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Minolta MC-X 1.2/58mm and 1.7/85mm repair
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PostPosted: Mon Jan 24, 2022 6:10 pm    Post subject: Reply with quote
Most impressive.


PostPosted: Mon Nov 21, 2022 9:01 pm    Post subject: Re: Minolta MC-X 1.2/58mm and 1.7/85mm repair Reply with quote
stevemark wrote:
Back in 2017, hidden in a lot of old cameras, I bought a MC 1.2/58mm. While from the outside it looked like new, there was quite a bit of fungus inside. Not only was the space between the front group and rear group affected, but there was also fungus inside the sealed front group. Not much later, together with another Minolta collector (and automotive engineer) we tried to dismantle the front group, albeit without success.

Roughly a year later, again hidden in a lot of old stuff, there was an equally nice looking MC 1.7/85mm. Again, there was a problem - its aperture was stuck open. Since I already had a working MC-II 1.7/85mm and MD 1.7/85mm, I didn't bother to open and clean the newly acquired MC-X 1.7/85mm. Both lenses were shelved and forgotten.

Some days ago I decided to give them another try.

The MC-X 1.2/58mm is pretty straightforward when it comes to removing the front and the rear leans groups. However, opening the sealed front group proved to be a bit tricky: There are two small metal rings keeping the front lens in its position. The first ring has two slots for the spanner wrench, and getting it loose was no problem. The second ring - just beneath the first - obviously is sealed and needs rather more force. It seems that Minolta had a special tool for opening it, since there are four slots instead of the usual two. After some trials, and following the suggestions of Richard Haw, also the second ring came free. Cleaning the inner surface of the first lens was relatively easy, and no traces or damage to the coating was visible. The rear surface of the front group and the first surface of the rear gruoup were only slightly affected by fungus, and easy to clean as well. Reassembling the front group and then the entire lens was no problem. Just be very careful when removing the aperture ring - there's a small metal ball behind it (about 1 mm in diameter!), for "clicking" the aperture. It tends to fly away, pushed by a minute spring ...

Now the MC 1.2/58mm was perfectly clean again - and test images did confirm that its optical formula must slightly derive from the earlier MC-II 1.2/58mm: The MC-II has a distinctively yellowish tint, the colors of MC-X on the other hand are in line with other Minolta lenses. The MC-X is sharper wide open, and it has more longitudinal CAs.


Minolta XM with Minolta MC 1.7/85mm (left) and Minolta X-1 with Minolta MC 1.2/58mm (right), after cleaning

Now having successfully completed the removing of fungus from the 1.2/58mm I thought that cleaning the aperture of the 1.7/85mm would be easy and quickly done. I was wrong, though. More information on that one tomorrow Wink

S


Hi Steve, I've just git a first version of this lens, with iris not opening, even though aperture ring is working, it also got plenty of dust ,bit of haze and some small spots of fungus. To acces iris , is it necessary to open the whole lens including helicoidal etc? Or would be enough to remove front and rear groups ? I understand this first version has got very sensitive coatings, how could I remove fungus without damaging the coatings, as rinsing the elements I'm not sure would totally remove small spots of fungus (I've never tried it)


PostPosted: Mon Nov 21, 2022 10:39 pm    Post subject: Re: Minolta MC-X 1.2/58mm and 1.7/85mm repair Reply with quote
kiddo wrote:

Hi Steve, I've just git a first version of this lens, with iris not opening, even though aperture ring is working, it also got plenty of dust ,bit of haze and some small spots of fungus. To acces iris , is it necessary to open the whole lens including helicoidal etc? Or would be enough to remove front and rear groups ?

I don't know whether the mechanical construction of the MC-II and the MC-X 1.7/85mm is identical. If you have "freed" the aperture block from the helicoids, you may try to clean it by rinsing with plenty of a solvent such as acetone. In my case i didn't work, however, since the aperture blades were partly covered with a tar-like substance. I had to dismantle everything.

kiddo wrote:
I understand this first version has got very sensitive coatings, how could I remove fungus without damaging the coatings, as rinsing the elements I'm not sure would totally remove small spots of fungus (I've never tried it)

I would try a very soft paper and a few dops of detergent in about 100ml of water. That always worked for me, without damaging the coatings. There was one single exception, however - a wartime coated Carl Zeiss Jena Sonnar 1.5/5cm which had extremely sensitive inner coatings (outer coatings were no problem).

You might also try an alcohol such as propanol or iso-propanol.

S


PostPosted: Tue Nov 22, 2022 1:12 am    Post subject: Re: Minolta MC-X 1.2/58mm and 1.7/85mm repair Reply with quote
stevemark wrote:
kiddo wrote:

Hi Steve, I've just git a first version of this lens, with iris not opening, even though aperture ring is working, it also got plenty of dust ,bit of haze and some small spots of fungus. To acces iris , is it necessary to open the whole lens including helicoidal etc? Or would be enough to remove front and rear groups ?

I don't know whether the mechanical construction of the MC-II and the MC-X 1.7/85mm is identical. If you have "freed" the aperture block from the helicoids, you may try to clean it by rinsing with plenty of a solvent such as acetone. In my case i didn't work, however, since the aperture blades were partly covered with a tar-like substance. I had to dismantle everything.

kiddo wrote:
I understand this first version has got very sensitive coatings, how could I remove fungus without damaging the coatings, as rinsing the elements I'm not sure would totally remove small spots of fungus (I've never tried it)

I would try a very soft paper and a few dops of detergent in about 100ml of water. That always worked for me, without damaging the coatings. There was one single exception, however - a wartime coated Carl Zeiss Jena Sonnar 1.5/5cm which had extremely sensitive inner coatings (outer coatings were no problem).

You might also try an alcohol such as propanol or iso-propanol.

S


Sorry, my bad, i was referring to the 58mm 1.2, as I've got the first version all metal hills and valleys. It's got stuck iris , si I'm not sure if a whole removing helical/aperture ring would be necessary


PostPosted: Tue Nov 22, 2022 5:20 am    Post subject: Reply with quote
Luckily I know a very experienced camera repair man here in The Netherlands that does these kinds of repairs for me for a reasonable price. I've did a few aperture repairs in the past, some with succes, but I killed a few lenses as well 😊. Expensive lenses I usually hand over to the expert.


PostPosted: Tue Nov 22, 2022 10:39 am    Post subject: Re: Minolta MC-X 1.2/58mm and 1.7/85mm repair Reply with quote
kiddo wrote:
stevemark wrote:
kiddo wrote:

Hi Steve, I've just git a first version of this lens, with iris not opening, even though aperture ring is working, it also got plenty of dust ,bit of haze and some small spots of fungus. To acces iris , is it necessary to open the whole lens including helicoidal etc? Or would be enough to remove front and rear groups ?

I don't know whether the mechanical construction of the MC-II and the MC-X 1.7/85mm is identical. If you have "freed" the aperture block from the helicoids, you may try to clean it by rinsing with plenty of a solvent such as acetone. In my case i didn't work, however, since the aperture blades were partly covered with a tar-like substance. I had to dismantle everything.

kiddo wrote:
I understand this first version has got very sensitive coatings, how could I remove fungus without damaging the coatings, as rinsing the elements I'm not sure would totally remove small spots of fungus (I've never tried it)

I would try a very soft paper and a few dops of detergent in about 100ml of water. That always worked for me, without damaging the coatings. There was one single exception, however - a wartime coated Carl Zeiss Jena Sonnar 1.5/5cm which had extremely sensitive inner coatings (outer coatings were no problem).

You might also try an alcohol such as propanol or iso-propanol.

S


Sorry, my bad, i was referring to the 58mm 1.2, as I've got the first version all metal hills and valleys. It's got stuck iris , si I'm not sure if a whole removing helical/aperture ring would be necessary


The 58/1.2 is VERY similar in construction to the 85/1.7, so you can pretty much follow most of the instructions for the 85/1.7 as documented by Stephan (stevemark).

The one big difference is that the 58/1.2 has a slightly more elaborate lens mount construction which contains a ball-race. This lens has 8 screws on the back, alternating long & short ones. The long ones hold the entire mount assembly onto the lens. The short ones hold the ball-race assembly together. Remove two adjacent screws to work out which of the alternating long & short screws are the long ones and which are the short ones. Then put the short one back and proceed to only remove the LONG screws to take off the mount assembly. If you remove the short ones you will be searching the floor for a few tiny balls and spacers. Don't ask how I know this... Sad

The entire aperture assembly separates from the helicoid very much like the 85/1.7 as demonstrated by Stephan.

Good luck.
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