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CZJ MC S 135 3.5 re-assemble help!
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PostPosted: Sat Oct 22, 2011 9:11 pm    Post subject: CZJ MC S 135 3.5 re-assemble help! Reply with quote
So this is what happened.

I got a reasonably good price on one of these but unfortunately the seller was not able to spot a sticky aperture, stuck to be precise. So I got hold of some screwdrivers and fixed it.

All good until the part where you are supposed to re-assemble the lens. After assembling everything I noticed that after turning the focus ring s couple of inches something happens inside the back of the lens, where the aperture control is, there is a clicking noise and i can no longer decrease the lens extension only increase it.

Also, if I tight the screws of the mount hard enough to keep it securely in place the aperture mechanism will lock and I will not be able to change aperture.

My guess is that the infinity adjustment is badly configured but after several hours (!) I am out of ideas on what I might be doing wrong and since I am dealing with plastic pieces I really am starting to loose confidence in my skill and beginning to fear I might break something rendering the lens useless.

I completely followed the better known tutorial on servicing this lens with the exception of counting the number of turns before removing the infinity adjustment screw.


Please help.


PostPosted: Mon Oct 24, 2011 9:37 pm    Post subject: Reply with quote
Nobody? Crying or Very sad


PostPosted: Tue Oct 25, 2011 12:04 am    Post subject: Reply with quote
Are you sure that you have reassembled the lens with the two main helicoids on the right threads ?

The aperture coupling post (blue arrow, Fig 13) can sometimes become "wobbly" and this can cause problems. Tightening the screw fixes it.


PostPosted: Tue Oct 25, 2011 12:17 am    Post subject: Reply with quote
ChromaticAberration wrote:
Nobody? Crying or Very sad

I'm sorry, I've never worked on this particular lens, but other CZJ lenses can be very fiddly to reassemble and take a lot of patience sometimes so I expect this is the same. One thing I found critical is to refit the mount end correctly, with the aperture dial and the blades at corresponding positions, the A-M switch on auto and the pin actuator rocker in the right position. Even a slight amount of rotation of the mount out of position will cause the kind of problems you describe, so leave the screws a little loose until you have it working OK.


PostPosted: Tue Oct 25, 2011 12:32 am    Post subject: Reply with quote
sichko wrote:
Are you sure that you have reassembled the lens with the two main helicoids on the right threads ?


John might be right.
If me memory serves me well ( I take lecithin each morning to prevent any possible loss Very Happy) there are 27 entry points. Only one gives you the infinity. The other ones will get you, more or less, the symptoms that you already encountered.


PostPosted: Tue Oct 25, 2011 10:08 pm    Post subject: Reply with quote
Now that you guys mentioned it I actually have no idea because I have not even put that into thought, I was not aware of that detail at all. I just screw it where it fits and sometimes it takes lots of time to get it to screw in.. can it be that there is only one position anyway? Meaning that the other 26 will not screw at all?


PostPosted: Tue Oct 25, 2011 10:16 pm    Post subject: Reply with quote
ChromaticAberration wrote:
Now that you guys mentioned it I actually have no idea because I have not even put that into thought, I was not aware of that detail at all. I just screw it where it fits and sometimes it takes lots of time to get it to screw in.. can it be that there is only one position anyway? Meaning that the other 26 will not screw at all?


Sorry, but there are quite a few ways of putting the helicoids together - and only one of them is correct !


PostPosted: Tue Oct 25, 2011 10:51 pm    Post subject: Reply with quote
The rear element of the lens is proteced by a flared tube - effectively a hood. IIRC when the lens is assembled correctly, and the focus is set to infinity, the back of this hood sits just inside (by ~ 1mm) the rear of the lens mount. So you have some means of knowing when the assembly is correct. The following procedure might help in assembly.

Set the focus to infinity and make sure it stays there - tape if necessary. Providing the two helicoids are not damaged they should engage quite easily. When you manage to engage them, screw the optical unit into the focusing barrel until the slots which engage the guide rods are opposite the two pairs of holes which hold the guide rods. There's no need to attach the guide rods yet. Holding the two parts so that they don't move, relative to each other, replace the mount and check the position of the hood relative to the mount. If it's OK, remove the mount, fix the guide rods .... If it's not OK you will have to try again - systematically (mark the position of the first attempt) or otherwise.

Ideally, if you have access to another lens you could take it apart CAREFULLY noting the position of disengagement of the two helicoids. Unfortunately I don't have one at the moment otherwise I would provide detailed pictures.
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