How To: Convert SDM to ScrewDrive + Video

**UncleVanya** · 09-26-2017, 12:09 PM

Originally posted by mattb123

KEH did an initial repair that failed again after a few months. I sent it back to them and they decided they couldn't fix it and refunded that initial repair cost. They said maybe Precision would have more luck but I've been hesitant to put more money into it so instead I put that money toward a Tamron 70-200/2.8 because I needed to cover that range for an upcoming paid shoot.
I'm now just holding on to the 60-250 in hopes that an inexpensive fix or conversion might come along but I'm not holding my breath. I really like the size, handling, and rendering of that lens as well as the peace of mind WR gives.

Well darn. That was my only idea. Even without AF that's a pretty nice lens. But there are less bulky options if AF is not required. So sorry that this lens is orphaned - I have searched for an answer but I haven't found one yet. Ideally if Pentax would just make it an option to switch between SDM and Screwdrive on these lenses using a body configuration based on lens serial id it would solve all the problems for at least newer bodies.

**mattb123** · 09-26-2017, 12:53 PM

Originally posted by UncleVanya

Well darn. That was my only idea. Even without AF that's a pretty nice lens. But there are less bulky options if AF is not required. So sorry that this lens is orphaned - I have searched for an answer but I haven't found one yet. Ideally if Pentax would just make it an option to switch between SDM and Screwdrive on these lenses using a body configuration based on lens serial id it would solve all the problems for at least newer bodies.

I'd be thrilled if I could do that on the K-1. I have other options for that range now so the lens just sits.

yucafrita · 09-28-2017, 11:30 PM

For the 60-250, what would happen if one takes out the SDM contacts from the mount or stick a tape over it? Would this trigger the lens to use the screw-drive and still communicate properly to the camera body via the other contacts?

it's just an idea since I dont have the 60-250 (but considering it).

In a german Pentax forum a user mentions that C0 has to be changed at two positions but he cant remember where he read this. Does this ring a bell?

Duc-Driver · 09-29-2017, 12:49 AM

a guy from russia send me his 60-250 rom with working screwdrive. It was modified at a russian repair center.
But that lensrom has the same mod like we know with changing "C0" to "80" (ok, at this lens it's changed to "00" but that doesn't matter) - so there have to be a (small) hardware hack.
Small because he have not paid that much for that conversation.

If you isolte the sdm contacts and use a modified lensrom, autofocus is working between 1,1m to 2,5m and 5m to 10m.
That is also the range if you only use a modified lensrom with sdm contacts...in this range screwdrive is working but if you go over it - for example 3m - the lens switches to sdm.

With isolatet contacts and if you go for example to 3m, the body gives some error by blinking display - if you go back to 1,1m all is normal again.
So there is some error while focusing over the range from 1,1m to infinity...something is given a wrong data or something like that to the camera.
I tested that with my K20D and my K3 - on both it's the same.

Maybe you have to disconnect the sdm engine or something like that but you have to dissassemble the lens a bit (and mine is still working so far).
I would to that (test that) with a failed 60-250, but not with my good one.

Originally posted by UncleVanya

Ideally if Pentax would just make it an option to switch between SDM and Screwdrive on these lenses using a body configuration based on lens serial id it would solve all the problems for at least newer bodies.

that would be very nice but Pentax will never do this because then they don't get money for a damaged sdm

Last edited by Duc-Driver; 09-29-2017 at 12:55 AM.

**UncleVanya** · 09-29-2017, 06:22 AM

Originally posted by Duc-Driver

a guy from russia send me his 60-250 rom with working screwdrive. It was modified at a russian repair center.
But that lensrom has the same mod like we know with changing "C0" to "80" (ok, at this lens it's changed to "00" but that doesn't matter) - so there have to be a (small) hardware hack.
Small because he have not paid that much for that conversation.

If you isolte the sdm contacts and use a modified lensrom, autofocus is working between 1,1m to 2,5m and 5m to 10m.
That is also the range if you only use a modified lensrom with sdm contacts...in this range screwdrive is working but if you go over it - for example 3m - the lens switches to sdm.

With isolatet contacts and if you go for example to 3m, the body gives some error by blinking display - if you go back to 1,1m all is normal again.
So there is some error while focusing over the range from 1,1m to infinity...something is given a wrong data or something like that to the camera.
I tested that with my K20D and my K3 - on both it's the same.

Maybe you have to disconnect the sdm engine or something like that but you have to dissassemble the lens a bit (and mine is still working so far).
I would to that (test that) with a failed 60-250, but not with my good one.

that would be very nice but Pentax will never do this because then they don't get money for a damaged sdm

I'm lost a bit by this reply. Are you saying the modified lens from Russia works just fine over the entire range?
And using a similar modified rom on another lens you get weird behavior based on focus distance?

Have you tried the 00 in place of 80 for another lens?

Can you send me the rom from the modified lens?

Duc-Driver · 09-29-2017, 06:35 AM

yes - that's sadly what I mean.
It doesn't matter if it's "00" or "80" - the 50-135 screwdrive does work with "00" too.

And yes - his lens is working over the entire range with screwdrive but same lensrom doesn't work with my 60-250 for entire range --> it must be a (small) hardware hack!
He also tested with isolated sdm contacts and didn't see any errors like I when I isolated the sdm contacts, that speaks again for a hardware hack.

**UncleVanya** · 09-29-2017, 06:38 AM

Originally posted by Duc-Driver

yes - that's sadly what I mean.
It doesn't matter if it's "00" or "80" - the 50-135 screwdrive does work with "00" too.

And yes - his lens is working over the entire range with screwdrive but same lensrom doesn't with my 60-250 --> it must be a (small) hardware hack!

Dang - I wish we could get the info. Did you try his exact rom? Or just modify yours to be similar?

Duc-Driver · 09-29-2017, 06:49 AM

I tried the exact rom without modifying it and also modified mine with the "00" values - but it doesn't matter..same problem as before.

Maybe someone should send his sdm broken 60-250 to russia and analyze what they did

**manishved** · 12-12-2017, 03:23 PM

reviving this thread: Any updates on this one? I have a 60-250 that needs this special treatment.

Duc-Driver · 12-13-2017, 12:59 PM

no, I'm sorry - couldn't get screwdrive to work properly instead of sdm

**UncleVanya** · 12-13-2017, 02:46 PM

Originally posted by Duc-Driver

no, I'm sorry - couldn't get screwdrive to work properly instead of sdm

So far as I know only the russian conversion works in screw drive and we have no idea what they did to the lens.

Duc-Driver · 12-14-2017, 04:28 AM

yes - but it's clear, that it was not only done by editing the lens from...
there have to be a (small?) hardware modification but I don't want to disassemble my working 60-250 for testing

Rhombuss · 12-22-2017, 05:52 PM

Just a quick question for those who have done the conversion: does it actually improve the AF speed and accuracy of the lens?

I have my 16-50 and 50-135 that I got in late 2009, and both still work fine *fingers crossed*. I haven't intensely used them much over the years, mainly just for vacations and some family events. The 16-50 definitely needs a bit of a "wake-up" when I haven't used it for a while, and manually throwing the focus off so that the AF can engage always works. But the SDM itself has never failed. I just find the AF speed sluggish on the 16-50 (definitely in low light conditions). So although my SDM is still fine, and considering it's been 8 years maybe I just lucked out, I'm curious if converting to screw drive would improve things overall.

Thanks in advance for any responses!

**UncleVanya** · 12-22-2017, 06:42 PM

Originally posted by Rhombuss

Just a quick question for those who have done the conversion: does it actually improve the AF speed and accuracy of the lens?

I have my 16-50 and 50-135 that I got in late 2009, and both still work fine *fingers crossed*. I haven't intensely used them much over the years, mainly just for vacations and some family events. The 16-50 definitely needs a bit of a "wake-up" when I haven't used it for a while, and manually throwing the focus off so that the AF can engage always works. But the SDM itself has never failed. I just find the AF speed sluggish on the 16-50 (definitely in low light conditions). So although my SDM is still fine...

For a long night time I had no data. Then someone sent me a working SDM lens with very odd focus problems. It would fail to lock in low light when other lenses on the same body would work fine.

After conversion the lens focused quickly and accurately. So it CAN make a huge difference but I can't say for sure in your specific case.

Rhombuss · 12-22-2017, 08:00 PM - **1 Like**

Originally posted by UncleVanya

For a long night time I had no data. Then someone sent me a working SDM lens with very odd focus problems. It would fail to lock in low light when other lenses on the same body would work fine.

After conversion the lens focused quickly and accurately. So it CAN make a huge difference but I can't say for sure in your specific case.

Just did the conversion on my 16-50. It seems faster; not sure if it's just psychological because the focusing sound is louder and the tactile response is tricking my mind. Will definitely give it a try in various conditions. Either way, it's nice to know how easy it is to switch back and forth. Thanks to the OP for this very easy and simple guide!

Out of curiosity, has anyone assessed or compared battery life with SDM vs screw drive?

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09-26-2017, 12:09 PM	#76
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,454	Originally posted by mattb123 KEH did an initial repair that failed again after a few months. I sent it back to them and they decided they couldn't fix it and refunded that initial repair cost. They said maybe Precision would have more luck but I've been hesitant to put more money into it so instead I put that money toward a Tamron 70-200/2.8 because I needed to cover that range for an upcoming paid shoot. I'm now just holding on to the 60-250 in hopes that an inexpensive fix or conversion might come along but I'm not holding my breath. I really like the size, handling, and rendering of that lens as well as the peace of mind WR gives. Well darn. That was my only idea. Even without AF that's a pretty nice lens. But there are less bulky options if AF is not required. So sorry that this lens is orphaned - I have searched for an answer but I haven't found one yet. Ideally if Pentax would just make it an option to switch between SDM and Screwdrive on these lenses using a body configuration based on lens serial id it would solve all the problems for at least newer bodies.

09-26-2017, 12:53 PM	#77
mattb123 Site Supporter Join Date: Apr 2010 Location: Colorado High Country Photos: Gallery Posts: 10,873	Originally posted by UncleVanya Well darn. That was my only idea. Even without AF that's a pretty nice lens. But there are less bulky options if AF is not required. So sorry that this lens is orphaned - I have searched for an answer but I haven't found one yet. Ideally if Pentax would just make it an option to switch between SDM and Screwdrive on these lenses using a body configuration based on lens serial id it would solve all the problems for at least newer bodies. I'd be thrilled if I could do that on the K-1. I have other options for that range now so the lens just sits.

09-28-2017, 11:30 PM	#78
yucafrita Veteran Member Join Date: Oct 2015 Posts: 459	For the 60-250, what would happen if one takes out the SDM contacts from the mount or stick a tape over it? Would this trigger the lens to use the screw-drive and still communicate properly to the camera body via the other contacts? it's just an idea since I dont have the 60-250 (but considering it). In a german Pentax forum a user mentions that C0 has to be changed at two positions but he cant remember where he read this. Does this ring a bell?

09-29-2017, 12:49 AM	#79
Duc-Driver Forum Member Join Date: Feb 2014 Photos: Gallery Posts: 87	a guy from russia send me his 60-250 rom with working screwdrive. It was modified at a russian repair center. But that lensrom has the same mod like we know with changing "C0" to "80" (ok, at this lens it's changed to "00" but that doesn't matter) - so there have to be a (small) hardware hack. Small because he have not paid that much for that conversation. If you isolte the sdm contacts and use a modified lensrom, autofocus is working between 1,1m to 2,5m and 5m to 10m. That is also the range if you only use a modified lensrom with sdm contacts...in this range screwdrive is working but if you go over it - for example 3m - the lens switches to sdm. With isolatet contacts and if you go for example to 3m, the body gives some error by blinking display - if you go back to 1,1m all is normal again. So there is some error while focusing over the range from 1,1m to infinity...something is given a wrong data or something like that to the camera. I tested that with my K20D and my K3 - on both it's the same. Maybe you have to disconnect the sdm engine or something like that but you have to dissassemble the lens a bit (and mine is still working so far). I would to that (test that) with a failed 60-250, but not with my good one. Originally posted by UncleVanya Ideally if Pentax would just make it an option to switch between SDM and Screwdrive on these lenses using a body configuration based on lens serial id it would solve all the problems for at least newer bodies. that would be very nice but Pentax will never do this because then they don't get money for a damaged sdm Last edited by Duc-Driver; 09-29-2017 at 12:55 AM.

09-29-2017, 06:22 AM	#80
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,454	Originally posted by Duc-Driver a guy from russia send me his 60-250 rom with working screwdrive. It was modified at a russian repair center. But that lensrom has the same mod like we know with changing "C0" to "80" (ok, at this lens it's changed to "00" but that doesn't matter) - so there have to be a (small) hardware hack. Small because he have not paid that much for that conversation. If you isolte the sdm contacts and use a modified lensrom, autofocus is working between 1,1m to 2,5m and 5m to 10m. That is also the range if you only use a modified lensrom with sdm contacts...in this range screwdrive is working but if you go over it - for example 3m - the lens switches to sdm. With isolatet contacts and if you go for example to 3m, the body gives some error by blinking display - if you go back to 1,1m all is normal again. So there is some error while focusing over the range from 1,1m to infinity...something is given a wrong data or something like that to the camera. I tested that with my K20D and my K3 - on both it's the same. Maybe you have to disconnect the sdm engine or something like that but you have to dissassemble the lens a bit (and mine is still working so far). I would to that (test that) with a failed 60-250, but not with my good one. that would be very nice but Pentax will never do this because then they don't get money for a damaged sdm I'm lost a bit by this reply. Are you saying the modified lens from Russia works just fine over the entire range? And using a similar modified rom on another lens you get weird behavior based on focus distance? Have you tried the 00 in place of 80 for another lens? Can you send me the rom from the modified lens?

09-29-2017, 06:35 AM	#81
Duc-Driver Forum Member Join Date: Feb 2014 Photos: Gallery Posts: 87	yes - that's sadly what I mean. It doesn't matter if it's "00" or "80" - the 50-135 screwdrive does work with "00" too. And yes - his lens is working over the entire range with screwdrive but same lensrom doesn't work with my 60-250 for entire range --> it must be a (small) hardware hack! He also tested with isolated sdm contacts and didn't see any errors like I when I isolated the sdm contacts, that speaks again for a hardware hack.

09-29-2017, 06:38 AM	#82
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,454	Originally posted by Duc-Driver yes - that's sadly what I mean. It doesn't matter if it's "00" or "80" - the 50-135 screwdrive does work with "00" too. And yes - his lens is working over the entire range with screwdrive but same lensrom doesn't with my 60-250 --> it must be a (small) hardware hack! Dang - I wish we could get the info. Did you try his exact rom? Or just modify yours to be similar?

09-29-2017, 06:49 AM	#83
Duc-Driver Forum Member Join Date: Feb 2014 Photos: Gallery Posts: 87	I tried the exact rom without modifying it and also modified mine with the "00" values - but it doesn't matter..same problem as before. Maybe someone should send his sdm broken 60-250 to russia and analyze what they did

12-12-2017, 03:23 PM	#84
manishved Loyal Site Supporter Join Date: Mar 2008 Location: N. Calif Photos: Gallery \| Albums Posts: 3,652	reviving this thread: Any updates on this one? I have a 60-250 that needs this special treatment.

12-13-2017, 12:59 PM	#85
Duc-Driver Forum Member Join Date: Feb 2014 Photos: Gallery Posts: 87	no, I'm sorry - couldn't get screwdrive to work properly instead of sdm

12-13-2017, 02:46 PM	#86
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,454	Originally posted by Duc-Driver no, I'm sorry - couldn't get screwdrive to work properly instead of sdm So far as I know only the russian conversion works in screw drive and we have no idea what they did to the lens.

12-14-2017, 04:28 AM	#87
Duc-Driver Forum Member Join Date: Feb 2014 Photos: Gallery Posts: 87	yes - but it's clear, that it was not only done by editing the lens from... there have to be a (small?) hardware modification but I don't want to disassemble my working 60-250 for testing

12-22-2017, 05:52 PM	#88
Rhombuss New Member Join Date: Nov 2014 Posts: 7	Just a quick question for those who have done the conversion: does it actually improve the AF speed and accuracy of the lens? I have my 16-50 and 50-135 that I got in late 2009, and both still work fine fingers crossed. I haven't intensely used them much over the years, mainly just for vacations and some family events. The 16-50 definitely needs a bit of a "wake-up" when I haven't used it for a while, and manually throwing the focus off so that the AF can engage always works. But the SDM itself has never failed. I just find the AF speed sluggish on the 16-50 (definitely in low light conditions). So although my SDM is still fine, and considering it's been 8 years maybe I just lucked out, I'm curious if converting to screw drive would improve things overall. Thanks in advance for any responses!

12-22-2017, 06:42 PM	#89
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,454	Originally posted by Rhombuss Just a quick question for those who have done the conversion: does it actually improve the AF speed and accuracy of the lens? I have my 16-50 and 50-135 that I got in late 2009, and both still work fine fingers crossed. I haven't intensely used them much over the years, mainly just for vacations and some family events. The 16-50 definitely needs a bit of a "wake-up" when I haven't used it for a while, and manually throwing the focus off so that the AF can engage always works. But the SDM itself has never failed. I just find the AF speed sluggish on the 16-50 (definitely in low light conditions). So although my SDM is still fine... For a long night time I had no data. Then someone sent me a working SDM lens with very odd focus problems. It would fail to lock in low light when other lenses on the same body would work fine. After conversion the lens focused quickly and accurately. So it CAN make a huge difference but I can't say for sure in your specific case.

12-22-2017, 08:00 PM - 1 Like	#90
Rhombuss New Member Join Date: Nov 2014 Posts: 7	Originally posted by UncleVanya For a long night time I had no data. Then someone sent me a working SDM lens with very odd focus problems. It would fail to lock in low light when other lenses on the same body would work fine. After conversion the lens focused quickly and accurately. So it CAN make a huge difference but I can't say for sure in your specific case. Just did the conversion on my 16-50. It seems faster; not sure if it's just psychological because the focusing sound is louder and the tactile response is tricking my mind. Will definitely give it a try in various conditions. Either way, it's nice to know how easy it is to switch back and forth. Thanks to the OP for this very easy and simple guide! Out of curiosity, has anyone assessed or compared battery life with SDM vs screw drive?