DA* 50-135 - Focusing ring won’t focus manually

haroon88 · 10-06-2022, 09:32 AM

Hi everyone,

I got myself a second hand defective Pentax DA* 50-135 lens. I found out that the focusing ring won’t focus the lens manually. Also the automatic focus won’t work which clearly is the famous SDM fault but this manual focus thing seems strange to me. Do you think it can be easily repaired? The SDM issue can be resolved by the usual screw drive installation thing through pk tethering but I want to know about the focus ring issue. Kindly help. Thanks

**FozzFoster** · 10-06-2022, 10:19 AM

maybe something is jammed up with the quickshift mechanism? I really don't know..
might sounds crazy but maybe give it a really good smack (percussive maintenance).
also, try autofocusing (continuous focusing with camera) while briskly rotating the focus ring back and forth.

https://youtu.be/GzAucMahZP0?t=44

Not a Number · 10-06-2022, 10:22 AM

I believe there are some gears in focusing mechanism of the lens that can break. And turning the manual focus ring without switching the lens and/or body to manual focus can also damage the mechanism.

Seems likely one or more of the gears are broken and perhaps the SDM as well. If you can get the parts the gear can be replaced by a competent repair person.

77me · 10-06-2022, 10:25 AM

After sitting around for a time, my 50-135 won't manual or auto focus until I exercise the focus ring in manual focus mode. After I rack the focus a few times the clutch starts to engage and focusing starts to work again. For me it is not a SDM issue. It squeaks, but does focus once the clutch starts working again.

**c.a.m** · 10-06-2022, 10:34 AM

Originally posted by haroon88

Do you think it can be easily repaired? The SDM issue can be resolved by the usual screw drive installation thing through pk tethering but I want to know about the focus ring issue.

My 50-135 was repaired several times in 2012-13 to fix the failed AF. The SDM was replaced twice, and various other repairs were made to the gear mechanism, focus ring, and clutch assembly.

The lens operated properly for a couple of years after the fourth warranty repair, but then the AF failed again and the manual focus jammed. I converted it to screwdrive. Since then, both AF and MF have functioned well.

- Craig

haroon88 · 10-06-2022, 12:23 PM

Thanks for the replies. Since it is a very cheap copy I got (40€ only), I’ll do some aggressive actions like exercising the focus ring just to see if it works. For reference, I have uploaded one video to show the problem to all. Tomorrow I’ll also take it to local camera shop to get an opinion for repair.

Focus ring 50-135 - YouTube

Thanks

AfterPentax Mark II · 10-06-2022, 01:16 PM

Originally posted by haroon88

Thanks for the replies. Since it is a very cheap copy I got (40€ only), I’ll do some aggressive actions like exercising the focus ring just to see if it works. For reference, I have uploaded one video to show the problem to all. Tomorrow I’ll also take it to local camera shop to get an opinion for repair.

Focus ring 50-135 - YouTube

Thanks

If you look carfully you will notice that the ring containing the window moves while the focusing ring is turned. When turned to the right you will see that the white indication mark turns back to 70, while at the start of the video it is just passed 70 to a higher zoom rate. I think it was sold for parts...

haroon88 · 10-06-2022, 09:59 PM

Originally posted by AfterPentax Mark II

If you look carfully you will notice that the ring containing the window moves while the focusing ring is turned. When turned to the right you will see that the white indication mark turns back to 70, while at the start of the video it is just passed 70 to a higher zoom rate. I think it was sold for parts...

Actually that is just the zoom ring getting rotated while I try to rotate the focus ring with one hand. Nothing uncommon here.

AfterPentax Mark II · 10-07-2022, 02:13 AM

Originally posted by haroon88

Actually that is just the zoom ring getting rotated while I try to rotate the focus ring with one hand. Nothing uncommon here.

I looked at it several times trying to see if the zoom ring was being moved, but I did not see that. Hence my remark.

10-06-2022, 09:32 AM	#1
haroon88 Senior Member Join Date: Nov 2017 Posts: 143	*DA 50-135 - Focusing ring won’t focus manually** Hi everyone, I got myself a second hand defective Pentax DA* 50-135 lens. I found out that the focusing ring won’t focus the lens manually. Also the automatic focus won’t work which clearly is the famous SDM fault but this manual focus thing seems strange to me. Do you think it can be easily repaired? The SDM issue can be resolved by the usual screw drive installation thing through pk tethering but I want to know about the focus ring issue. Kindly help. Thanks

10-06-2022, 10:34 AM	#5
c.a.m Site Supporter Join Date: Jan 2013 Location: Ottawa, Canada Photos: Gallery \| Albums Posts: 4,193	Originally posted by haroon88 Do you think it can be easily repaired? The SDM issue can be resolved by the usual screw drive installation thing through pk tethering but I want to know about the focus ring issue. My 50-135 was repaired several times in 2012-13 to fix the failed AF. The SDM was replaced twice, and various other repairs were made to the gear mechanism, focus ring, and clutch assembly. The lens operated properly for a couple of years after the fourth warranty repair, but then the AF failed again and the manual focus jammed. I converted it to screwdrive. Since then, both AF and MF have functioned well. - Craig Last edited by c.a.m; 10-06-2022 at 10:48 AM.

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10-06-2022, 10:19 AM	#2
FozzFoster Custom User Title Join Date: Jan 2016 Location: Alberta Photos: Albums Posts: 6,808	maybe something is jammed up with the quickshift mechanism? I really don't know.. might sounds crazy but maybe give it a really good smack (percussive maintenance). also, try autofocusing (continuous focusing with camera) while briskly rotating the focus ring back and forth. https://youtu.be/GzAucMahZP0?t=44

10-06-2022, 10:22 AM	#3
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	I believe there are some gears in focusing mechanism of the lens that can break. And turning the manual focus ring without switching the lens and/or body to manual focus can also damage the mechanism. Seems likely one or more of the gears are broken and perhaps the SDM as well. If you can get the parts the gear can be replaced by a competent repair person.

10-06-2022, 10:25 AM	#4
77me Senior Member Join Date: Mar 2015 Photos: Albums Posts: 150	After sitting around for a time, my 50-135 won't manual or auto focus until I exercise the focus ring in manual focus mode. After I rack the focus a few times the clutch starts to engage and focusing starts to work again. For me it is not a SDM issue. It squeaks, but does focus once the clutch starts working again.

10-06-2022, 12:23 PM	#6
haroon88 Senior Member Join Date: Nov 2017 Posts: 143 Original Poster	Thanks for the replies. Since it is a very cheap copy I got (40€ only), I’ll do some aggressive actions like exercising the focus ring just to see if it works. For reference, I have uploaded one video to show the problem to all. Tomorrow I’ll also take it to local camera shop to get an opinion for repair. Focus ring 50-135 - YouTube Thanks

10-06-2022, 01:16 PM	#7
AfterPentax Mark II Pentaxian Join Date: Mar 2021 Posts: 1,467	Originally posted by haroon88 Thanks for the replies. Since it is a very cheap copy I got (40€ only), I’ll do some aggressive actions like exercising the focus ring just to see if it works. For reference, I have uploaded one video to show the problem to all. Tomorrow I’ll also take it to local camera shop to get an opinion for repair. Focus ring 50-135 - YouTube Thanks If you look carfully you will notice that the ring containing the window moves while the focusing ring is turned. When turned to the right you will see that the white indication mark turns back to 70, while at the start of the video it is just passed 70 to a higher zoom rate. I think it was sold for parts...

10-06-2022, 09:59 PM	#8
haroon88 Senior Member Join Date: Nov 2017 Posts: 143 Original Poster	Originally posted by AfterPentax Mark II If you look carfully you will notice that the ring containing the window moves while the focusing ring is turned. When turned to the right you will see that the white indication mark turns back to 70, while at the start of the video it is just passed 70 to a higher zoom rate. I think it was sold for parts... Actually that is just the zoom ring getting rotated while I try to rotate the focus ring with one hand. Nothing uncommon here.

10-07-2022, 02:13 AM	#9
AfterPentax Mark II Pentaxian Join Date: Mar 2021 Posts: 1,467	Originally posted by haroon88 Actually that is just the zoom ring getting rotated while I try to rotate the focus ring with one hand. Nothing uncommon here. I looked at it several times trying to see if the zoom ring was being moved, but I did not see that. Hence my remark.