Is this the reason why SDM lenses need to be used often and are prone to fail?


davidstorm

Link Posted 01/08/2016 - 16:59
I was reading a forum post the other day about the unreliability of he SDM lenses, e.g. DA*50-135 and DA*16-50. One of the things most often said about these lenses is that they 'need to be used often' and if they haven't been used for a long period of time they won't 'wake up'.

Now, I used to take this with a pinch of salt, not having any decent logic to understand it, but recently I experienced this with my 50-135. I had not used it for approx. 6 months, then mounted it on my K-3 and tried to autofocus. Guess what? Nothing happened. I left it a short while (still on the camera), twisted the focus ring a few times and tried again. Guess what? It focussed. Since then, it appears OK, although I haven't used it much.

What can explain this? Has anyone heard about the capacitor that is apparently in the lens electronics? A capacitor, like a battery, stores electricity. It is prone to leaking that electricity over a period of time, i.e. discharging. If the SDM motor relies on smooth power delivery from the capacitor in order to make it focus, could this explain why an SDM lens won't immediately wake up if it hasn't been used for a while? Could this be why it worked when the lens had been on the camera a few minutes, because the capacitor was by then fully charged?

I don't know the answer, but it begs another question in my mind. Many of us (not me just yet) have had SDM motors replaced. Could it be that the motor was not / is not the issue? Could it be capacitors causing the problems? I know from experience with other electrical equipment that some capacitors can be prone to failure in some circuits.

This is pure conjecture, but I would be interested to know what others think, especially if there's anyone on here who understands the circuit design on the SDM lenses.

I'm sure you all won't be shy in giving your thoughts on this!

Regards
David
My Website http://imagesbydavidstorm.foliopic.com

Flickr

Some cameras, some lenses, some bits 'n' bobs

Daronl

Link Posted 01/08/2016 - 18:49
Very interesting post David and I just sold a very tempramental DA* 50-135, (2nd one I gave up on) and had 4 other SDM's changed by ASAHI Optic (On 4 other DA* lenses).

Two of them never ever failed or played up, one of which was the DA* 16-50, reputed to be the most unreliable, the other was 200mm.

I changed the SDM's as a precaution in case I sold them in the near future.

The other two lenses having new SDM motors was 60-250; at best tempremental at worst just wouldn't wake up some times; the 300mm would usually wake up if I turned the small screw drive "dog" on the base of the lens with a small screwdriver.

However since ASAHI OPTIC changed the originals for the latest SDM's not only are they 100% reliable, no matter how long they are in the drawer, but they seem to be " crisper" and faster focussing.

However the latter point regarding focus speed has not been measured.

Going back to your point David, the questions for Ricoh ( or Johnsons Photopia) might be;

1. Would the capacitor be changed when an SDM is changed
2. If not and the capacitors are the real culprits then the newly fitted SDM's will be
affected sporadically
3. Are the latest capacitors uprated from the originals.

The only thing I am sure about is that the failures were random in frequency and " stubborness" ( if you know what I mean).

I have been using the HD 150-450 for birds over the last year which is an absolute rock, but last week I took the 300 and 200 out and it is obvious they are quicker focussing in comparison.

By the way ASAHI OPTICS are not far of "half the cost" on replacment of SDM's compared to other, and they are very knowlegeable so I will see what their view is regarding the capacitor discussion, it is a very interesting point though.

Regards
Daronl

davidstorm

Link Posted 01/08/2016 - 19:16
Thanks for your input Daronl, does anyone else have any thoughts on this? One reason for asking is my 50-135 has the 'latest' motor fitted, but I've still experienced this behaviour.

Has anyone ever questioned what gets replaced when a SDM Motor is fixed?

Regards
David
My Website http://imagesbydavidstorm.foliopic.com

Flickr

Some cameras, some lenses, some bits 'n' bobs
Last Edited by davidstorm on 01/08/2016 - 19:16

McBrian

Link Posted 01/08/2016 - 20:40
My DA*16-50 caused me a bit of embarrassment recently as I sent it to SRS as part of a trade in only for it not to work when it got to Watford

It's had a replacement SDM and circuit board at JPS, I never had any problems with it and it did (still does) work on return from SRS

It's been sitting on the shelf here since I got the K1back in April, I've have just put it on my K3ii and it was dead but a quick change in to LV and a few seconds press of the back focus button brings it back to life, didn't need to twist anything, I think this scenario supports the capacitor theory although I have no idea if that is true or false.
Cheers
Brian.
LBA is good for you, a Lens a day helps you work, rest and play.

Gwyn

Link Posted 01/08/2016 - 21:08
Touching wood, and I may regret posting this but I have had no problems with any of my SDM lenses, and they can go unused for over a year the way things are with me at the moment.
The 17-70 lay untouched for nearly two years, but fired up first go, same with the 50-135. The 60-250 has been used more often but even then it goes for many many months without use. I used it last year in September and only picked it up again this year in June, no problem at all.

VividArt

Link Posted 02/08/2016 - 08:25
Good topic David.
I have read as much as I could dig up on the subject, I too own the 50-135 and worry..

I had an unexpected shutter click the other day on my K52s. I had just mounted the lens, was half pressing and the mirror flapped as if it was taking a shot..
No shot was taken by the camera.
I pull mine off the shelf every few months and keep using it as has been suggested. My dry fired shot was the only incident that day, I was chasing airplanes at full zoom and it worked fine for the few hundred shots I took that day.
Related? Likely not, but could have been that the lens was not firmly attached. It was, but I re clicked it into place after the failed shot just to be sure and all was well for the rest of the day..

A note on the causes I've read, likely you have seen these as well but it's worth mentioning.
I read that they used a type of grease in the lens that gets dried up, causes the motor to "load" unnecessarily against the resistance the dried grease offers, this strain on the motor will ask more of the capacitor(s) and will attempt to overcome the resistance eventually leading to the actual motor failing.

The capacitor thing is another can of worms that not many people have heard of.

The story goes: A design for a series of efficient capacitors was "stolen" by a foreign country that has since taken over the market in electronics. You know who...
What I have heard in the electronics industry is that the formula was stolen but was incomplete..
Millions of capacitors were made with this botched formula, they were then used in all electronics across the planet including Japan.
Every kind of device got them for a period of almost 20 yrs, they are poorly made and they often burst. I have changed many of these myself, the types of devices I've seen them in have been top shelf Japanese made pc mother boards, all audio equipment made by Korg, Tascam, Lexicon, Motu, the list goes on and on.
There are thousand of threads out there on the stupid capacitors, they made it into everything. I wouldn't be surprised if they were used to save money on the lenses..

A capacitor should bleed itself within 24 hrs usually, but the instant the camera is turned on, the lens is also fired up electronically - this should recharge a good capacitor at the speed of light.
The new capacitors made with graphine, that replace batteries keep their charge for a very long time.
But when the lens pause's as your lens did, I would imagine that the capacitor has begun to leak it's electrolyte and it's capacity has become diminished causing a vague connection to the rest of the electronics including the motor controller or the other mythical grease issue.
In some cases allowing the equipment to warm up will recharge a dying capacitor but it will effect the performance of the lens or device. I have to replace 12 big ones in a Tascam DM-24 digital mixer that needs a half hour to warm up, the first half hour sounds like static or fried speakers. After the warm up it's very usable but those capacitors are bulging and waiting to burst, I don't use the mixer at this point in time...

On a positive note, the lens can be converted to screw drive by hacking the firmware, I read that doing so before the motor dies is best, other wise the lens might need to be taken apart to free up the sticky motor first..I hear they track faster than SDM..
Then they said they switched to a new motor...? Who knows. The capicitor thing I have seen personally many times and know that they were used extensively..Pentax is pretty hush hush about what they actually fix when something goes bad, likely they didn't know about the capacitors until well after the lenses were designed and sold. Not really the sort of thing anybody would want to admit to..

It's an upsetting topic, I love the lens, can't imagine not having it in my kit. I bought mine almost three years ago, even making sure I bought one that was not in the flagged serial number list, the extended warranty I bought gets me another two years. Here's to hoping right along with my camera bodies and whatever else I own that has them in it.. :-/

Good luck with yours. I hope the info was somewhat helpful.

Regards,


Damien
Last Edited by VividArt on 02/08/2016 - 08:36

VividArt

Link Posted 02/08/2016 - 12:37
VividArt wrote:
Good topic David.
I have read as much as I could dig up on the subject, I too own the 50-135 and worry..

I had an unexpected shutter click the other day on my K52s. I had just mounted the lens, was half pressing and the mirror flapped as if it was taking a shot..
No shot was taken by the camera.
I pull mine off the shelf every few months and keep using it as has been suggested. My dry fired shot was the only incident that day, I was chasing airplanes at full zoom and it worked fine for the few hundred shots I took that day.
Related? Likely not, but could have been that the lens was not firmly attached. It was, but I re clicked it into place after the failed shot just to be sure and all was well for the rest of the day..

A note on the causes I've read, likely you have seen these as well but it's worth mentioning.
I read that they used a type of grease in the lens that gets dried up, causes the motor to "load" unnecessarily against the resistance the dried grease offers, this strain on the motor will ask more of the capacitor(s) and will attempt to overcome the resistance eventually leading to the actual motor failing. Temperature can be a factor in storing the lens, I would imagine if the lens were stored in a cool place it might make the grease act differently than stored in a warm place. We also need to think about gravity and it's effects on grease over time especially if the lens were stored in a hot place.

The capacitor thing is another can of worms that not many people have heard of.

The story/rumor goes like this:
A design for a series of efficient capacitors was "stolen" by a foreign country that has since taken over the market in electronics. You have a guess who...
Allegedly stolen anyway.
What I have heard in the electronics industry is that the formula was stolen but was incomplete..
Millions of capacitors were made with this botched formula, they were then used in all electronics across the planet including Japan.
Every kind of device got them for a period of almost 20 yrs, they are poorly made and they often burst. I have changed many of these myself, the types of devices I've seen them in top shelf Japanese made pc mother boards, all audio equipment within a certain time frame made by Korg, Tascam, Lexicon, Motu, most manufacturers, the list could go on and on.
There are thousand of threads out there on the stupid capacitors, they made it into everything. I wouldn't be surprised if they were used to save money on the lenses..
Or they were used unknowingly by Pentax.
A capacitor should bleed itself within 24 hrs usually, but the instant the camera is turned on, the lens is also fired up electronically - this should recharge a good capacitor at the speed of light.
The new capacitors made with graphine, that replace batteries keep their charge for a very long time.
But when the lens pause's as your lens did, I would imagine that the capacitor has begun to leak it's electrolyte and it's capacitance has become diminished causing a vague connection to the rest of the electronics including the motor controller or the other mythical grease issue.. Leaking is the worst case of course, they can fail and remain intact..
In some cases allowing the equipment to warm up will recharge a dying capacitor but it will effect the performance of the lens or device. I have to replace 12 big ones in a Tascam DM-24 digital mixer that needs a half hour to warm up, the first half hour sounds like static or fried speakers. After the warm up it's very usable but those capacitors are bulging and waiting to burst, I don't use the mixer at this point in time...

On a positive note, the lens can be converted to screw drive by hacking the firmware, I read that doing so before the motor dies is best, other wise the lens might need to be taken apart to free up the sticky motor first..I hear they track faster than SDM..
Then they said they switched to a new motor...? Who knows. The capacitor thing I have seen personally many times and know that they were used extensively..Pentax is pretty hush hush about what they actually fix when something goes bad, likely they didn't know about the capacitors until well after the lenses were designed and sold. Not really the sort of thing anybody would want to admit to.. with Pentax's commitment to quality then finding out they had inadvertently chosen a bad supplier...it's a bum deal for both parties. It would be nice if Pentax just gave us the adapted firmware. It would be a nice way to make up for the expensive lens failing so soon. It would put a lot of people at ease I think. I feel like each shot it takes might be it's last..
If they had just stayed in Japan!

It's an upsetting topic, I love the lens, can't imagine not having it in my kit. I bought mine almost three years ago, even making sure I bought one that was not in the flagged serial number list, the extended warranty I bought gets me another two years. Here's to hoping right along with my camera bodies and whatever else I own that has them in it.. :-/

Good luck with yours. I hope the info was somewhat helpful.

Regards,


Damien

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