, 9:26 AM   #3
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P.S.

I've moved your thread to our Konica Minolta / Sony Alpha dSLR forum (you posted this in our Sigma dSLR forum, which isn't designed for discussion about Sigma lenses). In the case of Sony dSLR models, the Konica Minolta / Sony Alpha dSLR forum is the best place to discuss lens issues with Sony, Minolta or third party lenses used on these models.

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Old Jul 7, 2008, 12:49 AM   #4
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It is stripped gears for sure. I am awaiting return of mine from Sigma for the second time. They have had it more than I have. It is less than 4 months old and it has happened twice now.
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Old Jul 21, 2008, 10:31 PM   #5
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Update, Got my lens back for the second time from Sigma last wed. Took it out thur and in 10 minutes I had a stripped autofocus gear again. Called Sigma talked to a technician who said send it back again, gave me a fedx account number so sent it back overnight. She said she would get a replacement for it this time, I sure hope so cause its going on fleebay as soon as they do.
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