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06-25-2017, 09:28 PM   #1
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AF failure - SMC Pentax-FA 645 150mm F2.8

Hello,

I was shooting today and suddenly my lens stopped auto-focusing.

The motor will wind, though no change. Interestingly, the motor drive will wind in short intervals when trying to focus on something close and wind continuously when trying to focus on something in the distance.

Manual focus works fine. I've switched to my 35, 55, and 120 and all function as expected.

I've taken the battery out, i've engaged and disengaged the MF clutch several times. Still no response. Just the motor winding.

I have tried looking for information on the web and on the forum. The closest article I've found is and article from here back in 2012 regarding SDM lens AF failures.

Has anyone experienced something like this?

I thought it may have been due to heat, though it's been resting for hours in a cool environment with no change.

Any insight or suggestions are appreciated. I'm mentally preparing to have it serviced, though hope maybe its something mechanical that can easily be dis- or re-engaged to return functionality.

Regards

06-25-2017, 09:42 PM - 1 Like   #2
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I once had a 645 FA lens that stopped focussing, it had had a knock, and something inside had been misaligned. Was easily repaired by someone (whose name I don't recall, this was 4-5 years back).
06-26-2017, 12:54 AM - 1 Like   #3
Ole
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Your lens has no built-in motor, so SDM failure is out of the question. As Smolk indicates, it is most likely a mechanical failure.
06-26-2017, 02:10 AM - 1 Like   #4
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It shouldn't be too complex of a repair, and I'd expect most repair shops to be able to handle it. Eric should be able to do it (see the sticky in the repairs forum).


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06-26-2017, 05:38 PM   #5
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Thank you, all.

Adam, it seems Eric no longer repairs lenses (at least this type), due to inaccessibility of parts from Pentax.

I'm going to check some of the others listed on the sticky. Really appreciate the guidance everyone.
06-26-2017, 05:42 PM - 1 Like   #6
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QuoteOriginally posted by simianminded Quote
Thank you, all.

Adam, it seems Eric no longer repairs lenses (at least this type), due to inaccessibility of parts from Pentax.

I'm going to check some of the others listed on the sticky. Really appreciate the guidance everyone.
Good to know. Minimally, Precision should be able to fix it then, since the lens is considered current and still available new.

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06-28-2017, 05:57 PM   #7
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Mine did not need a new part.
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