Minolta MD 35-135/3.5-4.5: Rear lens and aperture register cleaned

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Andreas Thaler

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This Minolta zoom is a recurring patient.

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Its rear lens had already become cloudy and the aperture transmission often got stuck when the tube was pulled out.

Here is my report on the service from December 2023 describing how I cleaned the lens:



Today I took the zoom again to clean the rear lens. I also wanted to permanently solve the problem with the aperture transmission.

Let's go!



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Removing the bayonet ring and dismantling the optical unit which contains the rear lens.


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Heavy fog has formed again on the inside of the rear lens. I suspect it is caused by the lubrication of the helicoids turning into oil.


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The lever that moves the aperture blades in the aperture register. It jerks and does not move smoothly. Although the aperture blades are dry, I suspect that it is a problem with oil contamination.


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Oil and old grease can be seen everywhere in the tube where it doesn't belong.


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Remove the rear second optical unit above the aperture.

First loosen it with the spanner wrench and then unscrew it securely with the plastic Spudger from iFixit.


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Using the lens suction tool, I lift the optical unit out of the tube.


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Here I put a few drops of Zippo lighter fluid, which spread instantly over the aperture blades.


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After moving the aperture over the lever for some time and dabbing off the Zippo, I carefully dried the aperture blades with the Dremel Versatip butane gas burner.

I opened the aperture at intervals to use the Versatip to remove the Zippo condensate caused by the heat from the lens underneath.


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Then I cleaned the lens.

To keep the aperture open against spring pressure, I made a gag out of a piece of rolled-up paper tissue, which I secured with adhesive tape.


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Preparing small pieces from a Zeiss optics cleaning cloth.


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I use a glass rod to apply some isopropyl alcohol to a piece of cloth. This allows me to measure the amount.
 
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Andreas Thaler

Subscriber
Joined
Nov 19, 2017
Messages
4,863
Location
Vienna/Austria
Format
35mm
16.jpg


The lens is now clean and the aperture closes without any problems.


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The optical unit returns to its place.


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Removing the rear lens.


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The convex side on which the fog sits points towards the front lens.


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Ever since I scratched one of the (soft!) front lenses of a Minolta telephoto lens while cleaning it, I use the pointed probe to check whether the surface is scratch-resistant.


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Cleaning again with isopropyl alcohol.


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There remains a slight cloudiness at the edge, which probably comes from lens separation. There is nothing that can be done about this.


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Assembling and installing the rear optical unit with the cleaned lens.

With the lens suction tool, the optical unit can not only be inserted but also screwed in.


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Two spacer rings have their place under the lens bayonet.
 
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Andreas Thaler

Subscriber
Joined
Nov 19, 2017
Messages
4,863
Location
Vienna/Austria
Format
35mm
31.jpg


The zoom is ready for use again. But I will probably have to service it again after a while because the oil remains in the tube.

To solve the problem permanently, I would have to completely disassemble the zoom and clean it. Or try to clean it partially disassembled.

Both of these jobs I avoid based on my previous experience.

The probability is too high that I will not be able to put the lens back together or will have problems with the adjustment. In addition, all lenses must be removed beforehand for cleaning with partial disassembly, which is not always possible without risk.


+++

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

Subscriber
Joined
Nov 19, 2017
Messages
4,863
Location
Vienna/Austria
Format
35mm
The grease on the helicoids that turns into oil is a nuisance. It paralyzes the aperture, clouds lenses with its fumes and shines out from under the bayonet, where it is only annoying but at least does no harm.

I assume that the vast majority of MF lenses are now affected by this. But it does not have a negative effect on all of them.
 
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Andreas Thaler

Subscriber
Joined
Nov 19, 2017
Messages
4,863
Location
Vienna/Austria
Format
35mm
I am prepared for this type of repetitive service work to increase with my inventory of MF lenses.

The intervention involving removing the bayonet ring and dismantling rear lenses should generally pose a low risk.

However, the complete dismantling of a (zoom)lens to clean and re-lubricate is different.

Cleaning and re-lubricating in a partially disassembled state remains an option, but I would not do either with a valuable lens.

And hiring a professional to do it would exceed my budget. The question is also who would actually accept such an order.
 
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