Adjusting shutter curtain tension on a Contax IIa and IIIa

[stan_1]

Does anyone know of a youtube video or a website that shows how to adjust the tension of the first curtain? I know the second curtain can be adjusted with that screw on the side that rolls the entire lower curtain roller. But how can I decrease the tension for the first curtain?

 

[stan_1]

Does anyone know how to do it?

 

[ic-racer]

Have you seen this drawing from the internet?

 

[stan_1]

Have you seen this drawing from the internet?

View attachment 385268

Thanks, thats already a first step, but I thought so far. So how can i decrease the central spring tension without affecting the other 2?

 

[ic-racer]

I don't think you can (alter the springs individually).

 

[Mr Flibble]

I don't think you can (alter the springs individually).

Yep, you can't change them individually. The whole thing runs on one roller with tree individual springs (as per the drawing).
if the gap size changes on the higher speeds and/or the upper curtain does not close fully on slower speeds, than you do not have enough tension on the entire roller .

When tension is too low the shutter curtain straps will slip through the friction buckles in the lower curtain.

 

[stan_1]

But shouldn't there be a way? I read somewhere that it is common that with age you have to tension the roller more and more to get the speeds to the normal timing (otherwise they become too short). In my case I got the timings right but I think the tension is very high, because the sound is quite loud, normaly the contax IIIa should be more quiet I think. How can that be remedied? Or do I have to disassemble the roller to clean the springs or eventually shorten the central spring to get more pressure on the first curtain compared to the second?

 

[flavio81]

But shouldn't there be a way? I read somewhere that it is common that with age you have to tension the roller more and more to get the speeds to the normal timing (otherwise they become too short). In my case I got the timings right but I think the tension is very high, because the sound is quite loud, normaly the contax IIIa should be more quiet I think. How can that be remedied? Or do I have to disassemble the roller to clean the springs or eventually shorten the central spring to get more pressure on the first curtain compared to the second?

Hi,

I repair cameras and work on those models so I can contribute.

This is my advice:

1. Don't increase curtain tension
2. Don't
3. Never increase curtain tension
4. Why would you want to increase curtain tension?

Ok, so you want to diminish curtain tension. Great. Read on.

If this is a IIIa "color dial" model it will always be louder than a "black dial" model simply because there is an additional mechanism that fires before the shutter fires. However, i have a very late producction IIIa that is whisper quiet, so just take this paragraph with a grain of salt.

If the camera is loud or the shutter sound is a "quack" then it definitely has way too much tension. Also, too much tension will "uncap" the 1/1250 speed but its real speed will be way lower, between 1/300 and 1/700. This is, apparently, because too much tension creates friction which in turn slows down the mechanism.

Now, what you want is to have all rotating surfaces clean and lubricated so the shutter works fine with the lowest tension possible. I would recommend you to get, as a target, to have an accurate 1/25 speed. I would also advise you not to change any calibration on the machine!

I would also advice not to bother if you don't get the 1/1250 to work. It is better to have a machine that can have good 25,50,100,250 speeds with low tension, you will get a quieter machine that will last forever.

For the spring tension, there is only one adjustment, there is no individual curtain tension. This due to the design of the shutter, which verges into genius.

Now, to reach the shutter tension adjustment to REDUCE tension, follow this video:
(NOTE: Ignore the advice on the video that suggests to increase tension. The author is a servant of the devil.)



at 4:13 you see the adjusting screw. You can move it to increase tension. To DECREASE tension you need to lift the plate that holds this screw still. Do this while you hold the screw with a screwdriver, otherwise all tension will release abruptly and you don't want that.

Remember to increase tension slowly (increase, test, test, test) because the shutter will require quite a few actuations until the curtain tension stabilizes. That is why there is a way to increase tension without having to disassemble the camera; so you can increase it little by little through days or hours until you get the desired result.