CZJ 5cm F2 Sonnar Collapsible Teardown

[Brian]

It was brought to my attention that there was not an easy to find instructional on the web for this one.

Spare Sonnar and Nikon E3 to the rescue.

My Starting picture, with all tools required for the teardown.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2770

Lens in the collapsed position exposes the set screw that needs to come out.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2771

Remove it:

http://www.ziforums.com/picture.php?albumid=255&pictureid=2772

I use slit rubber gromets for a good grasp. A rubber mouse pad works as well.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2773

Module out.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2774

[Brian]

Rear module comes out with a spanner. Sometimes you get lucky and can use the rubber mat to get it out. Not today...

http://www.ziforums.com/picture.php?albumid=255&pictureid=2775

On the "T" coated lenses under Sn 3M, check for a set screw holding the rear module in. The F1.5 lens has them.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2776

Next remove the set screw from the variable stand-off ring.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2777

Remove it, again I use rubber for the grip.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2778

MAKE SURE TO NOTE THE ORIENTATION! Otherwise, it might not line up with the Tap for the set screw when re-assembling.

[Brian]

Ring is off, remove the coupling screw for the aperture.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2779

Screw Hole for re-assembly.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2781

Aperture ring slides off as a unit.

Look at the side of the name-ring, it has two set screws holding it in. Remove them.


http://www.ziforums.com/picture.php?albumid=255&pictureid=2782

Unscrew the name ring.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2783

[Brian]

The front optic is glass in brass, and is held in by Friction. You will need a soft suction cup, I use one from a Barbie Suncatcher.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2784

Once the front assembly is out, the triplet falls right out.

Don't let it hit the front element!

http://www.ziforums.com/picture.php?albumid=255&pictureid=2785

Aperture can be flood-cleaned.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2786

[Brian]

I use an ice-cube tray to keep the parts in-order for re-assembly.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2787



When re-assembling, the variable stand-off ring MUST re-align with the set-screw Tap. The set screw must be flush with the ring, or the optics module will hang-up when screwing back into the Mount.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2789

The hole for the set screw must line up almost exactly so the set screw goes straight in.

http://www.ziforums.com/picture.php?albumid=255&pictureid=2790

I use a pick with a really sharp end to line the set screw tap up with the hold.

[Brian]

All Done

http://www.ziforums.com/picture.php?albumid=255&pictureid=2791

[dexdog]

Brian, just a note to let you know that your excellent instructions on the tear-down of the Contax 50/2 collapsible also worked on my 50/2 collapsible in LTM. I took the lens apart because it had a fair amount of haze on the lens element immediately in front of the aperture. The exterior lens barrel is aluminum alloy, except the distance ring, which appears to be steel. Interior lens construction is solid brass, very nicely machined and polished.

The lens was interesting, in that I found 3 different serial numbers on the various parts of the lens.

The name ring is serial number 2710478, Thiele delivery date Dec 7, 1942

The front element and the lens group behind it are (2)935597, Thiele delivery date July 31, 1946.

The rear lens group is (2)935688, Thiele delivery date July 31, 1946.

The Theile records show that all of these lens numbers apply to 50/2 lenses built in Contax mount.

In any case, I gently cleaned the lens elements with Windex, flood-cleaned the aperture with Ronsonol, and put it back together. Nice and clear now, no trace of haze. The only tough part was screwing the lens back together, making sure that I did not cross-thread the hard brass interior element into the soft alloy lens body

Thanks!

[Brian]

Good going!

I've never seen a Contax mouint lens with mismatched SN's! I'm thinking this lens was assembled from left over parts, and you've discovered a 1940's "Mad Scientist" hacking lenses! (was not my Dad, he flew B-29's back then)

[dexdog]

Intrigued by the findings of the first collapsible 5cm/2 Sonnar in LTM, I disassembled my other collapsible 5cm/2 in LTM, serial number 2805446, which looks almost identical to the other lens in appearance, choice of materials and workmanship. This lens also had 3 different serial numbers on the components.

(2)805446 on the name ring and front lens element;
(2)805398 on the group behind the front element;
(2)005446 on the rear lens group.

The serial number on the rear lens group is definately odd man out here, given that it would represent a lens number from 1937-1938 era. I wonder if this element was simply misengraved- it would be an easy mistake for a worker to accidentally key in a zero in place of an eight in a stamping machine. If this element were engraved incorrectly (i.e., should have been (2)805446) all of the lens components would share a similar completion date.

This lens was also different from the other one in that it had a shim about 0.5mm thick behind the variable standoff ring.

[Brian]

I vote for misengraved!

I've taken three of the Contax mount uncoated lenses apart to this level- all had matching numbers. I'm thinking things got crazy around the time your lenses were made.