Zeiss Ikon Contax IIa/IIIa CLA notes

[MarcoIIIc]

I have CLA'd 4-5 of these over the last 10 years or so, and while the information available over the last few years has improved, not much further understanding of the shutter adjustments have emerged since Rick Oleson's excellent drawings and notes now probably a couple of decades old. My first few CLA's went very smoothly but when I started measuring shutter speeds and repairing a few less minty cameras the true complexity of this shutter emerged.

I would like for this thread to focus on the CLA of these masterpieces in mechanical complexity and bounce my understanding off some of you that might have been here already. This because unlike for the other rangefinder from the 50's, commercial repair of these camera is scarce and sometimes ridiculously priced.

There is starting to be a good amount of information available:

• Rick Oleson's Notes
• The official Repair Manual
• A couple of good youtube video.

Now doing a CLA and not getting a shutter to shade at 1/1250 is easy, getting a true (+/-20%) "1250" is the real challenge! Several times I had the impression of getting it right but my actual top speed was in the 1/500s range....

So lets get into the details of shutter speed adjustments, These can be grouped into three settings:

• Slow speeds (1, 2, 5, 10) with full delay escapement engagement.
• Middle speeds (25, 50, 100) partial escapement engagement.
• High speeds (250, 500, 1250) shutter spring tension only.

Let assume that we have properly cleaned and lubricated everything, what influences shutter speeds and their adjustment in each group?

Slow speeds:

• Shutter Spring Tension (sets base curtain travel speed)
• Position of the Slow Speed Cam on 2nd Curtain. (sets engagement of the escapement? not really)
• Any thing else I am missing?

Middle speeds:

• Shutter Spring Tension (sets base curtain travel speed)
• Position of the Slow Speed Cam on 2nd Curtain. (sets engagement of the escapement? not really)
• Position of the 1st Curtain Cam. (sets the curtain "gap" - time between 1st/2nd curtain release)
• Position of the High Speed Cam on 2nd Curtain. (fine tunes the curtain "gap")
• Any thing else I am missing?

High speeds:

• Shutter Spring Tension (sets base curtain travel speed)
• Position of the 1st Curtain Cam. (sets the curtain "gap" - time between 1st/2nd curtain release)
• Position of the High Speed Cam on 2nd Curtain. (fine tunes the curtain "gap")
• Any thing else I am missing?

In true Zeiss Ikon fashion everything is adjustable, now good luck getting there.... As is apparent adjusting one speed group effects all others (fortunately some with minor implications on others...). Here is my working process after the Clean & Lubricate:

I start with the high speeds:

1. Adjust the shutter tension. How much? great question. Wish I had a good answer. I release all tension (from an un-tensioned shutter) and increase tension until I get no shading at 1/500 or I have approached 1/2 a turn of tension from slack. The Zeiss Ikon Manual shows 3/4 turn for tension but it is not very clear to me what the starting point is.
2. I adjust the first curtain cam to get a good measured 1/250s.
3. I get back to tensioning the shutter until the shading at 1/1250 just starts to disappear (max is 3/4 turns!).
4. I measure my 1/250 again.
5. I fine tune the "gap" with the 2nd curtain high speed cam.
6. I measure 1/1250.
7. 1/1250 good then I move on to the slow and middle speeds, if not I go back to point 5 or tweak the shutter tension.

Middle and Slow speeds:

1. Measure what the high speed adjustment got me for middle and slow speeds.
2. Fiddle with the Slow speed cam on the 2nd curtain (and see very little change... if any at all).
3. Ask myself repeatedly if any other ways of adjusting the slow and middle speeds exist.
4. Call it a day, button it up, it's an analog camera that's 50 years old and still provides better images than the other German brand which can be CLA'd and adjusted in 1.5 hours.

Attached are some pictures for your viewing pleasure... Feedback Please!

 

[markjwyatt]

Hi Marcoiiic- on the iia (and likely the iia), there is a large flat screw on where cam fork attached to the bottom of the top body (where the film cannister is loaded). Is that used to adjust spring tension? Can that help with low speed problems?

 

[MarcoIIIc]

Hi Marcoiiic- on the iia (and likely the iia), there is a large flat screw on where cam fork attached to the bottom of the top body (where the film cannister is loaded). Is that used to adjust spring tension? Can that help with low speed problems?

The screw you mention (if I understood you correctly) gives you direct access (without separating the shutter assembly from the rear casting) to the screw tensioning the shutter spring tension. Main problem with doing it this way is that the tension can only be increased. Did ZI provide this as a short cut to fixing the shading shutter at 1250? or for a last minute tension increase adjustment?

Regarding slow speed adjustment, there should be a way to vary the amount of escapement engagement with the second curtain that I have not yet found....

 

[flavio81]

I would like to extend this topic, since I also work on those cameras.

So far, great resources are the following:

1. Contax IIa/IIIa service manuals at learncamerarepair.com
2. Rick oleson notes: http://rick_oleson.tripod.com/index-62.html
3. richardHaw made an excellent vieo on how the shutter works here: https://www.youtube.com/watch?v=5Yqoxe84eIE&t=1135s

Additionally the following threads at this forum have relevant information:

https://www.rangefinderforum.com/node/167304
https://www.rangefinderforum.com/node/134073

(There are more, but so far those two are the most useful)

 

[flavio81]

The screw you mention (if I understood you correctly) gives you direct access (without separating the shutter assembly from the rear casting) to the screw tensioning the shutter spring tension. Main problem with doing it this way is that the tension can only be increased. Did ZI provide this as a short cut to fixing the shading shutter at 1250? or for a last minute tension increase adjustment?

Regarding slow speed adjustment, there should be a way to vary the amount of escapement engagement with the second curtain that I have not yet found....

I'll write on the slow speeds soon...

 

[flavio81]

I would like to continue this thread and thank MarcoIIIc for the initial post, as well as richardHaw , Highway 61 who have contributed on this very topic elsewhere on this forum.

What I would like to cover is something that I feel has been left aside when discussing this cameras, and it's hinted by Richard on his video (URL above). In the video Richard mentions the spring on the slow speeds governor was too weak, thus the governor was running too fast.

I'd like to mention that I had exactly the same problem on my IIa. And there is no way this shutter, on my camera, would be able to reach 1 second speed since the governor was too fast. For me, it's obvious that storing this camera, uncocked, will let this spring be tensioned fully and through decades it might become weaker. So my camera (and Richard's) won't never achieve 1 sec speed unless that spring is brought back to normal force OR the curtain tension is set laughably low.

Thus, I see this is a point that needs to be kept in check before performing the camera adjusment. This spring will affect ALL speeds below 1/250, as per the design. Let's recall:

I
So lets get into the details of shutter speed adjustments, These can be grouped into three settings:

• Slow speeds (1, 2, 5, 10) with full delay escapement engagement.
• Middle speeds (25, 50, 100) partial escapement engagement.
• High speeds (250, 500, 1250) shutter spring tension only.

So, if one has such a "hyperactive" governor, attempting to get accurate 1/25 speed will probably mean curtain tension will be lower than what was designed for this camera.
Additionally, the camera has went through many revisions over its production timeline and I suspect the later 'color dial' models were intended to use a higher tension. Many people report the Color Dial models are louder, this might be due to the added parts for flash sync but i suspect the shutter was beefed-up too.

The choices, thus, are, either try to repair the governor (so it is able to achieve a true 1 sec speed at the 1sec setting), OR re-target the middle speeds for a higher speed, perhaps maybe 30, 60 and 125, or maybe more.

As per the way this mechanism works, my guess would be that the "correct" way of calibrating the shutter, assuming the shutter and gears were properly cleaned and lubricated, as well as the slow speed cam is correctly positioned (= touches completely the governor arm when the shutter is cocked at the 1 sec position, thus giving full possible delay), is as follows:

1. set to minimum tension (which would mean, enough tension to remove slack on bottom curtain)
2. increase tension targeting for achieving correct 1/25 speed (assuming that the governor is NOT "hyperactive")
3. Since 1/50 and 1/100 speeds are obtained by geometrically changing the position of the slow speed cam, they should be correct or close to correct after this adjustment. Otherwise the slow-speed cam might help a bit to achieve adjustment.
4. Very slow speeds (1, 2, 5 and 10) should be close to correct but if they aren't, they don't stand a chance of being adjusted without influencing (3). Thus, this adjustment, IMO, would only be possible by controlling the force of the spring on the governor, or some other clockwork method (**) that i'm not aware of.
5. The fast 1/250 speed now should be tested, the exposure should be even. Now, if the exposure is too short or too long, it ought to be adjusted via changing the position of the high speed cam (there's a screw for that).
6. In theory if the high speed cam is properly adjusted and the curtain tension is correct, then 500 and "1250" speeds should be rather close to correct.

However, as you see in step (2), there's an interaction between the tension of the shutter and the force that is applied on the governor spring, which will influence medium and low speeds.

Thus, what I think, if one has a "speedy" governor, would be to maybe proceed as follows:

- Target 1/30 or 1/40 for the 1/25 setting; and similar offsets for the 1/50 and 1/100 speeds.
- With this curtain tension as a baseline, move the high speed cam to achieve correct 1/250 and 1/500 speed.
- If the 1/1250 speed works and is even 1/2 stop close to the target, then call it a day.

As mentioned by many people, making 1/1250 work correctly without overtensioning the shutter implies not just that the mechanism is perfectly clean and oiled, but also implies that there's not undue wear, corrosion, or manufacturing defect, or improper mating of the shutter case gears with the camera top gears.

Opinions?

(**) methods of possibly altering the delay of the governor:

- increasing the mass of the pendulum?
- increasing the force of the spring that presses the pendulum against the star wheel?

 

[SyPat]

I never tried to manipulate the gears under the top cover. I limited myself to cleaning with a brush soaked in lighter fluid and then lubricating with a watchmaker's oil. I managed to improve the accuracy of the gears by playing on this spring (1250 remains, according to me, a despairing cause), but I especially noticed that after 6 months, the settings had not held well.

The question I have is: has anyone managed to get a setting that is both accurate and reliable over time? I have the impression that it is very difficult to achieve both.

BTW, you say "The Zeiss Ikon Manual shows 3/4 turn for tension", but what is this manual ?

 

[flavio81]

I never tried to manipulate the gears under the top cover. I limited myself to cleaning with a brush soaked in lighter fluid and then lubricating with a watchmaker's oil. I managed to improve the accuracy of the gears by playing on this spring (1250 remains, according to me, a despairing cause), but I especially noticed that after 6 months, the settings had not held well.

This is the shutter curtain tension adjustment and increasing it too much will cause premature failure of your shutter or the curtains themselves.

My camera did work at 1/1250 but the shutter tension was way too high, noticeably high when cocking the camera (compared to other IIa). This is not good at all. The idea is to make the speeds work with the lowest tension possible.

BTW, you say "The Zeiss Ikon Manual shows 3/4 turn for tension", but what is this manual ?

Manual:
https://learncamerarepair.com/produc...2&secondary=23

 

[flavio81]

So lets get into the details of shutter speed adjustments, These can be grouped into three settings:

Marco, revisiting your post, let me offer an edited list:

Shutter speed is influenced by:

• Slow speeds (1, 2, 5, 10): The full delay escapement engagement, with pendulum
• Middle speeds (25, 50, 100) escapement without pendulum (inertial) , which interacts with curtain speed
• High speeds (250, 500, 1250) shutter spring tension (curtain speed) + gap + any friction in the system

Slow speeds: 1 2 5 10:

• Shutter Spring Tension should not influence much at all.
• Position of the Slow Speed Cam on 2nd Curtain. Will influence low and middle speeds.
• Éngagement of the pendulum in the pallet. It seems this can be adjusted. On your picture, you see there's a metal cutaway next to the pendulum. Bending this should set the engagement.On my machine (later color dial) there is a screw that might be an eccentric to set the engagement.
• The cam follower for the speed dial, for the slow/mid speeds, will set how much the escapement is "cocked". This could potentially be adjusted via bending. But will influence low and middle speeds.

Middle speeds: 25 50 100:

• Shutter Spring Tension, which fights against the...
• Main spring on the engagement
• Position of the Slow Speed Cam on 2nd Curtain. Will influence low and middle speeds.
• Position of the 1st Curtain Cam -- shouldn't matter at all.
• The cam follower for the speed dial, for the slow/mid will set how much the escapement is "cocked". This could potentially be adjusted via bending. But will influence low and middle speeds.

High speeds 250 500 1250:

• Shutter Spring Tension (sets base curtain travel speed) - very important
• Any friction in the mechanism (including the curtain itself)
• Position of the 1st Curtain Cam. (sets the curtain "gap" - time between 1st/2nd curtain release)
• Position of the High Speed Cam on 2nd Curtain -- NOTE: here i'm not sure if this should really be adjusted for tuning the gap, OR if the position of the 1st curtain cam should be adjusted either. I guess one of the two should be adjusted, maybe not both.
• Some bad technicians bend the arm that follows the shutter speed dial (high speeds) and sets the position of the cam follower for the high speed cam. This should be checked.

 

[flavio81]

Some additional considerations for these machines:

Since the normal lenses use the camera's helicoid, the focal length must be precise, otherwise focus would only be corrected to be exact at Infinity or close distance, but not both.

Yesterday i was working on a Jupiter-8M, which has easy provision to adjust the lens-to-mount distance (no shimming required, just move a ring). However, it seems my lens doesn't have the correct focal length, so i can get perfect correction at close distances (i.e. 2.5m), but at Infinity it is slightly off. This assessment, based on verifying focus at the film plane using a ground glass.

Does anybody have an idea on how to modify the Jupiter-8m focal distance? If possible. Maybe moving the spacing of the front element??

 

[largedrink]

I would like to extend this topic, since I also work on those cameras.

So far, great resources are the following:

1. Contax IIa/IIIa service manuals at learncamerarepair.com
2. Rick oleson notes: http://rick_oleson.tripod.com/index-62.html
3. richardHaw made an excellent vieo on how the shutter works here: https://www.youtube.com/watch?v=5Yqoxe84eIE&t=1135s

Additionally the following threads at this forum have relevant information:

https://www.rangefinderforum.com/node/167304
https://www.rangefinderforum.com/node/134073

(There are more, but so far those two are the most useful)

Here is another thread, but it seems the images are no longer present. I have the originals saved.
https://www.rangefinderforum.com/node/97927

 

[Pál_K]

Is it possible to repost the photos?

 

[largedrink]

Is it possible to repost the photos?

Here they are (credit to user pb908).

The attachments look to be in random order, but the filenames are numbered.

 

[flavio81]

Here they are (credit to user pb908).

The attachments look to be in random order, but the filenames are numbered.

Thanks! Always very useful.

On some images i read "i cleaned this with WD40". WD40 is a very bad choice for any camera but even worse for this one since it leaves a viscous residue that over time can get more and more viscous. And the shutter needs very light (low viscosity) lubrication.

It needs cleaning of the moving parts with naptha (even better would be an ultrasonic cleaning) and then to apply camera shutter oil (like Nyeoil) in carefully controlled amounts.

Something that is not mentioned but appears to be necessary for achieving 1/1250 with the lowest tension possible is to fully disassemble the shutter spring assembly (lower curtain drum), clean it, and lubricate it. I've yet to do that, but will be attempting it at some point.

Also another thing that is important is to check the shutter ribbon, it shouldn't give friction (i.e. by fraying). Next time i dissassemble one of my Contaxes i'll check if the specs of this ribbon match the one for the old Contax (pre-war) ribbons.

 

[flavio81]

By request from largedrink here's my write-up on Contax IIIa top cover dissasembly. I posted this previously on a repair group.

Contax IIIa camera top removal.

The IIIa top is much harder to remove than the IIa. But not impossible at all.
The procedure can be divided in the following sections:
0. Prepare your mind
1. Remove rewind assembly
2. Remove wind assembly
3. Remove camera top plate
4. Remove meter assembly as a module

DETAIL
0. Prepare your mind: The Contax IIIa was the ultimate evolution of the first professional rangefinder ever, the Contax, This machine was extremely expensive in its day and had the best RF lenses of its day bar none (lol wetzlar). Now it's over 70 years old and thus you will treat it with respect, overwhelming devotion, tender gentleness and loving, geriatric care.

1. Rewind assembly: Remove camera back, unscrew the part that engages the film cartridge (one flathead screw). Remove carefully and take note of where everything is placed. Rewind post can now be pulled out.
Remove film speeds dial, three screws. Everything will come out now, including the base dial with the speed values. Note: for reassembly, you need to make sure the meter coupling lever engages the cam at the underside of the base dial.

2. Wind assembly: Identical to IIa, easy to remove, just remove three screws around wind knob, remove film counter, shutter button, spring, washers (there are also TINY washers under the shutter button). Remove three screws to remove inner wind disc and spring below. Remove shutter speed dial.

3. Camera top plate: Remove camera top screws in plain sight at left and right side (4 in total)
Remove meter top cover plate, 4 tiny screws. Pull it up gently.
Remove meter flap hinge, two screws, be careful. Remove hinge (with flap). If hinge can't be easily removed, loosen accesory shoe screws (4) and windshield screws (3, with locking agent on)
Remove camera top by pulling up gently.

4. Meter assembly
See picture, remove screws 76 and 149. Then, unscrew screw 66320 slowly while slightly pulling the whole module up. Screw 66320 can't be pulled out(removed), and doesn't need to be removed.
DONE, now you have access to the slow speeds mechanism, curtain cams, and you can proceed now identically to the Contax IIa
REMEMBER the maxim of camera repair: "Never force anything!"

 

[largedrink]

Some reference diagrams from The Contax Way, 3rd edition, H Freytag, 1953.

Contax layout



Contax shutter



Contax rangefinder



Contax IIIa meter

 

[Pál_K]

These photos, diagrams, and notes are extremely useful. This thread should be made “sticky”.

 

[flavio81]

Some reference diagrams from The Contax Way, 3rd edition, H Freytag, 1953.

Amazing! Does this book cover servicing the Contax postwar cameras?

 

[dexdog]

last image shows Contax IIIa meter, so yeah covers at least some post-WW2 stuff. Also publication date of 1953 is an indicator.

 

[largedrink]

I'm pretty sure there's no servicing information in the book, I'll check when I get home from work. The main technical diagrams are cutaway lens diagrams, and the ones I posted above. The emphasis of the book is on using the camera. If I find any more useful information I'll post it.