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12-28-2014, 08:05 AM - 1 Like   #1
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SDM failure

I have a Pentax DA 50-135 lens that I purchased a few years ago. This lens has always worked great with no problems at all. About 8 months ago I purchased the 60-250 lens so the 50-135 has not been used recently. When I put the 50-135 on the camera it will not auto focus. Is there a way to "kick start" this lens?

12-28-2014, 08:37 AM   #2
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If you can mount it on a K100d or other Pentax bodies that don't have the ability to use SDM Lenses, it will work through the screw drive.
You may be able to free it up the SDM after exercising it for awhile.
You can also try this with the lens not mounted as well, but do NOT try to move the focus to the extreme ends. When you get near the end, stop and rotate back.

It is sad that such a great lens has these issues.

Good Luck.
12-28-2014, 02:44 PM   #3
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Even if you can get it kick started, when it is at that stage, it won't be long before the sdm fails completely.
That is what happened to mine, and I converted it to screw drive.
Focus actually seems a bit faster now, just a bit noisier.
12-28-2014, 03:30 PM   #4
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I would suggest trying the lens in liveview mode, if you have a body that supports LV.

Manually focus the lens to near correct focus and see if pressing the AF button (or half pressing the shutter) will restart the motor. The lens has two speeds of AF, and the slower speed (used when focus is nearer) seems more likely to promote a restart.

Good luck!
John

12-28-2014, 04:02 PM   #5
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QuoteOriginally posted by VladM Quote
Even if you can get it kick started, when it is at that stage, it won't be long before the sdm fails completely.
Yep, I'm afraid your lens' time has come. You'll have to decide if you want to convert it or repair it. A lens like the 50-135 is good enough to be worth the effort.
12-28-2014, 08:41 PM   #6
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Original Poster
Well, it appears that it is either convert it to manual focus or send in for repair. Thanks for the input. It is a very good lens, one that I would prefer to keep so it is time for a decision.
12-28-2014, 09:07 PM   #7
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Convert it to screw. A simple search will show you how.
12-28-2014, 09:47 PM   #8
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QuoteOriginally posted by wibbly Quote
Convert it to screw. A simple search will show you how.
Yes, that's what I meant. Convert it to screw drive. It already is manual.

12-29-2014, 09:38 AM   #9
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This problem does not seem to be the motor but the quick shift clutch sticking.My 16-50 lens does not get used much because of major use with prime lenses, check to see if the distance scale moves when you rotate the focus ring, if it does not change then its your quick shift clutch sticking. To remedy this turn your focus ring back and forth quickly until the distance scale moves fully. I have used this exercise many times because of lens not being used.Once I do this exercise the lens acts normal as long as you use it. Good luck.
12-29-2014, 10:09 AM   #10
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QuoteOriginally posted by BCtoad Quote
This problem does not seem to be the motor but the quick shift clutch sticking.My 16-50 lens does not get used much because of major use with prime lenses, check to see if the distance scale moves when you rotate the focus ring, if it does not change then its your quick shift clutch sticking. To remedy this turn your focus ring back and forth quickly until the distance scale moves fully. I have used this exercise many times because of lens not being used.Once I do this exercise the lens acts normal as long as you use it. Good luck.
Thanks! Will try that and see what happens.
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