Minolta MD Tele Rokkor 135/2.8 (II): Restored from total loss

[Andreas Thaler]

A 135 from the collection of defective lenses that I brought into the house some time ago.

It had been through a lot or a lot had been done to it.

The aperture blades are no longer in place.

The rear lens is heavily dirty.

A dent on the filter thread was obviously roughly bent with pliers

Overall the lens is a total loss.

So there is a lot to do

---

Aperture register repair

I dismantle the lens from the back to access the loose aperture blades.

Bayonet and aperture ring

The rear lens

After unscrewing the rear optical assembly, the chaos in the aperture register becomes visible.

Apart from a small dent, the aperture slats are not bent and can be removed.

But they have to be reinstalled from the front.

To do this, the front optical unit can be unscrewed.

The components of the aperture register without aperture blades.

Cleaning the inside of the tube from oil and dirt.

 

[Andreas Thaler]

The lever for transferring the aperture settings, which are set via the aperture ring, is only seated loosely in the cover ring of the aperture register. This means that an exact transfer of the aperture values to the aperture blades is not possible.

I decide to try soldering and build a makeshift holder out of a rubber cylinder, a bar magnet and a cleaning brush.

Despite scraping off the top layer at the soldering point and using plenty of flux, the solder does not want to bind.

But it's enough to fix the lever.

The remaining flux could prevent the aperture blade from moving freely above it.

I smooth the solder joint with the Dremel Stylo plus brass round brush.

Mounting the aperture blades.

On the right is an identical second MD 135/2.8, which serves as a reference.

 

[Andreas Thaler]

The cover ring adjusts the aperture opening and is fixed using three adjusting screws (one of which is hidden in the picture).

View from the rear.

The transmission lever is now firmly seated and is already placed on its spring.


When I compare it with my second reference lens, I see that the aperture is slightly adjusted when the tube is extended.

This is not intended and is because the transmission lever is slightly different from its intended position.

I leave it that way because in practice it doesn't result in any restrictions.

At the infinity position, the aperture opening is slightly larger than at minimum close distance. However, the individual aperture gradations are formed evenly in both cases. This means that no exposure errors are to be expected.

It is possible that shots will be slightly more exposed at infinity because all aperture openings are slightly larger, but this should not be an issue with negative film.

The camera receives the preselected aperture values via a cam on the aperture ring and assumes that the aperture openings are correctly formed in the lens.

If I wanted to correct that, I would have to bend the transmission lever, but I prefer a stable connection via the solder joint.

One of the three adjusting screws for the aperture register.


Cleaning and assembly of the rear optical unit

Both lens surfaces of the unit are greasy.

I can remove most of the mess with isopropyl alcohol.

Since the unit cannot be separated, I cannot remove dirt between the lenses.

But the result is overall satisfactory.


Final assembly and correction of the filter thread

Aperture ring and catch cleaned and lightly lubricated.

To make it easier to screw in the front optical assembly, I apply some Ballistol universal oil to the thread.

I use the filter ring vise to correct the dented filter ring as best I can.

A small, light hammer is also used.

The rubber coating on the focus ring is best pulled on with strong, large tweezers.

I touch up the bare areas on the filter thread with glossy black paint.

I wasn't able to rebuild the tele, but to get it back to a fully working condition

 

[Andreas Thaler]

Conclusion

• Today I would better try not to solder the lever for transferring the aperture settings but to attach it with epoxy adhesive. This should allow for a tighter connection and a finer correction until the glue sets.
• Minor limitations in the function of the lens are acceptable to me, given the previous status.
• Nevertheless, in a follow-up project I replaced the entire aperture register and aperture mechanism on the bayonet ring with perfect ones from another MD 135/2.8:

Minolta MD Tele Rokkor 135/2.8 (II): Make one out of two

Recently I dedicated myself to the second Minolta MD Tele Rokkor 135/2.8 (II) from my collection of defective lenses. The rear lens surfaces of this example were also massively dirty. Unfortunately, in this case I was unable to achieve satisfactory cleaning. The optical assembly retained a...

www.photrio.com

+++

All information provided without guarantee and use at your own risk.

 

[koraks]

Despite scraping off the top layer at the soldering point and using plenty of flux, the solder does not want to bind.

No. If the parts were made of silver or copper, it would have worked, but they're obviously not.
It might have worked with silver soldering ('hard' soldering). This requires higher temperatures and uses silver as the solder (as opposed to tin or a tin/lead leger). Only works if the parts fit like clockwork, which does indeed seem to be the case, so it would have been a possibility. A micro propane torch would have likely worked for such small parts.

 

[Andreas Thaler]

No. If the parts were made of silver or copper, it would have worked, but they're obviously not.
It might have worked with silver soldering ('hard' soldering). This requires higher temperatures and uses silver as the solder (as opposed to tin or a tin/lead leger). Only works if the parts fit like clockwork, which does indeed seem to be the case, so it would have been a possibility. A micro propane torch would have likely worked for such small parts.

I would then have to set up a forge

This could be possible with the Dremel Versatip butane gas burner. But that's where I draw the line, I'm not equipped for this kind of work.

 

[koraks]

I would then have to set up a forge

Yes, it sounds pretty spectacular - and in a way, it is.
Mind you, I've never done it myself, but I've assisted my father a couple of times as he did it. The key things are to ensure perfect contact between the parts, removal of any surface corrosion/paint etc. and flux. Much like soldering copper pipe and whatnot, the silver just flows in there pretty much by itself as the piece hits the right temperature.

 

[Andreas Thaler]

A good point. What are the limits for DIY?

As I stated with the Tamron 35-70, metalworking options would be important to deal with stuck screws, broken threads, or missing parts. You can learn how to do this, and the necessary devices should also be affordable for private users. But the problem is the place where you work.

I have a workshop trolley that contains my things. For each project I re-set the table in the kitchen. Everything has to be put away in the evening.

There are neighbors who I don't want to bother with noise. Turning on the big Dremel every now and then isn't a problem, but you can't do it all the time.

Therefore, I limit myself to work that is possible within this framework. Anything electronic, for example, only gets loud when I swear

 

[Andreas Thaler]

Yes, it sounds pretty spectacular - and in a way, it is.
Mind you, I've never done it myself, but I've assisted my father a couple of times as he did it. The key things are to ensure perfect contact between the parts, removal of any surface corrosion/paint etc. and flux. Much like soldering copper pipe and whatnot, the silver just flows in there pretty much by itself as the piece hits the right temperature.

This is goldsmith work. Fascinating!

My father was a wood carver, carpenter and artist, I grew up in his workshops, there were all kinds of tools including large carpentry machines. I look back fondly on it, almost anything was possible for him and I learned a lot from observation, even if I didn't become a craftsman.

 

[Andreas Thaler]

And while we're on the subject of reflection:

For me it's important to stand behind your own work 100 % and to take responsibility for it, regardless of whether it's successful or not.

Learning from others is important, but once you have decided to do it this way and that, then you are the father of your project. And stand by it.

Therefore, I won't get involved in discussions about whether this or that was right or not. I listen to everything and then go through it on my own. The next day I may work differently - or not.

This makes me a loner and not a team player; I may appear stubborn and unteachable. But that's only me as long as I have the screwdriver in my hand

Don't ask my wife about that ...