Da*16-50 2.8 sdm

**photogem** · 04-05-2022, 09:31 PM

Originally posted by UncleVanya

I also do not subscribe to the belief that idle non-use is the culprit as many lenses that sit for years seem unaffected.
I do know that it would stick in our minds and could seem that way to most users. My lenses get bursts of use and then sit idle for a long time as I have too many lenses to keep them all happy.

Many had the opposite experience. In the German Pentaxiansforum there is a nice tutorial how to bring such a stuck SDM motor back to working again, if it isn't stuck too strong:
https://www.pentaxians.de/40456504nx51499/tipps-und-tricks-f41/tutorial-sdm-...da-t18366.html

Many had some success heating that part were the motor sits up with a hairdryer.
This is the most common method because most would not dare to open the lens.

Not how I would do it, I also don't like using a hairdryer or similar to losen the protective glass of the LCD-screen, a method many apply.
I feel the heat can damage other parts as well.

pentasonic49 · 04-10-2022, 07:22 AM - **1 Like**

My copy of this lens is one of the first made and the SDM failed after about 2 years. I followed the video instructions on this forum and dismantled the rear of the lens and used a small JIS crosspoint screwdriver to exercise the SDM motor, it will turn backwards add forwards and then a stop is felt. The screw did not loosen during this proceedure. This fix lasted a few months before the old problem was back. My fix was to dismantle the lens again and drill a hole in the backplate in line with the screw, so I could exercise the motor without dismantling the lens again. The hole is inboard of the sealing ring so water resistance is not compromised. The SDM still works after about 14 years, sometimes requiring use of the screwdriver which is kept in the camera bag. I don't use the lens much, if it was in frequent use the SDM might never have failed.
Having a quick look at the German tutorial reminded me that I managed to loose one of the tiny gold springs while dismantling the lens the second time, not down inside the lens, fortunately. I decided to sacrifice an unloved 28-90 and the parts were identical, I still have the spare springs and pins in a film canister.

**photogem** · 04-10-2022, 10:40 AM

Originally posted by pentasonic49

... My fix was to dismantle the lens again and drill a hole in the backplate in line with the screw, so I could exercise the motor without dismantling the lens again. The hole is inboard of the sealing ring so water resistance is not compromised. The SDM still works after about 14 years, sometimes requiring use of the screwdriver which is kept in the camera bag. I don't use the lens much, if it was in frequent use the SDM might never have failed.

That is partly why I love this forum: Gems shared. Of course not for those who want to sell the lens later on
but it shows how obvious an idea could be but just doesn't pop up. Great!

Originally posted by pentasonic49

Having a quick look at the German tutorial reminded me that I managed to loose one of the tiny gold springs while dismantling the lens the second time, not down inside the lens, fortunately. I decided to sacrifice an unloved 28-90 and the parts were identical, I still have the spare springs and pins in a film canister.

I place some strong tape on the outside over the contacts, which I cut out so it fits perfectly. That has worked in most cases.
Sometimes I tried to repair lenses but they were beyond repair, so I kept parts like those springs and contacts.

04-10-2022, 07:22 AM - 1 Like	#17
pentasonic49 Veteran Member Join Date: Oct 2012 Location: weston-super-mare Posts: 395	My copy of this lens is one of the first made and the SDM failed after about 2 years. I followed the video instructions on this forum and dismantled the rear of the lens and used a small JIS crosspoint screwdriver to exercise the SDM motor, it will turn backwards add forwards and then a stop is felt. The screw did not loosen during this proceedure. This fix lasted a few months before the old problem was back. My fix was to dismantle the lens again and drill a hole in the backplate in line with the screw, so I could exercise the motor without dismantling the lens again. The hole is inboard of the sealing ring so water resistance is not compromised. The SDM still works after about 14 years, sometimes requiring use of the screwdriver which is kept in the camera bag. I don't use the lens much, if it was in frequent use the SDM might never have failed. Having a quick look at the German tutorial reminded me that I managed to loose one of the tiny gold springs while dismantling the lens the second time, not down inside the lens, fortunately. I decided to sacrifice an unloved 28-90 and the parts were identical, I still have the spare springs and pins in a film canister. Last edited by pentasonic49; 04-10-2022 at 07:28 AM.

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04-05-2022, 09:31 PM	#16
photogem Site Supporter Join Date: Apr 2015 Posts: 3,522	Originally posted by UncleVanya I also do not subscribe to the belief that idle non-use is the culprit as many lenses that sit for years seem unaffected. I do know that it would stick in our minds and could seem that way to most users. My lenses get bursts of use and then sit idle for a long time as I have too many lenses to keep them all happy. Many had the opposite experience. In the German Pentaxiansforum there is a nice tutorial how to bring such a stuck SDM motor back to working again, if it isn't stuck too strong: https://www.pentaxians.de/40456504nx51499/tipps-und-tricks-f41/tutorial-sdm-...da-t18366.html Many had some success heating that part were the motor sits up with a hairdryer. This is the most common method because most would not dare to open the lens. Not how I would do it, I also don't like using a hairdryer or similar to losen the protective glass of the LCD-screen, a method many apply. I feel the heat can damage other parts as well.

04-10-2022, 10:40 AM	#18
photogem Site Supporter Join Date: Apr 2015 Posts: 3,522	Originally posted by pentasonic49 ... My fix was to dismantle the lens again and drill a hole in the backplate in line with the screw, so I could exercise the motor without dismantling the lens again. The hole is inboard of the sealing ring so water resistance is not compromised. The SDM still works after about 14 years, sometimes requiring use of the screwdriver which is kept in the camera bag. I don't use the lens much, if it was in frequent use the SDM might never have failed. That is partly why I love this forum: Gems shared. Of course not for those who want to sell the lens later on but it shows how obvious an idea could be but just doesn't pop up. Great! Originally posted by pentasonic49 Having a quick look at the German tutorial reminded me that I managed to loose one of the tiny gold springs while dismantling the lens the second time, not down inside the lens, fortunately. I decided to sacrifice an unloved 28-90 and the parts were identical, I still have the spare springs and pins in a film canister. I place some strong tape on the outside over the contacts, which I cut out so it fits perfectly. That has worked in most cases. Sometimes I tried to repair lenses but they were beyond repair, so I kept parts like those springs and contacts.