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Zoom ring binding on an MD Zoom Rokkor 35-70, 3.5
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PostPosted: Sun Jul 23, 2023 10:16 pm    Post subject: Zoom ring binding on an MD Zoom Rokkor 35-70, 3.5 Reply with quote
Hi! I recently acquired this lens and been loving it so far! My only gripe with it is the zoom ring binding when I adjust downwards from 70mm. It feels like it's almost stuck at that position but I can still get it to break free and turn. After that it feels smooth-ish, however there's still slight grinding type noises to be heard while turning. Can anyone who's familiar with these lenses help me out with this issue? My copy is on of the earlier version of this model afaik. It has no macro mode and has the rokkor branding on it. Here are some photos:

https://imgur.com/a/ZwHahnP

Thanks in advance!


PostPosted: Mon Jul 24, 2023 9:59 am    Post subject: Reply with quote
I did service this lens once but I can't recall the exact construction details.

Some obvious possible problems spring to mind, which unfortunately all require a disassembly of the lens:

1) dirt/sand got underneath the zoom control ring
2) a loose screw got into the works
3) one of the inner zoom cams has become loose, which means the cam can tilt and jam inside the cam slot
4) the thread-lock on the retainer ring for the rotating inner zoom barrel has failed and the retainer ring can now rotate and lock up the zoom mechanism

Based on your description my best guess would be problem 3)

If you are not familiar with servicing lenses yourself, the bad news is that a service is probably going to cost you more than another good copy of this lens.


PostPosted: Mon Jul 24, 2023 3:40 pm    Post subject: Reply with quote
Agree that it's likely number 3, BUT on a lot of these zooms, depending on how deep the loose cam post is, you can sometimes just take the grips off and see the offending one, in which case it's often pretty easy to screw it back in, provided the bushing hasn't been mangled in the cam slot.

RokkorDoctor wrote:
I did service this lens once but I can't recall the exact construction details.

Some obvious possible problems spring to mind, which unfortunately all require a disassembly of the lens:

1) dirt/sand got underneath the zoom control ring
2) a loose screw got into the works
3) one of the inner zoom cams has become loose, which means the cam can tilt and jam inside the cam slot
4) the thread-lock on the retainer ring for the rotating inner zoom barrel has failed and the retainer ring can now rotate and lock up the zoom mechanism

Based on your description my best guess would be problem 3)

If you are not familiar with servicing lenses yourself, the bad news is that a service is probably going to cost you more than another good copy of this lens.


PostPosted: Mon Jul 24, 2023 6:38 pm    Post subject: Reply with quote
BrianSVP wrote:
Agree that it's likely number 3, BUT on a lot of these zooms, depending on how deep the loose cam post is, you can sometimes just take the grips off and see the offending one, in which case it's often pretty easy to screw it back in, provided the bushing hasn't been mangled in the cam slot.


Absolutely, on this lens the focus grip can be taken off, and then the cover with focus mark and IR markers comes off after undoing three screws; that gives access to to some of the cams. But I don't know how familiar the OP is with that kind of work; it requires re-collimation for starters.

Minolta's zoom cams are a pain in the butt by the way; they are made up of three parts (the post, then on top of that a calibrated bushing and screw. The post can be nigh impossible to undo; they tend to be thread-locked into the zoom barrel and no amount of solvent or heat will release them. The factory service manuals I have of a few Minolta zooms indicate that whole zoom cam assembly as unserviceable ("DO NOT DISASSEMBLE"), and I can see why; I would say of the Rokkor zooms I have serviced 7 out of 10 times I cannot get all the posts unscrewed, and unfortunately sometimes they all do need to come out to be able to service the inner zoom lens groups properly.

Of course the problem here may be that a post has come loose, in which case it could be screwed back in.


PostPosted: Tue Aug 22, 2023 6:12 pm    Post subject: Reply with quote
RokkorDoctor wrote:
I did service this lens once but I can't recall the exact construction details.

Some obvious possible problems spring to mind, which unfortunately all require a disassembly of the lens:

1) dirt/sand got underneath the zoom control ring
2) a loose screw got into the works
3) one of the inner zoom cams has become loose, which means the cam can tilt and jam inside the cam slot
4) the thread-lock on the retainer ring for the rotating inner zoom barrel has failed and the retainer ring can now rotate and lock up the zoom mechanism

Based on your description my best guess would be problem 3)

If you are not familiar with servicing lenses yourself, the bad news is that a service is probably going to cost you more than another good copy of this lens.


Hi, appreciate the detailed response, thank you very much! Apologies for my late reply, been busy with some real-life issues.

So I've managed to disassemble the lens following this guide I found online:

https://diediemustdive.wordpress.com/2016/12/03/minolta-md-zoom-35-70mm-f3-5-disassembly-and-cleaning/

It's written for a newer version of the lens but the innards seem to be the same. The name plate in my case was probably glued on and I had to use some tiny dabs of acetone to get it to loosen up enough to be removed with a lens spanner. Anyway, here's where I am right now:

https://imgur.com/a/LJuiNBB

I managed to remove all 3 posts but there is another one made out of brass which seems to be quite on there.

The zoom ring turns perfectly smooth when the lens is rested on it's rear element. But pointed horizontally, it binds when I try to turn it from 70 downwards. In fact when the lens is set to a focal point below 50, it can still be set to a wider focal length smoothly. The problem seems to occur when I'm at a focal length higher than 50, and want to set a wider one. It seems to bind then when pointed horizontally. This behaviour persists even with the posts removed. How should I proceed from this point on?

Btw, there also seems to be a threaded shim around the zoom helicoid, which can be turned with a lens spanner. I'm guessing this is for rear focus adjustment?

https://imgur.com/a/MnHPVUc

Thanks in advance, the help is much appreciated!

PS: I did take photos and mark the separation points of the helicoids so hopefully the focus will be fine, but if not I guess we'll cross that bridge when we get to it 😉.

Last edited by Shutterbug07 on Tue Aug 22, 2023 6:39 pm; edited 3 times in total


PostPosted: Tue Aug 22, 2023 6:13 pm    Post subject: Reply with quote
BrianSVP wrote:
Agree that it's likely number 3, BUT on a lot of these zooms, depending on how deep the loose cam post is, you can sometimes just take the grips off and see the offending one, in which case it's often pretty easy to screw it back in, provided the bushing hasn't been mangled in the cam slot.

RokkorDoctor wrote:
I did service this lens once but I can't recall the exact construction details.

Some obvious possible problems spring to mind, which unfortunately all require a disassembly of the lens:

1) dirt/sand got underneath the zoom control ring
2) a loose screw got into the works
3) one of the inner zoom cams has become loose, which means the cam can tilt and jam inside the cam slot
4) the thread-lock on the retainer ring for the rotating inner zoom barrel has failed and the retainer ring can now rotate and lock up the zoom mechanism

Based on your description my best guess would be problem 3)

If you are not familiar with servicing lenses yourself, the bad news is that a service is probably going to cost you more than another good copy of this lens.


Hi! Thanks for chiming in, please see my response above with some new developments.


PostPosted: Tue Aug 22, 2023 7:27 pm    Post subject: Reply with quote
Shutterbug07 wrote:
RokkorDoctor wrote:
I did service this lens once but I can't recall the exact construction details.

Some obvious possible problems spring to mind, which unfortunately all require a disassembly of the lens:

1) dirt/sand got underneath the zoom control ring
2) a loose screw got into the works
3) one of the inner zoom cams has become loose, which means the cam can tilt and jam inside the cam slot
4) the thread-lock on the retainer ring for the rotating inner zoom barrel has failed and the retainer ring can now rotate and lock up the zoom mechanism

Based on your description my best guess would be problem 3)

If you are not familiar with servicing lenses yourself, the bad news is that a service is probably going to cost you more than another good copy of this lens.


Hi, appreciate the detailed response, thank you very much! Apologies for my late reply, been busy with some real-life issues.

So I've managed to disassemble the lens following this guide I found online:

https://diediemustdive.wordpress.com/2016/12/03/minolta-md-zoom-35-70mm-f3-5-disassembly-and-cleaning/

It's written for a newer version of the lens but the innards seem to be the same. The name plate in my case was probably glued on and I had to use some tiny dabs of acetone to get it to loosen up enough to be removed with a lens spanner. Anyway, here's where I am right now:

https://imgur.com/a/LJuiNBB

I managed to remove all 3 posts but there is another one made out of brass which seems to be quite on there.

The zoom ring turns perfectly smooth when the lens is rested on it's rear element. But pointed horizontally, it binds when I try to turn it from 70 downwards. In fact when the lens is set to a focal point below 50, it can still be set to a wider focal length smoothly. The problem seems to occur when I'm at a focal length higher than 50, and want to set a wider one. It seems to bind then when pointed horizontally. This behaviour persists even with the posts removed. How should I proceed from this point on?

Btw, there also seems to be a threaded shim around the zoom helicoid, which can be turned with a lens spanner. I'm guessing this is for rear focus adjustment?

https://imgur.com/a/MnHPVUc

Thanks in advance, the help is much appreciated!

PS: I did take photos and mark the separation points of the helicoids so hopefully the focus will be fine, but if not I guess we'll cross that bridge when we get to it 😉.


Difficult to give advise from here on; as I said it has been a while since I serviced one of these MD 35-70 lenses.

Those posts can be impossible to take out; if one or more of them won't come out relatively easily then it is unlikely you will able to unscrew it. They tend to be thread-locked in place and you cannot get enough heat into the post to soften the thread-lock without danger of damaging the inner optics. Even a small butane torch directed directly onto the post won't allow you to budge it; I have tried myself more than once, the inner lens cradle wicks away the heat too quickly for the thread-lock to soften enough, and you can't heat up the whole inner lens cradle as the optics will be damaged. Acetone seems to do nothing on the type of thread-lock used for the posts.

At this stage one important thing to check is whether the retainer ring holding the rotating zoom barrel in place isn't loose.

Look at the front of your part-disassembled lens. You will notice the front rim seems to indicate three concentric layers. The middle "layer" is actually a retainer ring and it has two slots for a lens spanner. This ring holds the rotating part of the zoom mechanism in place and this retainer ring is screwed almost tight in the factory such that the zoom cam barrel can still rotate freely, and then this retainer ring is fixed in place with a small amount of thread-lock. If this thread-lock has failed (possible e.g. when the lens has been dropped) then this retainer ring will be loose and will be free to rotate as the zoom mechanism is operated. In one direction the zoom mechanism will then rotate freely, in the other direction it will have a tendency to lock up. So check this retainer ring isn't loose. If that is the problem it can be easily fixed by rotating the retainer ring a little counter-clockwise until the zoom moves freely again, and then fix the retainer ring in its new position with some new thread-lock. You may be able to see where the old thread-lock was applied originally.

Good luck! Like 1 small


PostPosted: Tue Aug 22, 2023 7:59 pm    Post subject: Reply with quote
RokkorDoctor wrote:
Shutterbug07 wrote:
RokkorDoctor wrote:
I did service this lens once but I can't recall the exact construction details.

Some obvious possible problems spring to mind, which unfortunately all require a disassembly of the lens:

1) dirt/sand got underneath the zoom control ring
2) a loose screw got into the works
3) one of the inner zoom cams has become loose, which means the cam can tilt and jam inside the cam slot
4) the thread-lock on the retainer ring for the rotating inner zoom barrel has failed and the retainer ring can now rotate and lock up the zoom mechanism

Based on your description my best guess would be problem 3)

If you are not familiar with servicing lenses yourself, the bad news is that a service is probably going to cost you more than another good copy of this lens.




Hi, appreciate the detailed response, thank you very much! Apologies for my late reply, been busy with some real-life issues.

So I've managed to disassemble the lens following this guide I found online:

https://diediemustdive.wordpress.com/2016/12/03/minolta-md-zoom-35-70mm-f3-5-disassembly-and-cleaning/

It's written for a newer version of the lens but the innards seem to be the same. The name plate in my case was probably glued on and I had to use some tiny dabs of acetone to get it to loosen up enough to be removed with a lens spanner. Anyway, here's where I am right now:

https://imgur.com/a/LJuiNBB

I managed to remove all 3 posts but there is another one made out of brass which seems to be quite on there.

The zoom ring turns perfectly smooth when the lens is rested on it's rear element. But pointed horizontally, it binds when I try to turn it from 70 downwards. In fact when the lens is set to a focal point below 50, it can still be set to a wider focal length smoothly. The problem seems to occur when I'm at a focal length higher than 50, and want to set a wider one. It seems to bind then when pointed horizontally. This behaviour persists even with the posts removed. How should I proceed from this point on?

Btw, there also seems to be a threaded shim around the zoom helicoid, which can be turned with a lens spanner. I'm guessing this is for rear focus adjustment?

https://imgur.com/a/MnHPVUc

Thanks in advance, the help is much appreciated!

PS: I did take photos and mark the separation points of the helicoids so hopefully the focus will be fine, but if not I guess we'll cross that bridge when we get to it 😉.


Difficult to give advise from here on; as I said it has been a while since I serviced one of these MD 35-70 lenses.

Those posts can be impossible to take out; if one or more of them won't come out relatively easily then it is unlikely you will able to unscrew it. They tend to be thread-locked in place and you cannot get enough heat into the post to soften the thread-lock without danger of damaging the inner optics. Even a small butane torch directed directly onto the post won't allow you to budge it; I have tried myself more than once, the inner lens cradle wicks away the heat too quickly for the thread-lock to soften enough, and you can't heat up the whole inner lens cradle as the optics will be damaged. Acetone seems to do nothing on the type of thread-lock used for the posts.

At this stage one important thing to check is whether the retainer ring holding the rotating zoom barrel in place isn't loose.

Look at the front of your part-disassembled lens. You will notice the front rim seems to indicate three concentric layers. The middle "layer" is actually a retainer ring and it has two slots for a lens spanner. This ring holds the rotating part of the zoom mechanism in place and this retainer ring is screwed almost tight in the factory such that the zoom cam barrel can still rotate freely, and then this retainer ring is fixed in place with a small amount of thread-lock. If this thread-lock has failed (possible e.g. when the lens has been dropped) then this retainer ring will be loose and will be free to rotate as the zoom mechanism is operated. In one direction the zoom mechanism will then rotate freely, in the other direction it will have a tendency to lock up. So check this retainer ring isn't loose. If that is the problem it can be easily fixed by rotating the retainer ring a little counter-clockwise until the zoom moves freely again, and then fix the retainer ring in its new position with some new thread-lock. You may be able to see where the old thread-lock was applied originally.

Good luck! Like 1 small


Hi again, thanks for getting back to me so swiftly!

So, I managed to get 3 of the posts out, the ones that hold the focusing helicoid, but this last post has a different mount than the others, it seems to be made of brass and probably on there permanently. The others were quite easy to remove and they also had bushings on them.

Is all I can do at this stage is to check the retainer ring? I can't see any way to disassemble the zoom helicoid further. The brass mount seems to be acting like a stop for the helicoid.


PostPosted: Wed Aug 23, 2023 8:31 am    Post subject: Reply with quote
Shutterbug07 wrote:
Hi again, thanks for getting back to me so swiftly!

So, I managed to get 3 of the posts out, the ones that hold the focusing helicoid, but this last post has a different mount than the others, it seems to be made of brass and probably on there permanently. The others were quite easy to remove and they also had bushings on them.

Is all I can do at this stage is to check the retainer ring? I can't see any way to disassemble the zoom helicoid further. The brass mount seems to be acting like a stop for the helicoid.


You probably won't get much further.

Do bear in mind that in Minolta's own service manuals I have myself and in other ones I have seen, the zoom barrel/mechanism is usually marked as "DO NOT DISASSEMBLE" and "NO SUPPLY".

These zoom lenses are already from an era where optics were no longer meant to be taken apart for a full service; cosmetic parts could be changed of course, but glue had started to replace some screwed fixings, lens groups now more often had burnished mounts, zoom cams were fixed for life, the inner optics of zooms often were not meant to be serviceable. I doubt that even Minolta's own service engineers were meant to take the zoom barrels apart.

Of course with the warranty long expired, DIY enthusiasts can do/try what they like and some zoom mechanisms can be taken apart, others can't. Sometimes it is simply pot-luck as to how much thread-lock was used on these mechanisms, or how tight a particular factory worker has tightened a screw. Sometimes these 30+ year old lenses come apart completely, sometimes they don't...

40+ and certainly 50+ year old lenses are a different matter, they can often be fully disassembled for service, down to the individual lens groups, although optical centering during re-assembly may be an issue for some, and floating focus mechanisms may need additional lens-specific calibrated setting tools to adjust.


PostPosted: Wed Aug 23, 2023 3:11 pm    Post subject: Reply with quote
just bought one of these zooms without macro and, at the beggining focus ring was working very smooth and suddenly it is blocked, no way to move the focus ring, is stuck to infinity, and it was working very very smooth just an hour before. is there any trick to solve it out?
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