[pistolero45]

Has anybody developed some type of rear lens cap idea that would have a capacity to charge and keep charged the DA* 50-135mm SDM or the DA*16-50mm 2.8 SDM that are noted for going dead in storage? I was just thinking maybe we could come up with something that had a long-lasting cell in it that would keep a charge on the contacts and therefore the motor would not have to be constantly prodded into working when we put it on our cameras and want to use them. Probably something we could charge through USB port 5-volt or such?

[automorphism]

If you have an extra Pentax camera that can be AC powered maybe you could rig a timer to the camera attached to the lens, and keep the camera in the ON position. Don't know if just turning the camera on will charge the lens though. Never heard of such a strange phenomenon.

[KiloHotelphoto]

Something like the Sigma lens dock might work, maybe.

[pistolero45]

Something like the Sigma lens dock might work, maybe.

Funny you should mention that because that's what I was thinking too. I've never seen one of those in person.

[zapp]

Ask Pentax, they invented the problem.

[clackers]

The reason for aperture block failure isn't whether there's charge on lens contacts or not!

[PJ1]

The reason for aperture block failure isn't whether there's charge on lens contacts or not

Not aperture block. The idea is to stop the SDM motor from going to sleep. I suppose it could work by giving it a nudge periodically.

[RobA_Oz]

I’m not sure what’s meant by keeping a charge on the SDM drive motor. It’s a piezo-electric motor, so just providing a voltage isn’t going to do anything, except maybe cause it to jam. You’d need to simulate an out-of-focus signal to the control board. Having manually freed up my DA*16-50 SDM drive upteen times, I know that a (relatively) considerable torque is needed to unjam it, so it would need more than an occasional pulse to ensure it didn’t get to that condition.

[RobA_Oz]

what??? this is the first time I've heard of this problem - at least in this context. I've had one that stopped working, and sent it back to precision for fixing, but it hadn't been in storage. Is there more than one SDM motor problem? Can someone explain what, exactly, is going on with this, or supply links to threads with descriptions?

There’s only one problem with the old SDM drives, but a lot of confusion about what it actually was (the piezo drive motor used to jam, causing the AF to stop working). There are many threads about the problem and a couple of realistic threads about how to fix it, including reprogramming the drive to disable the SDM and rely on the in-body AF drive (which I did, eventually). The problem was mainly but not exclusively confined to the DA*16-50, although others such as the DA*50-135 also sometimes exhibited it. Early drive replacements sometimes didn’t fix the problem permanently, but later ones appear to have done. Lenses did not need to be “in storage” (Ie put away for weeks or months at a time) for the problem to appear – mine would exhibit it again after a period of a couple of hours of not shooting.

Hoya, then Ricoh, both refused to acknowledge that there was a design issue with the drive, but subsequent replacements seem to have been fitted with drive motors that don’t jam.

[stevebrot]

Idea for keeping a constant charge to sdm motors when in storage

FWIW, having the lens mounted does not provide voltage to the lens unless the camera is turned on and even then, I don't know that doing so would address the SDM issue the same as actually exercising the AF motor. Probably the best solution would be to reprogram the lens to use the drive pawl on the body.


Steve

[pistolero45]

Thanks Steve I think I may do that.
Now if I can only figure out how to get my even more favorite lens, the da* 60-250 fixed. It is having its own focus motor problems but I can live with that. Now it's permanently stopped down to F16 uggh🥺

---------- Post added 06-10-20 at 01:01 PM ----------

The reason for aperture block failure isn't whether there's charge on lens contacts or not!

I wasn't referencing the aperture block problem. Just the cranky SDM motor that fails to power up until you push and push and push the AF button odd nauseam.

---------- Post added 06-10-20 at 01:03 PM ----------

I’m not sure what’s meant by keeping a charge on the SDM drive motor. It’s a piezo-electric motor, so just providing a voltage isn’t going to do anything, except maybe cause it to jam. You’d need to simulate an out-of-focus signal to the control board. Having manually freed up my DA*16-50 SDM drive upteen times, I know that a (relatively) considerable torque is needed to unjam it, so it would need more than an occasional pulse to ensure it didn’t get to that condition.

Thanks for the info. I had always heard that it was a failure of a capacitor to hold charge, therefore I thought keeping a charge on it would remedy the problem.

[UncleVanya]

I started to respond yesterday... But every draft seemed snarky. Here's my OPINION, I can't prove it. But it fits known facts.

Capacitor/electrical theory is nonsense. Lenses that are new can sit in a box for years and never have sdm issues out of the box that I have heard of.

One fix rarely used is to rapidly focus the lens back and forth for a few minutes. This supposedly reduces friction in the focus mechanisms. This in theory allows the sdm to overcome the static friction.

[rogerstg]

One fix rarely used is to rapidly focus the lens back and forth for a few minutes. This supposedly reduces friction in the focus mechanisms.

I've often wondered if the SDM issue was less a problem with faulty motors and more an issue with lens build. A lens built with tighter than normal tolerances might stress the motor too much for long SDM life. It would help explain why some models seem to have fewer failures, repeated repairs fail with some lenses, "exercising" the lens sometimes helps, some lenses focus slowly, etc.

FWIW, I have two SDM lenses; DA* 50-135 and DA* 16-50. The 16-50 is from 2007 and the 50-135 from 2008. (Knocking on wood) SDM has been fast, quiet and reliable. (still knocking )

[RobA_Oz]

I've often wondered if the SDM issue was less a problem with faulty motors and more an issue with lens build. A lens built with tighter than normal tolerances might stress the motor too much for long SDM life. It would help explain why some models seem to have fewer failures, repeated repairs fail with some lenses, "exercising" the lens sometimes helps, some lenses focus slowly, etc.

FWIW, I have two SDM lenses; DA* 50-135 and DA* 16-50. The 16-50 is from 2007 and the 50-135 from 2008. (Knocking on wood) SDM has been fast, quiet and reliable. (still knocking )

I think it’s more to do with inadequate motors, rather than faulty ones. Faulty electrical devices tend to fail early in their lives, whereas the early SDM motors failed after (comparatively) long periods. The repeated repairs were probably due to replacement with the same type of motor, but it’s not likely we’ll ever know for sure.

[pistolero45]

I started to respond yesterday... But every draft seemed snarky. Here's my OPINION, I can't prove it. But it fits known facts.

Capacitor/electrical theory is nonsense. Lenses that are new can sit in a box for years and never have sdm issues out of the box that I have heard of.

One fix rarely used is to rapidly focus the lens back and forth for a few minutes. This supposedly reduces friction in the focus mechanisms. This in theory allows the sdm to overcome the static friction.

I sold cameras and lenses not just Pentax but mostly Pentax for over 20 years. Trust me they do occasionally come dead out of box new. I personally bought two back-to-back DA* 50 - 135 2.8 SDM motor lenses. The first one was squeaking with a failing SDM motor right out of the box. The second one failed within three months. They fixed it and it failed with another year. And I've had similar issues on my DA*60-250mm. Sometimes it just will not autofocus no matter how often I push the button down so I flip it to manual and now it's decided to lock itself at F-16 and become a paperweight.