DA* 50-135 SDM autofocus problems.


grahamcoad

Link Posted 28/10/2013 - 15:12
Some time ago I bought a Pentax DA* 50-135mm lens through Ebay. The seller advertised it as being perfect optically and cosmetically but with a slow, hesitant and erratic autofocus.

Naturally I was able to get it at a very good price, and have used it as a manual focus lens..

Recently I had some funds spare so sent the lens off to Pentax UK's servicing people who got the lens back to me well packed in about ten days, having fitted a new SDM Motor and PCB (Printed Circuit Board?).

I now have a 50-135mm that looks and functions like a new one.
Pentax charged 180 which includes postage, packing and VAT.

I think 180 was a fair price for this repair on what is a 900 lens new, service was quick, and it may be a help to anyone with a similar issue worried about the cost.
K-1, Sigma 12-24mm DG EX, Sigma 24-70mm DG EX, K-3, White K-01 with 40mm XS and white 35mm f2.4, SMC Pentax FA 1.8 31mm AL Limited, 43mm f1.9 Limited, 77mm f1.8 Limited, Sigma 17-50 f2.8, SMC Pentax DA* 50-135 f2.8, MX + SMC M 50mm f1.4, SMC A 50mm f1.4, SMC A 50mm f1.2, Spotmatic F 55mm f1.8, ES with 55mm f1.8 and 28mm f3.5, Program Plus (Chrome) with SMC A 50mm f1.7, Pentax 6x7, Leica ii, plus misc. odds and sods)

Gravelrash

Link Posted 28/10/2013 - 15:33
I was interested but never asked so the info is appreciated
Steve

Sometimes I'm serious and sometimes not, but I consider sarcasm an artform. Which is it today?

cabstar

Link Posted 28/10/2013 - 20:23
If you quoted Pentax user you would have got 20% of the price of repair if it was johnsons who repaired it
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Currently on a Pentax hiatus until an FF Pentax is released

sandinista

Link Posted 28/10/2013 - 20:30
That's good to hear Graham, thanks for the info. I have a very erratic 17-70 sdm lens and I might consider going down this route to get it repaired, it works just fine manually
Great simplicity is only won by an intense moment or by years of intelligent effort. T.S Eliot

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grahamcoad

Link Posted 28/10/2013 - 21:10
cabstar wrote:
If you quoted Pentax user you would have got 20% of the price of repair if it was johnsons who repaired it

It was, and I forgot...Please, no-one else make that mistake!
K-1, Sigma 12-24mm DG EX, Sigma 24-70mm DG EX, K-3, White K-01 with 40mm XS and white 35mm f2.4, SMC Pentax FA 1.8 31mm AL Limited, 43mm f1.9 Limited, 77mm f1.8 Limited, Sigma 17-50 f2.8, SMC Pentax DA* 50-135 f2.8, MX + SMC M 50mm f1.4, SMC A 50mm f1.4, SMC A 50mm f1.2, Spotmatic F 55mm f1.8, ES with 55mm f1.8 and 28mm f3.5, Program Plus (Chrome) with SMC A 50mm f1.7, Pentax 6x7, Leica ii, plus misc. odds and sods)

cgproudfoot

Link Posted 30/04/2014 - 18:23
Seems to be a common problem! Have just sent my DA*200 to Johnson's with the same problem - erratic and slow autofocus. Price 150 + VAT. Should get it back within 10 days. Hopefully the repair will last a while!
Chris

gtis

Link Posted 30/04/2014 - 18:43
Hi
I had a sdm failure on a da* 50-135 and sent it off to johnsons for repair
If you join pentax user plus at 10 per year as I did I got it repaired
For 144 including vat and return posted
cheers Neil
pentax k3 k5 super A
DA* 300 f4 DA* 50-135 f 2.8 smc DA* 16-50 f2.8 50mm f1.7 af 360 fgz pentax1.4xhd converter
sigma 17-70

Pentax o-gps1


Panasonic Dmc Fz200

cgproudfoot

Link Posted 30/04/2014 - 19:01
Thanks, Neil, but I've already paid, so I guess I'll need to remember when my next SDM fails
Chris

Mike-P

Link Posted 30/04/2014 - 19:13
cgproudfoot wrote:
Seems to be a common problem! Have just sent my DA*200 to Johnson's with the same problem - erratic and slow autofocus. Price 150 + VAT. Should get it back within 10 days. Hopefully the repair will last a while!

Unusual for any of the primes to have SDM problems, the 16-50mm and 50-135mm are the main culprits. My 16-50mm has had hesitant AF for years but has (so far) always sprung into life with a little coaxing.

It will probably die completely after me saying that, talk about tempting fate.
No equipment list here but thanks for taking an interest. My Flickr

grahamcoad

Link Posted 30/04/2014 - 19:37
If you drive an older vehicle, worth only...say 1000, but it needs 180 spent on it to last another few years, it seems sensible, and good value.

Strange then that people owning a 1000 lens baulk at paying 180 or so for the new updated SDM motor and sensor?

They should return the lens to 'as new' (or better) performance and last several years........
K-1, Sigma 12-24mm DG EX, Sigma 24-70mm DG EX, K-3, White K-01 with 40mm XS and white 35mm f2.4, SMC Pentax FA 1.8 31mm AL Limited, 43mm f1.9 Limited, 77mm f1.8 Limited, Sigma 17-50 f2.8, SMC Pentax DA* 50-135 f2.8, MX + SMC M 50mm f1.4, SMC A 50mm f1.4, SMC A 50mm f1.2, Spotmatic F 55mm f1.8, ES with 55mm f1.8 and 28mm f3.5, Program Plus (Chrome) with SMC A 50mm f1.7, Pentax 6x7, Leica ii, plus misc. odds and sods)

cabstar

Link Posted 30/04/2014 - 19:43
I've had a number of lenses and bodies repaired over the years and all have come back as good as new, bodies have had mirrors, sensors and focus screens cleaned lenses have all been cleaned out and recalibrated for prices not much more than a service.

DSLRs and lenses are so complicated now I don't think will it break more when..
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Concert photography

Currently on a Pentax hiatus until an FF Pentax is released

deck_chair_dave

Link Posted 12/05/2020 - 21:40
I was in a situation similar to the opening post Id bought a second hand DA* 50-135 that was about six days out of its manu warranty and the autofocus died completely. I expressed my disappointment to Pentax Cust Servs and they kindly paid for the repair. The lens was great for about six months, then the same problem of erratic autofocus began to recur sometimes it would work, sometimes it would not.

I was going to send it to Photopia for another service but then, recently, during the covid thing, with a bit of spare time at home, I decided to try and figure out what the conditions had to be for it to work.

I just used it over and over, sometimes in manual sometimes in auto, until it began to work. And then it would stop working and Id repeat the process.

Eventually, I think just because I was using it often, it became more reliable and now it seems to work perfectly all the time. And so now, at least twice a day I point the lens at some plain sky and force it to hunt to its limit in both directions, then focus on a range of different objects around the place at different distances.

I seems like just using it regularly keeps it loosened up and ready to go !

Thought Id mention this here so if anyone gets the problem of erratic autofocus, they can try just using the lens more often see if that simple solution fixes the problem, before paying for a service!

Cheers
Deck Chair Dave

ilovesaabs

Link Posted 13/05/2020 - 20:44
Holy thread resurrection Batman!

Sods law dictates items pack up just outside warranty... Both of my zooms developed problems.... the prime has not given up yet.

Seems the DA 17-70 lens has disappeared into distant memory. I was looking to buy one when my 16-50 was being repaired for the first or second time... tried it in the shop and it wouldn't focus. saved myself nearly 400 that day.
AKA Welshwizard/PWynneJ
Assorted Pentax/Nikon/Mamiya stuff

Crossed-up

Link Posted 06/06/2020 - 22:53
Keeping a resurrected thread going....

I bought a 50-135 with a disclosed lazy SDM from a fellow member here and it soldiered on for many years before finally refusing to wake up at all. Prior to that, like many others experienced it would take a minute or two to gradually come to life, then give a few small movements before gradually increasing to full focus travel.

As it is one of my favourite lenses I acquired another one and put the dead one aside with the intention of sending it off to John Pye for the quoted 180 repair. But I never got around to it.

Despite years of reading all the online discussions on SDM failures, and various theories about dried up grease, failed capacitors needing to charge, faulty batches of motors, and lack of use, Ive never found anything conclusive in terms of the actual failure mode of the motor, which are actually quite simple in terms of construction. Today, I was bored so decided to have a look at the motor in my failed lens.

I stripped it down with the intention of trying to determine if it was a mechanical or electronic problem. The SDM was definitely not seized or sticky, but before, disassembling the motor itself I figured Id tweak the Loctited screw that holds it together (as have others) and it moved the top part of the body around. Out of curiosity I reassembled the lens sufficiently to fit it back on a body to test it whilst still seeing the focus mechanism. For whatever reason I found the SDM sprang immediately to life when I pressed the AF button and it zipped the focus from end to end! I think others have had this experience too over on the US forum. Interestingly the familiar SDM squeaky whistling sound had disappeared too. My theory is that problem relates to the necessary micro-friction properties between the stator and rotor reduce over time to the point that drive is lost, and tweaking the screw changes/restores this to some extent. Without fully disassembling the SDM I cant tell exactly whats going on. But seeing as I now have another working 50-135, Ill wait until I find a cheap failed SDM lens to do that on.

A few pics:








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Gripped K3's|DA10-17|DA*16-50|DA*50-135|DA*200|DA*300|Sigma 150-500

JohnX

Link Posted 07/06/2020 - 08:35
Any chance you could highlight which screw you're referring to please?
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