SDM Failure strikes again


fatspider

Link Posted 13/03/2017 - 10:54
My 16-50 is on the fritz, bought in November 2015 and it refuses to focus, tried it on the istD and the screw drive works fine. I thought Pentax had resolved the issue with the SDM and my new copy should have been OK, obviously not

Fortunately I got it from SRS so have the 2 year warranty, just waiting to hear back from them as to whether I send it to them or direct to Johnsons.

I did try it on both K5 and K3II bodies and also gave it a good screwing on the istD but it's not come back to life.
My Names Alan, and I'm a lensaholic.
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Nakedgun

Link Posted 14/03/2017 - 02:56
Not good news, at all.

My four SDMs were bought autumn 2014 and are without issues thus far, but I always worry.
"A republic, madam, if you can keep it." - Benjamin Franklin

fatspider

Link Posted 14/03/2017 - 13:32
Well it's getting dropped at the PO today on it's way back to retailer.

Hoping it's something simple like the AF/MF switch
My Names Alan, and I'm a lensaholic.
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fatspider

Link Posted 24/03/2017 - 11:38
10/10 For SRS and Johnsons.

Posted my lens back to SRS on the 15th got it back today 24th, fixed and working perfectly
It should have been back yesterday but Parcelforce were late.

Repair Note says: "Replaced and Calibrated Electronic Circuit Board, Replaced Mechanical Assembly"

One totally happy Chappy
My Names Alan, and I'm a lensaholic.
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davidstorm

Link Posted 24/03/2017 - 22:36
After some posts last year I'm now convinced the issue does not lie with the SDM Motor in these lenses. I strongly suspect it points to a capacitor (or capacitors) on the circuit board, which need to be charged in order for the motor to operate. If the lenses are left unused for periods of time, the caps lose charge and won't re-charge when fixed to the camera. We've seen loads of posts from people who use their SDM lenses regularly and don't have issues, whereas people who use them sparingly do.

I wish Pentax would come clean and tell us all what causes the problems and how to avoid them. My 50-135 will not work when first fixed to the camera, but after 30 seconds or so it does start working 100% normally, then I have no further issues. This lens has the latest motor.

Regards
David
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fatspider

Link Posted 24/03/2017 - 22:55
That's an interesting theory David, but how do you account for lenses that don't get a lot of use but are perfectly OK, my 50-135 is a prime example (finds wood to touch ) Also what about lenses that have sat in a warehouse or on retailers shelves?
My Names Alan, and I'm a lensaholic.
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wvbarnes

Link Posted 24/03/2017 - 23:11
Hi all,

I read a while back that the 16 - 50 and 50 - 135mm lenses had a potential design fault in that they had too tightly packed electronics thus subject to overheating. This could of course affect capacitors holding their charge as designed.

I've now sold my 300 F4 star lens for the more portable new 55 - 300 PLM zoom that suits my travel needs. The Star lens was a second hand 2008 model but nonetheless worked fine throughout a lot of use over several years. I've heard little of people having problems but presumably the same SDM system but more room for the circuit board?

RayB

Link Posted 28/03/2017 - 08:44
davidstorm wrote:
After some posts last year I'm now convinced the issue does not lie with the SDM Motor in these lenses. I strongly suspect it points to a capacitor (or capacitors) on the circuit board, which need to be charged in order for the motor to operate. If the lenses are left unused for periods of time, the caps lose charge and won't re-charge when fixed to the camera. We've seen loads of posts from people who use their SDM lenses regularly and don't have issues, whereas people who use them sparingly do.

I wish Pentax would come clean and tell us all what causes the problems and how to avoid them. My 50-135 will not work when first fixed to the camera, but after 30 seconds or so it does start working 100% normally, then I have no further issues. This lens has the latest motor.

Regards
David

There may be some mileage in this. I've got a 16-50 DA* purchased in 2011. A year or so back I thought it had died on me, but after being on the body a short time it sprang into life. Each time I've used it since then, I put it on the camera and wait a little while (not more than a minute, generally) and the lens is good to go. I know it's only one example, but to me it does suggest that the issues people have had may not all be drive related.

tyronet2000

Link Posted 10/04/2017 - 11:41
Note to self: Use the lens even if it's just indors or garden. Normal photography due to start end of April
Regards
Stan

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