Contax IIa/IIIa and the capping problem.

[Grytpype]

I have three Contax IIa, and three IIIa, in various states of decrepitude. Every once in a while I think I'd like to get one working.

The first one I attempted (a black-dial IIIa) had the usual problem of capping at 1/1250 and 1/500 and only partial exposure at 1/250. I stripped it totally, all but the spring-roller in the curtain assembly, and reassembled it clean and lubricated. It capped at 1/1250 and 1/500 and only partially exposed at 1/250! I guessed that this was because I had not gone all the way into the spring roller, and decided that since it could provide the parts I needed to complete three of my other cameras, this one was more valuable as spares, and abandoned it.

I've now partly stripped another black-dial IIIa with exactly the same fault. Looking back at the notes I made last time, I am reminded of what a nightmare contraption the 'curtain-frame' module is on these cameras, and I am tempted to screw the thing back together and forget about it.

Can anyone tell me whether it is possible to get these cameras working properly without fully dismantling the curtain-frame?

 

[Gregm61]

A 100% working Contax is a thing of beauty. I have such a IIA Black Dial, purchased fully serviced from Henry Scherer in December 2014. When I am out shooting FP4, 1/250, 1/500 and 1/1250 are about the only shutter speeds I am using so for those to not be working property makes the camera fairly useless for any film faster than ISO 100.

I've read enough about the Contax shutter to know I'd not care to be trying to deal with it myself, and adjusting the high speeds requires making certain adjustments or they'll not work right. He goes through a somewhat in-detail description of a IIA/IIIA shutter service on his website. You might check it out.

http://www.zeisscamera.com/services_overhaul-cIIa-body.shtml#Shutter Accuracy Today

http://www.zeisscamera.com/services_overhaul-cIIa-shutter.shtml

 

[Grytpype]

A 100% working Contax is a thing of beauty.

I'm sure you are right. I have an early ('P' prefix) IIa that as far as I can see just needs the rangefinder vertical (and horizontal) alignment sorting out. The shutter seems to work perfectly, though I haven't checked accuracy. It sounds so beautiful it's almost worth what it cost me just to listen to it! They are beautifully made inside as well, but the pre-war II and III are much easier to deal with, and a better shutter design in my opinion.

 

[Grytpype]

Just checked a previous question I posted here when I was assembling the first IIIa, and I have remembered it wrongly. It was actually the upper curtain spindle I could not get into on that one. It had rather a rough curtain assembly (frayed ribbons etc), so it wasn't a good example.

The curtain-frame module does look better on this one. I may just try leaving it intact and cleaning the rest of the mechanism.

 

[Highway 61]

Can anyone tell me whether it is possible to get these cameras working properly without fully dismantling the curtain-frame?

A IIa or IIIa which persists into severe capping at the highest speeds in spite of a full cleaning of the shutter drivetrain, including an ultrasonic cleaning of the beveled gears module (once you have removed the curtains unit from the upper casting) isn't worth the time you're going to have consumed in it.
From experience I can tell that QC issues are the culprit - like you, I once worked for a very long time on a IIa shutter which never ever wanted to get back into a proper working condition. On properly assembled cameras with very precisely machined parts, a basic cleaning of the shutter drivetrain gears and a proper detensioning and retensioning of the first curtain drum roller must be enough to be sucessful at getting the camera work properly at all speeds. This is what happened on the IIa I kept eventually (a very early 1950 model). I have serviced it in 2007 and it's still working perfectly at all speeds now.
I think that Henry Scherer has accumulated a large amount of spare parts over years, and that he can replace the whole shutter units on cameras which are in need of it.
The IIa and IIIa shutters rely on a very complex beveled gears drivetrain on which too much friction apply. The least machining defect there will lead to a shutter which will never work at high speeds because the two shutter curtains won't travel within the proper time gap. With a 24x36 focal plane shutter travelling vertically you can't have the least bit of tolerance.
Let's keep in mind that Hubert Nerwin's team began to work on the Contax IIa prototype during the war, to make a camera with a less complex and more reliable shutter than the II. Peter Henning once sent me some pics of that prototype. It seems that the IIa blueprints were destroyed altogether with the Zeiss Ikon plant under the RAF bombs in Feb. 1945. Hence the camera being released in 1950 in Stuttgart. In the meantime the shutter design flaws hadn't been corrected and the camera marketed in 1950 was very close to the wartime prototype, with all its design flaws.
There is also the shutter crate problem (not machined deep enough on some models so that the first shutter curtains will bounce and will be another capping source).
Best thing is to try to get one that works consistently and regularly after a very routine service, and to remain stuck to it. If you collect them, chances are that about 3/5 will have that impossible-to-fix high speeds problem, were they IIa or IIIa, black dial or color dial.

 

[Grytpype]

Thanks for the information. Actually I am a little more optimistic now about this camera.

I haven't dismantled anything beyond taking the mechanism out of the body, and I have been playing with the spindle tension, and I am seeing some exposure at 1/500 and 1/1250. You have advised me previously to concentrate on the 1/25 sec speed, and there I am getting 29ms, 37ms, and 41 ms across the frame. At 1/500 it is one stop fast and at 1/1250 I am seeing about .3ms.

I'm always rather scared of overtensioning shutter springs. Henry Scherer says that in these cameras increasing tension decreases speed, and to begin with it did, but the last few clicks don't seem to have helped, and I have lost count of how much I have added, so I think tomorrow I'll let the tension down and start again.

 

[Grytpype]

Well, I have a sort of a result. With the curtain springs tightened 30 clicks from the point where the slack in the first curtain is taken up, 1/500 second is 1/500 - but only at the end of frame. The start of frame is about 1/1000. The same fading is present on the other speeds, but of course it becomes less noticeable as the speeds get slower. 1/1250 sec is faster than 1/500, but not a lot! Slow speeds are very accurate.

When these cameras start to cap, they seem do do so at the start of frame, so this one is probably on its way, but at the moment it will produce an exposure at all speeds, so when I've finished de-fungusing all the optics I will screw it together and save my dismantling efforts for one where there is no alternative.

 

[mikyor1]

amazing. I cant imagine doing that with such a over engineered piece of camera. Take some pictures! I'd love to see your progress.

 

[Highway 61]

Well, I have a sort of a result. With the curtain springs tightened 30 clicks from the point where the slack in the first curtain is taken up, 1/500 second is 1/500 - but only at the end of frame. The start of frame is about 1/1000. The same fading is present on the other speeds, but of course it becomes less noticeable as the speeds get slower. 1/1250 sec is faster than 1/500, but not a lot! Slow speeds are very accurate.

This is fairly typical for this shutter. This is why the best thing is to find one that provides even exposure at all speeds with the least amount of tensioning, with high speeds being slightly slower than what they should be, and dismiss the 1/1250 which will never be faster than 1/700 or something. As far as you don't shoot slides (and shooting slides nowadays has become seldom anyway), no big deal.

 

[Grytpype]

Good advice. When I have cleared the decks I'll have a look at the 'P' prefix IIa I mentioned, that does sound very good. It may be just the RF I need to sort out.

It's a shame they are such difficult cameras for the amateur to fix.

 

[Highway 61]

It's a shame they are such difficult cameras for the amateur to fix.

Pro repairmen aren't more successful at them than skilled amateur repairers actually.

 

[rick oleson]

I didn't have to dismantle mine as far as you did, but it took about 6 months to sort it - it would work fine, then start capping again a few weeks after each attempt. The trick, I think, is that the vertical bevel-gear shafts at the top are very short, and it's hard to get to the bearings to properly clean and lubricate them.... so it runs OK when wet and then hangs again as the bearings dry out again. It seems to be these bearings that cause the problem, with the bevel gears imposing a high side load on the bearings in what is already an overly complex gear train. Once I did finally get it working right, though, it stayed good and has not had problems over many years.

When I tested the speeds (some time back now), 1250 was spot on, 500 and 250 a bit fast, and the rest all within 1/3 stop of the indicated speeds.

 

[Grytpype]

The trick, I think, is that the vertical bevel-gear shafts at the top are very short, and it's hard to get to the bearings to properly clean and lubricate them.... so it runs OK when wet and then hangs again as the bearings dry out again. It seems to be these bearings that cause the problem, with the bevel gears imposing a high side load on the bearings in what is already an overly complex gear train.

On the first (now abandoned) IIIa, I did get the bevel-gear spindles stripped down, cleaned and lubed with watch oil, but I don't think it helped much. It was quite clean to start with. My biggest mistake was trying to get into the curtain spindles, which makes this job on a ContaxII/III/Kiev seem an absolute doddle!

I've just been playing with this camera again to see if I could get anything out of it before I steal its focus-mount to use on this second one (bought without), and I get exposure at 1/100, but nothing faster.

Misassembly definitely cannot be ruled out, though!

 

[rick oleson]

That's a lot of disassembly, I've never gone in that deep.

 

[Grytpype]

Well, you have answered my question. Obviously it is (sometimes) possible to get these cameras working properly without dismantling the curtains!

Edit 20/3/17:

Thought I had better add a postscript to this thread in case anyone in the future finds themself using it as a guide to Contax tensions. I have not used the IIIa mentioned above because I felt the shutter was VERY LOUD compared with others, and I was pretty sure it must be overtensioned. The centre-spring on these cameras is very much beefier than the equivalent part in the pre-war cameras and although 30 clicks of tension is only just over one turn (26 clicks/turn) it is definitely much too much.

I've now stripped and rebuilt a IIa, and I find that I get the best results with just 2 clicks of tension from the point where the first curtain has taken up all its slack. The shutter sounds very nice and gives speeds accurate to well within half a stop.

This isn't the place to go into details, but I'll mention the following:

I did not attempt to strip or clean the "curtain-frame" assembly, except as far as needed to swap the 1st curtain and cords for those from a spares camera, because the originals were very lop-sided.

Before detaching the curtain-frame from the top-casting make very sure you have marked the position of all the gears clearly so that you can reassemble them in exactly the same position.

The most essential part of the job is cleaning the bevel gear spindles and their bushings in the top casting. They are not difficult to remove, provided you can make some simple tools. Mark the positions of all the parts at the top of the spindles before dismantling them. The pins fixing the hubs to the spindles are quite easy to get out.

 

[richardHaw]

sorry for reviving this old thread. i just realized something while working on my 2nd 2/3a shutter. I found that the meshing on the top bevel gears is very important, it is best to treat this shutter like a watch from the 50s and experiment with gear meshing,etc. 😱😱😱

what I realized is this, when mating the shutter crate back to the gear train, while on the uncharged state the 1st curtain gears have to be turned all the way and the 2nd curtain gear will have to be 1-tooth short from the limit.

this gave me the much-desired working speeds at the lowest tension possible. I am not sure if this is a manufacturing difference type of situation because just like with watches that were hand-made, each shutter mechanism or movement in the case of watches will behave differently.

can anybody just confirm what I just said? i am in no way a contax expert but i am getting more comfortable with them the more time i spend working with these. mr Hughway61 and the others have been very helpful in showing me around. i am more of a nikon repair hobbyist so the contax world is very different to me.