Help putting Chinon 135 together

[Prometheus]

Came apart when I turned the focusring. I've tried, but cant get it together. Maybe there is some other way to dissassamble the correct way first? There are 4 screws at the rear.


IMG_5015 by Mattias Wirf, on Flickr


IMG_5016 by Mattias Wirf, on Flickr


IMG_5017 by Mattias Wirf, on Flickr


IMG_5018 by Mattias Wirf, on Flickr

[roby02091987]

It's very strange that it came apart just by turning the focus ring. It should have locks, just like any other lens.

Well... for now i'll make a "quick" guide, without photos. This afternoon i'll disassemble my lens for further cleaning and i'll take few shots of the process.

Keep in mind that my chinon 135 is a bit different from yours, i have this version:
http://www.blog.bkspicture.com/bilder/review_Auto_Chinon_135mm_f2_8/Auto_Chinon_135mm_f2_8_pic_1.JPG
Maybe their mechanics is the same, maybe it is not, i don't know.

First of all, you need to make things easier by removing the diaphragm control fork (we'll put it in place later).
It's that "fork" thing that you can see in the first two photos, inside the barrel of the lens (the piece on the left in those photos).

To remove this, you need to unscrew the four screws that keep be M42 mount attached to the back of the lens.
Remove those screws and remove the M42 lens mount.

Now, you should have access to the diaphragm ring, simply pull it out, BUT pay a lot of attention to the little sphere that creates those typical "clicks" while you rotate the diaphragm ring. Try to don't lose it.

Then, you have to remove the distance scale ring, which also works as a lock to infinity focus and minimum focus distance.
BEFORE moving this ring, make a mark or sign (or take a photo or both) in order to remember the original position of this ring. It is very imporant because, without a mark, it would be very difficult to regain a lens that focuses to infinity when the focusing ring in on the infinity mark.

Now comes the most tricky part, reassembling the two parts of the lens.

You need first to find the exact point where the lens and the barrel helicoids match together and began to screw one in the other.
But it is not so easy. If you look inside the barrel you'll surely see two little brass planks (i don't know if it is the correct term).
You need this two planks to match exactly those two long holes in the helicoid of the lens.

This is easiest way that i've found:
1) rotate the focus ring on the barrel in order to lower a bit those two brass "planks".
2) Try to screw the lens to the barrel in a point where the brass planks and the holes in the helicoid as close as possible
3) Screw down the lens until it is blocked by those brass planks (you could rotate it just a few degrees).
4) Rotate very, very slowly the focus ring AND the lens in both directions* and try to make the brass planks and the holes in the helicoid match togheter.
5) when they are matched toghether, just rotate the focus ring clockwise in order to screw the lens in the barrel.

* depends by the relative positions of the helicoid holes and brass planks. The brass planks must go into the holes in the helicoid.

Now the most is done. You have just to put the lens back toghether.

First the distance scale/lock ring. Use the mark and the photos you've made earlier to achieve the correct position. Maybe you need to rotate a bit the focus ring to put the distance scale in the correct position.

Then, put back on the diaphragm ring, but pay attention: the "fork" must match a little metal tab that opens and closes the diaphragm.
After you've put it back toghether, try to move the diaphragm ring: the diaphragm should open and close.

Last but not the least, put back on the lens mount.
The easiest way i found is: put the A/M slider in A.
With the diaphragm full open (just for reference), put the lens mount with the little external metal pin diametrically opposed to the actual position of the diaphragm fork.
Now, turn gently the lens mount clockwise by a few degrees, until the lens mount screw holes and the barrel screw holes match*.
Now check the functionality of the A/M switch and, if everything is fine, screw back those four screws and you've finished the job.

*During this operation, the lens mount does a little "jump". It is absolutely normal.

I hope this helps and I hope everything is understandable (english is not my native tongue).

This afternoon, if i can find some time, i'll make some photos.

[Prometheus]

Big thanks, I havent succeeded yet though Since I never used the lens it could be was faulty when I got it (in a larger package), but I'll give it one more attempt later on...