Minolta MD Tele Rokkor 200/4 (II): Lenses cleaned, stiffness fixed

Recently I dedicated myself to this beautiful Minolta MD Tele Rokkor 200(4 (II) from a collection of defective lenses that I had purchased.




There was bad contamination in the rear optical assembly and the focus ring could only be turned the last bit to infinity with gentle force.


I started with the lens problem

Because if the contamination cannot be removed, less work is invested than in the helicoids, which are always demanding when it comes to solving problems.










Dismantling

Heavy oil pollution can be seen.









Removing the aperture ring, the locking ball is secured, oil pollution again to be seen under the ring.







Removing the rear optical assembly.

The contamination of the lens can be clearly seen even without LED illumination.




The components of the rear optical assembly.




X-ray (LED light) check of the affected lens






Cleaning the lens

The sequence isopropyl alcohol - lighter fluid - acetone had no effect.

Even careful scratching with the probe did not help; the contamination remained unaffected.




Only Aqua Purificata finaly removed the stubborn stuff.

Who would have thought that the weakest remedy would work best!

I have no idea what caused this heavy contamination.

Occasionally, fine traces of cleaning can be seen. But compared to the previous situation, these don't matter.

Actually, this shouldn't happen when cleaning with a damp microfiber cloth.

But maybe it wasn't me, because some fine scratches were already visible beforehand.

The assembly of the rear optical assembly went smoothly.



Moving on to problem #2




The focus ring became stiff from this position.

I suspected gummy grease in the worm gear and decided to clean and re-grease the helicoids while they were installed.

This saves having to disassemble the helicoids and the associated adjustment problems afterwards.








Removing the front lenses to avoid contamination during subsequent work.

Two lenses I could not remove.




The syringe, ready to introduce Zippo lighter fluid into the helicoids




Several passes with lighter fluid and turning the helicoids in/out were necessary to remove the old grease enough for the focus ring to rotate almost freely.

However, this did not eliminate the stiffness towards infinity.

Fortunately, none of the oil-lighter fluid emulsion ran into the aperture register and onto the installed lenses.

I let the soup run out of the back of the tube and wiped it off.




After drying with the hot air blower, I stuffed plenty of Castrol LMX Li complex grease between the two helicoids using cleaning sticks. Since the helicoids are flush, I couldn't apply grease directly to the worm gear.

The distribution of the grease on the worm gear was achieved by diligently turning the focus ring and adding grease several times.

And indeed, the stiffness disappeared almost completely

Finally, I removed the excess grease and cleaned the inside of the tube with isopropyl alcohol.














Cleaning and assembly of the rear components.

As always, the rest ball got some of the good, fresh grease

To protect it, the front lens has a plastic ring on which the engraving ring sits after screwing in.




Cleaning service for the front lens.










Finally, I noticed that the red marker for inserting the lens into the camera was missing.

Replacement provided an irreparable 135 mm Minolta lens that donated its point after applying isopropyl alcohol and lifting with the probe.




The Minolta 200 mm now in fine condition

+++

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

Bravo! Great job! Another lens saved from the bin!

Kino said:

Bravo! Great job! Another lens saved from the bin!

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