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02-12-2019, 01:55 AM   #1
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DA* 55 1.4 SDM Problem

Hello
I need some advice. I purchased a almost new Pentax DA 55* SDM. The previous owner has switched to other company.


When the lens came the SDM motor first did not work. It started to work after many tries and now works well.

Is this some sign of future problems?

The DA55* is from 2015 and has a serialnumber starting with 9131

Can I find out what is the manufacture date?

Price was good and the owner is fine to take it back. He gave me 2 weeks to check and make decision

Thank you.


02-12-2019, 03:05 AM   #2
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sdm system has capacitors, that said they tend to fall "asleep" after long times on no use, so try to use it at least a couple of times per week and it should be fine. if you let it rest for long times that sleep becomes death for the motor.
02-12-2019, 06:23 AM - 4 Likes   #3
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QuoteOriginally posted by shyrsio Quote
sdm system has capacitors, that said they tend to fall "asleep" after long times on no use, so try to use it at least a couple of times per week and it should be fine. if you let it rest for long times that sleep becomes death for the motor.
Oh, no, not this again. One idiotic Youtube video, and people would so readily believe it...
There's no such capacitor - one that requires minutes of charging (not the tiny ones you barely see on control board). There can't be any such capacitor. Piezo motors don't require such capacitors, they're not *((*@&# flashes! If they did require it, they would work like flashes, i.e. one AF movement and then 1-3 seconds pause until the capacitor recharges.
Besides, this theory means that every SDM lens would be dead on arrival because they're not constantly powered on all the way from the factory to your home.
Disassemble the lens, try to find such a capacitor, and if you do find it I will buy your lens at a new-in-box price, and eat it.
02-12-2019, 06:50 AM   #4
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QuoteOriginally posted by Kunzite Quote
Oh, no, not this again. One idiotic Youtube video, and people would so readily believe it...
There's no such capacitor - one that requires minutes of charging (not the tiny ones you barely see on control board). There can't be any such capacitor. Piezo motors don't require such capacitors, they're not *((*@&# flashes! If they did require it, they would work like flashes, i.e. one AF movement and then 1-3 seconds pause until the capacitor recharges.
Besides, this theory means that every SDM lens would be dead on arrival because they're not constantly powered on all the way from the factory to your home.
Disassemble the lens, try to find such a capacitor, and if you do find it I will buy your lens at a new-in-box price, and eat it.
Correct, but not a particularly polite way of saying so.

02-12-2019, 06:53 AM   #5
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QuoteOriginally posted by gatorguy Quote
Correct, but not a particularly polite way of saying so.
Sorry about that, I'm not in the mood to be polite towards a third party filling the Internet with nonsense.

I mean no disrespect for shyrsio - he just implicitly trusted that Youtube guy. It's the "Internet expert". To be clear.
02-12-2019, 07:00 AM - 2 Likes   #6
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QuoteOriginally posted by Kunzite Quote
Oh, no, not this again. One idiotic Youtube video, and people would so readily believe it...
There's no such capacitor - one that requires minutes of charging (not the tiny ones you barely see on control board). There can't be any such capacitor. Piezo motors don't require such capacitors, they're not *((*@&# flashes! If they did require it, they would work like flashes, i.e. one AF movement and then 1-3 seconds pause until the capacitor recharges.
Besides, this theory means that every SDM lens would be dead on arrival because they're not constantly powered on all the way from the factory to your home.
Disassemble the lens, try to find such a capacitor, and if you do find it I will buy your lens at a new-in-box price, and eat it.
T H I S ! ! ! ^^^^^

What else might be the cause? I'm not sure but capacitors aren't a rational answer. Perhaps stiction? Stiction - Wikipedia

Are we ever sure these are piezo? This source from 2015 discusses the design of ultrasonic motors. In it they reference the smallest developed motors of this type and they all look too big for our sdm modules.

Micro Motor - an overview | ScienceDirect Topics
02-12-2019, 07:05 AM   #7
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Stiction is the typical cause of such issues, for piezo motors.
I'm quite sure all SDM are piezo motors.

02-12-2019, 09:30 AM   #8
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QuoteOriginally posted by solatana Quote
Is this some sign of future problems?
Many SDM lenses have this problem. The only certainty is, it won't get any better.

I bought a DA*55 used with an unknown history. It has always behaved like that. After a minute or two of attempts to wake up, it focuses. It'll keep working fine after that if I keep using it. The focus action is quiet and somewhat slow, but precise.

I just checked mine to see if it still works. While I was getting it to wake up, I looked in Lightroom to see the last photo taken with it. It was 8 months ago. So I don't always follow the commonly accepted advice to use it often.

No one can say for sure if your lens will fail. The DA*55 risk is greater because there is no backup screw drive, so it could be a manual focus lens at some point. Optically, I like the lens. I'd probably fix it myself if it broke today.
02-12-2019, 09:45 AM   #9
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More ironically, with all the reports on SDM issue, Pentax continues to make these SDM DA lenses as if SDM issues don't exist. What they do is beyond my imagination.
02-12-2019, 11:47 AM   #10
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My 60-250 issue

QuoteOriginally posted by solatana Quote
Hello
I need some advice. I purchased a almost new Pentax DA 55* SDM. The previous owner has switched to other company.


When the lens came the SDM motor first did not work. It started to work after many tries and now works well.

Is this some sign of future problems?

The DA55* is from 2015 and has a serialnumber starting with 9131

Can I find out what is the manufacture date?

Price was good and the owner is fine to take it back. He gave me 2 weeks to check and make decision

Thank you.
QuoteOriginally posted by shyrsio Quote
sdm system has capacitors, that said they tend to fall "asleep" after long times on no use, so try to use it at least a couple of times per week and it should be fine. if you let it rest for long times that sleep becomes death for the motor.
QuoteOriginally posted by gatorguy Quote
Correct, but not a particularly polite way of saying so.
QuoteOriginally posted by Kunzite Quote
Sorry about that, I'm not in the mood to be polite towards a third party filling the Internet with nonsense.

I mean no disrespect for shyrsio - he just implicitly trusted that Youtube guy. It's the "Internet expert". To be clear.
QuoteOriginally posted by UncleVanya Quote
T H I S ! ! ! ^^^^^

What else might be the cause? I'm not sure but capacitors aren't a rational answer. Perhaps stiction? Stiction - Wikipedia

Are we ever sure these are piezo? This source from 2015 discusses the design of ultrasonic motors. In it they reference the smallest developed motors of this type and they all look too big for our sdm modules.

Micro Motor - an overview | ScienceDirect Topics
QuoteOriginally posted by Kunzite Quote
Stiction is the typical cause of such issues, for piezo motors.
I'm quite sure all SDM are piezo motors.
QuoteOriginally posted by Just1MoreDave Quote
Many SDM lenses have this problem. The only certainty is, it won't get any better.

I bought a DA*55 used with an unknown history. It has always behaved like that. After a minute or two of attempts to wake up, it focuses. It'll keep working fine after that if I keep using it. The focus action is quiet and somewhat slow, but precise.

I just checked mine to see if it still works. While I was getting it to wake up, I looked in Lightroom to see the last photo taken with it. It was 8 months ago. So I don't always follow the commonly accepted advice to use it often.

No one can say for sure if your lens will fail. The DA*55 risk is greater because there is no backup screw drive, so it could be a manual focus lens at some point. Optically, I like the lens. I'd probably fix it myself if it broke today.
QuoteOriginally posted by hyyz Quote
More ironically, with all the reports on SDM issue, Pentax continues to make these SDM DA lenses as if SDM issues don't exist. What they do is beyond my imagination.
My 60-250 failed as soon as I got it home. Sent it in fr warranty repairs. Got it back, worked great, optically superb, but it is not a focal length I use very much, so it has long periods of dormancy.. Picked it up one day, would nt work, kept pushing and pushing the autofocus button, finally swung back to life, and it works fine all day after that. A few days in the box and it's dead again; the longer you leave it, the more it takes to come back to life. I thought it was capacitors as well. I've been living with this problem ever since, and just remembering to prime the lens every time. Anyway, a couple of weeks ago it started >>>SQUEAKING<<< on focussing, which finally prompted me to take it back AGAIN. Two week back east in Pentax Canada (I'm assuming Toronto somewhere), they can't fix it, and now the lens has been sent back to Pentax Japan for it's second overhaul.

I sure hope they get this thing working. To be honest, I was thinking of selling it, not because of this issue, but because I use it so rarely. I'm more of a Limited/prime kind of guy. And that thing's so big, heavy, obtrusive and intimidating, I rarely take it travelling.

Yeah, SDM sucks, it's time to abandon it.

So it's stiction, you think? My 16-85 works great, always, so that's not a piezo motor?

Cheers,
Cameron
02-12-2019, 12:15 PM   #11
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Cameron, stiction is a known issue with piezo motors. You should take this as a fact.
The 16-85 has a DC motor, by the way - which is more reliable than the micromotor. You would be happy to know that Pentax indeed abandoned the SDM micromotors, as in launching new lenses with other types of motors (including piezo), since 2009.

There can't be any kind of capacitor for the reasons stated:
- no such large capacitor being present in a lens
- piezo motors not needing them (they're quite generic
- if piezo motors would need such a large capacitor, they would work like flashes i.e. the AF motor would move once, then have to wait for a capacitor recharge, then again. We're having continuous AF though so...
- if piezo motors would need such a large capacitor, all SDM (USM, AF-S...) lenses would arrive DoA because there's no way to keep the capacitor filled until delivery. Not just your one 60-250 sample.
Don't believe whatever some incompetent spewed in a Youtube video!

SDM is fine. The first type of SDM micromotor used in the 16-50 and 50-135 wasn't, nor the idea of using micromotors in * lenses - micromotors are entry-level technology. I strongly suspect that current SDM micromotors don't fail more often than Canon's, Nikon's etc.
Ring-type SDM is excellent. Well, if that motor "needs" a large capacitor, it must be filling all the space inside the barrel - effectively not leaving any room for optical glass.

Here's the ring-type SDM next to its micromotor sibling:
http://www.ricoh-imaging.co.jp/japan/products/star_lens/special/sp_dfa50-14/img/a6_img_01.jpg
02-12-2019, 12:17 PM   #12
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QuoteOriginally posted by Cambo Quote
So it's stiction, you think? My 16-85 works great, always, so that's not a piezo motor?

Cheers,
Cameron
That's just a guess. Stiction gets worse as things sit.

The 16-85 is a DC motor, and my guess is the 16-85 motor has better torque than the sdm motors used in past devices.
02-12-2019, 04:38 PM   #13
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QuoteOriginally posted by Kunzite Quote
Oh, no, not this again. One idiotic Youtube video, and people would so readily believe it...
There's no such capacitor - one that requires minutes of charging (not the tiny ones you barely see on control board). There can't be any such capacitor. Piezo motors don't require such capacitors, they're not *((*@&# flashes! If they did require it, they would work like flashes, i.e. one AF movement and then 1-3 seconds pause until the capacitor recharges.
Besides, this theory means that every SDM lens would be dead on arrival because they're not constantly powered on all the way from the factory to your home.
Disassemble the lens, try to find such a capacitor, and if you do find it I will buy your lens at a new-in-box price, and eat it.
I dont really know about any capacitors, I guess I must have read/heard it somewhere. What I can tell you is this: I have a 17-70/4 SDM and it behaves like that. when i pick the camera after some days, its pretty lazy. after a couple cycles of focusing around its back to speed.
02-12-2019, 04:44 PM   #14
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QuoteOriginally posted by shyrsio Quote
I dont really know about any capacitors, I guess I must have read/heard it somewhere. What I can tell you is this: I have a 17-70/4 SDM and it behaves like that. when i pick the camera after some days, its pretty lazy. after a couple cycles of focusing around its back to speed.
I don't know where you have heard about it, but the source is some dude's Youtube video.
Stiction is a reasonable explanation. A capacitor needing minutes to recharge (and then doing nobody knows what) isn't.
02-12-2019, 04:48 PM   #15
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Capacitors of the sizes in these lenses would charge faster than human perception could register.
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