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10-01-2017, 07:34 PM   #1
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DA* 50-135-- to fix or not to fix, that is the question...

Hi fellow Pentaxians,

I was out on a shoot earlier in the month and alas, my DA* 50-135 autofocus didn't work. I hadn't used the lens for a while but it had been fine at last use. When I got home I poked around the forum and saw that my problem was not unique, but my lens had succumbed to a known issue. I read up on a few strategies and mucked about with my lens (rotating focus ring and turning the camera on and off many times and depressing the shutter release many times), and brought the AF back to life. Then I didn't use the lens for a few weeks, and alas, the AF again was gone. Again I brought it back. The routine is getting old though- it takes about half an hour and chews through batteries. So now I have to decide whether or not to keep it as is, keep it and repair it or buy one used. So I'm that context I have some questions:

If you had your lens repaired for this problem, what did it cost and were you happy with the result?
Is there a list anywhere of serial numbers of lenses that had this problem, or a number after which the problem was corrected? (No point in buying a new version of the lens or s used version unless you can check).
My lens is off warranty and I'm wondering if pentax covered any of the cost of off warranty repairs for this issue.
Finally, since the problem seems related to non-use, I wondered if it might resolve by just putting the lens on an old body and setting it to shoot a few times each hour over the course of several days.

Any thoughts? Thanks in advance for your insights and wisdom.

10-01-2017, 09:21 PM   #2
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you can covert it to screw drive.
There are a few threads in the forums
10-01-2017, 09:29 PM   #3
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I've had this happen to my DA* 50-135mm lens. I got it back in action by forcing it to AF in live view mode.

These days I tend to leave the lens on one of my cameras and exercise it for 15 seconds every couple of days. Seems to keep the SDM failure gremlins away.

Regards

Chris
10-01-2017, 11:57 PM   #4
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I too subscribe to the non-usage theory.

I diary an exercise session for my SDM lenses to take place every two weeks, also to test fire my various flash guns, whether I've used them or not since the previous exercise session.

So far, so good.

10-02-2017, 01:19 AM   #5
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Mine went the same way, as did my 16-50 previously. The regular exercise theory worked for a while with the 16-50, but that even that eventually was taking longer and longer to get any reaction from the autofocus.

In the end I took the plunge and converted both to screwdrive using the advice and video shown in the second post. Took about 15 minutes to convert both and I now have two functioning lenses. I have kept copies of the original firmware downloads from each lens should I ever wish to convert them back, can`t see any reason why I should though.

Screwdrive is slightly noisier, just as fast and also as accurate as SDM.
10-02-2017, 04:05 AM   #6
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Hi, from my findings problem seems to be related to drying grease in clutch mechanism. All it takes to bring lens back to life is to use small screwdriver and turn little screw in the lens mount that is connected to screwdrive. Turn that screw back and forth few times until it feels nice and smooth and it should sort the problem. Also I would like advise not to use camera focus button to do that as extra load on the motor may well be responsible for killing sdm. Hope this helps.
10-02-2017, 02:36 PM   #7
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QuoteOriginally posted by JohnX Quote
I too subscribe to the non-usage theory.

I diary an exercise session for my SDM lenses to take place every two weeks, also to test fire my various flash guns, whether I've used them or not since the previous exercise session.

So far, so good.
I agree as well. With SDM it is use it or lose it! I regularly exercise my DA*200 and DA 17-70 and it keeps both of them working. Unfortunately I am not sure if the SDM on the 17-70 will hold up too much longer. Note all of this is specific to SDM, DC and PLM lenses do not need any of this. They are up and ready as soon as the camera is turned on.
10-02-2017, 09:39 PM   #8
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QuoteOriginally posted by jddwoods Quote
I agree as well. With SDM it is use it or lose it! I regularly exercise my DA*200 and DA 17-70 and it keeps both of them working. Unfortunately I am not sure if the SDM on the 17-70 will hold up too much longer. Note all of this is specific to SDM, DC and PLM lenses do not need any of this. They are up and ready as soon as the camera is turned on.
Thanks for all the great responses. Interesting no one has their lenses in for repair. I think I'll start with the least invasive strategy- screw tightening/ and progress to converting it to screw drive. Hopefully my 10-17 and da* 17-50 won't pack it in.

Again, many thanks.

10-03-2017, 11:07 AM   #9
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Check UncleVanya out, he recently converted my daughters DA*50-135. He had super fast turn around time and it is a little nosier but now focuses faster than with the SDM!

SDM to Screwdrive Conversions - PentaxForums.com
10-03-2017, 03:07 PM   #10
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QuoteOriginally posted by geek-girl Quote
Any thoughts? Thanks in advance for your insights and wisdom.
Here is my experience with my DA 50-135. The repair notes are from the service invoices. All repairs were done under warranty (two years in Canada), by Pentax Canada in-house, I believe.

Purchased in Canada (Henry's) December 2011.

January 2013: Lens will not autofocus; needs several minutes to 'wake up' by exercising AF and MF numerous times. Unable to lock focus near 135mm. Manual 'quick shift' gets stuck. Repair: Motor replaced; lens adjusted, cleaned, tested.

March 2013: AF fine adjustment inconsistent across the focal length range. Repair: AF system adjusted; cleaned and tested.

November 2013: Does not autofocus. Focus mechanism jammed or seized. Unable to focus manually. Intermittent loss of AF. Repair: Focus ring repaired; focus system adjusted; cleaned.

December 2013
: Will not lock AF near 135mm. Loud 'squeal' or squeak when autofocusing. Repair: Focusing ring repaired. Replaced motor. Repaired gearing and clutch cam ring. Focus system adjusted. Cleaned and adjusted.

June 2016: AF and MF jammed. I converted the lens to screwdrive. No repairs required. No problems since the conversion.

There are plenty of anecdotes about problems with this lens model, but no real definitive fix. Certainly, this forum is reporting far fewer 'SDM problems' than several years ago.

- Craig
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