Putting back the focusing helicoid of an ISKRA

[Lamda]

Hello RF friends,

I have recently purchased an ISKRA that had issues with its shutter (stuck on a single speed and a few other issues...).

I took it apart and managed to restore the shutter to 100% (was very very dirty). In the process of dismantling the unit, I also took apart all the focusing components, i.e. the barrel with the distance indications and the focusing helicoid (= a nice all brass big helicoid). These were also very very dirty and I think that it was good that I took them apart because they were in bad need of a good stripping down, cleaning and re-lubricating.

Now, I have the shutter all in one piece again (with its lenses on) and I need to put the focusing mechanism back in (NB: the ISKRA focuses by moving the entire unit and not just the front element). Obviously, the lens must be adjusted for infinity focusing but now that I look at all this, I am perplexed and cannot work out how to put everything back in and then adjust it for infinity.

Has anyone any experience with this and can assist?

Regards.

 

[jnoir]

When removing, I usually mark the point where it fully disengages, for using it when remounting. Since you did not do that, I'm afraid most likely you're bound to trial and error until you get it.

Are you sure also that you did not miss any "spacer" behind the shutter assembly? Tipically, lenses and shutters were factory-adjusted to the body when mounted, and sometimes a few "shims" (sometimes made out of copper, most of the times out of paper) where needed.

 

[Lamda]

I do have all the spacers that are used behind the shutter when mounted on the camera. All the components that I removed are there.

I do expect that trial & error will be required to get it right at infinity (by using a ground glass at the film plane). However, what I am struggling with is the way the focusing components need to be assembled. It is a slightly peculiar focusing mechanism...

 

[Ernst Dinkla]

I do have all the spacers that are used behind the shutter when mounted on the camera. All the components that I removed are there.

I do expect that trial & error will be required to get it right at infinity (by using a ground glass at the film plane). However, what I am struggling with is the way the focusing components need to be assembled. It is a slightly peculiar focusing mechanism...

There is at least a small correction screw at the front of the focusing mechanism to get the lens and rangefinder in line as a last step. If there was initially no fault there you could use the rangefinder to find out where the helicoil should get in. There are some pictures from a service manual on the web if I recall it correctly. Could be that it shows the assembly as it should be.

Ernst Dinkla