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Iris repair Minolta Rokkor-TC 100 f4
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PostPosted: Sun Sep 05, 2010 11:44 pm    Post subject: Iris repair Minolta Rokkor-TC 100 f4 Reply with quote
While window shopping last night-went beyond the window and bought a dirty beat up looking Rokkor-TC 100mm f4, with the aperture blades all twisted inside. The outside of the lens and front element cleaned up very nicely.

Sorry ,didn't think of taking pictures of the repair except late in the game.Here's what I did:

1: Unscrewed the front cell which is also attached to the front name label.
2:Took three exposed screws that attach the front ring to body .Took front rig off.
3:Unscrewed preset rings and piece underneath it-after some trial and error.
4. Took Minolta lens- mount off and unscrewed the 3 screws holding the helical alignment rod(single).
5. Focused to infinity and unscrewed slotted retaining ring (entering through the back)that holds the back element,and acts as a nut to hold the back end and aperture nest together.
6.Took retaining ring off the back and slid back element out .

At this time the good news was all the lens element were in great shape-no fungi,haze ,cleaning marks. . I managed to pull all 14 blades out one at a time with tweezers and a tooth pick. One blade had a small kink on it-all the studs/rivets were intact. I ironed the bent blade the best I could. I saw no way of pulling the Iris container out-so I proceeded to painstakingly put the blades back in the slot one at a time-only to find out that when there were 5 blades to go -it was impossible for me to go on. I went back now to staring at this container trying to reverse engineer it in my mind. There was a "C" shaped locking ring above the Iris ring that I pried out and the upper lid of the Iris followed out. The bottom part of the iris unscrewed out -I stuck my thumb in the ring and untwisted the container. Now I had the Iris parts out and I was ready to assemble the aperture blades.

Here's when I laid the blades in the wrong orientation:





So I took it apart and put it back in the right orientation and put the top part of the iris over it. I found that fanning it out like the sun's rays was the best way to begin the layering-and I used toothpicks as the tool of choice.







From here on it was a matter of putting things back in the reverse order of dissassembly.










So now I have another working lens in my collection-it may not be rare/sought after , but the time I spent on it was a good exercise in patience/persistence for me Very Happy

Last edited by Kathmandu on Mon Sep 06, 2010 11:36 pm; edited 2 times in total


PostPosted: Sun Sep 05, 2010 11:47 pm    Post subject: Reply with quote
Great! Many thanks for detailed presentation! Congrats!! Self rescued lens always more valuable than others!


PostPosted: Sun Sep 05, 2010 11:57 pm    Post subject: Reply with quote
Thanks Attila, are you familiar with this lens-quality ? Rokkors have a good name but I understand this was built as a cheap lens back then. I am looking forward to taking pictures with this lens. Looks as though it might work great on my bellows if I remove the helical assembly as all the elements are up front.


PostPosted: Mon Sep 06, 2010 12:05 am    Post subject: Reply with quote
Unfortunately my Rokkor experience is still limited , no idea about this lens.I guess you can't go wrong with any 100mm lenses.


PostPosted: Mon Sep 06, 2010 11:04 am    Post subject: Reply with quote
Very well executed - congrats! Rokkor lenses are very good lenses usually. That TC you repaired is an early version with rel. simple lens construction, later ones are certainly better.


PostPosted: Mon Sep 06, 2010 11:40 pm    Post subject: Reply with quote
Attila wrote:
Unfortunately my Rokkor experience is still limited , no idea about this lens.I guess you can't go wrong with any 100mm lenses.


I figured the same too-about 100mm. I also like the looks of this one.

kds315* wrote:
Very well executed - congrats! Rokkor lenses are very good lenses usually. That TC you repaired is an early version with rel. simple lens construction, later ones are certainly better.


I cheated and tested with the lens hand held and I see great potential-Thank you Klaus.


PostPosted: Tue Sep 07, 2010 1:32 am    Post subject: Reply with quote
Excellent job!
Is it supposed to be used with a bellows?


PostPosted: Tue Sep 07, 2010 3:40 am    Post subject: Reply with quote
Himself wrote:
Excellent job!
Is it supposed to be used with a bellows?


Thanks much. Its meant to be used with the Minolta manual focus lens, but since the elements are in the front half, and that half comes apart easy- I am asserting that you could use it on some sort of bellows(any mount) ,and achieve infinity easy. . Very Happy


PostPosted: Tue Sep 07, 2010 4:44 am    Post subject: Reply with quote
Interesting lens. I really can't say much on performance, because I haven't seen test results on this lens.

It's a 3/3 design that came out in 1960. It was considered a bargain lens. There top line lens was the PF 100 which I believe came out in 1961.

It was only made in the MC1 style. There is no later version of this lens.
It was one of Minoltas 1 shot wonders that was made for a few years and discontinued. It was made thru the 1962 model year, possibly a year or so longer.

A cool lens to own. I'm glad you were able to save it. I would like to see some pictures from this lens when your able.
A bargain lens from Minolta dosen't mean a bad lens. Some of there cheap lens perform on par or better then there top line lenses. Smile


PostPosted: Tue Sep 07, 2010 5:08 am    Post subject: Reply with quote
walter g wrote:
Interesting lens. I really can't say much on performance, because I haven't seen test results on this lens.

It's a 3/3 design that came out in 1960. It was considered a bargain lens. There top line lens was the PF 100 which I believe came out in 1961.

It was only made in the MC1 style. There is no later version of this lens.
It was one of Minoltas 1 shot wonders that was made for a few years and discontinued. It was made thru the 1962 model year, possibly a year or so longer.

A cool lens to own. I'm glad you were able to save it. I would like to see some pictures from this lens when your able.
A bargain lens from Minolta dosen't mean a bad lens. Some of there cheap lens perform on par or better then there top line lenses. Smile


Thanks, for your information -it looks like an interesting lens and similar in construction to the Isco-Göttingen Westar 100mm f4.5-(as far as the front end containing all the elements)-giving you adaptability via custom helical assembly to adjust for infinity.I will surely post pictures and sample images. Very Happy


PostPosted: Tue Jun 04, 2013 6:51 am    Post subject: Reply with quote
Unfortunately most of your pictures are gone. Could you re-post them?

I recently tried to service a TC 135mm F4, the larger sister lens. I couldn't figure out to remove the aperture and the pre-set ring. So I hoped your images could help.

Further it would be interesting to classify your lens exactly. I recorded 2 generations with 6 editions so far.


PostPosted: Tue Jun 04, 2013 7:19 am    Post subject: Reply with quote
Dennis wrote:
Unfortunately most of your pictures are gone. Could you re-post them?

I recently tried to service a TC 135mm F4, the larger sister lens. I couldn't figure out to remove the aperture and the pre-set ring. So I hoped your images could help.

Further it would be interesting to classify your lens exactly. I recorded 2 generations with 6 editions so far.


This thread is from 2010 and the life of members moves on - isn't that a "bit overdrawn" to ask for a re-upload just for you??

But nice to see you here... Very Happy


PostPosted: Tue Jun 04, 2013 2:54 pm    Post subject: Reply with quote
kds315* wrote:
This thread is from 2010 and the life of members moves on - isn't that a "bit overdrawn" to ask for a re-upload just for you??

That sounds a bit like this forum has an expiration date and is hosted just for me. Maybe you should think about the WORLD WIDE WEB and its ideas. This is a severe loss of information, without the pictures the benefit of this thread is gone. But if you don't care about the quality of this forum...
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