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01-05-2016, 03:06 PM   #1
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DA*300mm SDM autofocus problem

Since last summer, I have been having an ongoing but intermittent SDM autofocus issue with my DA*300mm. While on a trip last summer, the autofocus quit entirely (at a particularly inconvenient time). During the trip, I could not get it to work again no matter what I tried. A few weeks after I returned home, I picked up the lens to check it one more time before deciding to have it repaired or converted to screw drive, and it was working again. Shortly after that, I was out of commission for several weeks with a knee replacement, and I didn't use the lens at all. Today, I picked it up again, and at first, the autofocus was not working. I tried manually focusing the lens while holding the shutter release part way down and it started working again. I have 3 questions.

1. Is this a more or less common problem with this lens? By "this" I mean the SDM going inoperative until you jog it by manually focusing the lens while partially depressing the shutter release.

2. Does anyone know if Eric Henderson will convert one of these lenses to screw drive? Is there another reputable repairman that will do such a conversion?

Let me explain my dilemma. I have a k-3 and a k-5. I realize the k-3 cannot be used to convert an SDM lens to screw drive. I want to sell the k-5, but am hesitant to do so unless I have an alternative to deal with the 300mm if the SDM quits entirely. OTOH, I don't want to mess with the lens if it is working.

01-05-2016, 03:17 PM   #2
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01-05-2016, 03:33 PM   #3
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QuoteOriginally posted by mechmike10 Quote
I realize the k-3 cannot be used to convert an SDM lens to screw drive.
If the lens has screw drive, it will work on the K-3, so if you get the SDM disabled on your DA*300, it will work on it too.
01-05-2016, 04:06 PM   #4
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I understand that. The problem is the k-3 cannot be used to do the conversion.

01-05-2016, 08:20 PM   #5
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Auto focus problem 16-50 2.8*

QuoteOriginally posted by UncleVanya Quote
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I currently have a K3 and would be interested if information is available to send off and have converted to screw drive. Thanks
01-06-2016, 03:26 AM   #6
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Hi, read this topic. I also had such problem a year ago and conversion was successful.
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/289060-da-3...s-problem.html
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