Disassemble CY 35-70 3.4?

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Archive 2012 · Disassemble CY 35-70 3.4?

jotdeh
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p.1 #1 · Disassemble CY 35-70 3.4?

Hi!

I missed my 35-70 quite a bit so I got an almost new one... which I dropped within a matter of days.

It's hard to believe, but it looks like I was lucky enough and overall the IQ has not suffered. However, focussing is very stiff now - the focus barrel rubs against the zoom barrel at the dent.
So my plan is to remove the focus barrel, file away some of the material and reassemble.
Exactly how do I take the lens apart, as little as required? I don't want to end up with an impossible puzzle of parts...

Thanks!

Johann

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Mar 29, 2012 at 09:36 PM

mco_970
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p.1 #2 · Disassemble CY 35-70 3.4?

Ooooh, bummer. Sorry about that. Seems like Jae (Flypenfly) has a CY35-70 that he needs to assemble. Maybe you guys can work together - and post some pics for those of us who might need them in the future.

Mar 29, 2012 at 10:01 PM

jotdeh
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p.1 #3 · Disassemble CY 35-70 3.4?

Yes, I'm really annoyed with this... I should never buy "new" lenses anyway, as it keeps me from using them. But the dent is like the first stain of tomato sauce on a new shirt. After it's happened I can enjoy the rest of the meal much better

Mar 29, 2012 at 10:17 PM

jcolwell
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p.1 #4 · Disassemble CY 35-70 3.4?

A few months ago, I took photos and wrote up a description to sell my CZ 35-70/3.4 it on the auction site. It has a jaggedy mark on its front element coating. Not a scratch, a mark. Then I recanted. It still takes great photos, yet its resale value is compromised.

Have you considered sliding a small, flat-bladed screwdriver in, and carefully wiggling, torquing, and/or prying it - just a bit? You could even put a layer of some thin yet resilient polymer sheet under the driver bit, to protect the lens barrel beneath.

OTOH, taking it apart could be a most-excellent adventure. Please, keep us posted.

Mar 30, 2012 at 12:24 AM

jotdeh
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p.1 #5 · Disassemble CY 35-70 3.4?

Jim, yes, that's my experience too - if an item is not mint looking enough to fetch the price the IQ would warrant, it's best kept as a 'user'.
I had tried to use a screwdrive before, but didn't feel comfortable with it. Now I used some 240 grit sandpaper, slid in inbetween the gap and rotated the focus barrel. It's still stiffer than I'd like, but definitely usable!

Mar 30, 2012 at 01:43 PM

AhamB
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p.1 #6 · Disassemble CY 35-70 3.4?

I think sandpaper isn't a great idea because you'll probably get grains from the sandpaper and/or metal particles from the zoom/focus ring in the focusing helicoid or other parts of the mechanism (or between the optics).

Mar 30, 2012 at 01:52 PM

jotdeh
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p.1 #7 · Disassemble CY 35-70 3.4?

Yes I was afraid of that as well, it creates very fine dust. I tried my best working very slowly, holding the lens with the opening to the bottom to let the dust fall out.
Maybe wetting the sandpaper a bit is a good idea to bind the dust?

Mar 30, 2012 at 02:07 PM

Bifurcator
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p.1 #8 · Disassemble CY 35-70 3.4?

it LOOKS like you do NOT need to disassemble it. And fileing on that surface would be a huge mistake.

Instead try to reform the circularity by putting it in a rubber jawed vice and squeezing it on it's (now) long diameter. Monitor the gaps on the sides so you don't squeeze the inner barrel, and squeeze it one neat the section with the ding, and you should be OK.

I dunno... that sounds so much better than using a file (or sandpaper!!) on it.

Edited on Mar 30, 2012 at 02:53 PM · View previous versions

Mar 30, 2012 at 02:38 PM

jotdeh
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p.1 #9 · Disassemble CY 35-70 3.4?

I think the problem is that such small deformation (fraction of a mm compared to 60 mm barrel) it will just spring back. Still worth a try, thanks Bif!

Mar 30, 2012 at 02:46 PM

Bifurcator
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p.1 #10 · Disassemble CY 35-70 3.4?

Well, you're looking at it so you know best. If it's a dimple, dent, or small depression then my idea will only help a little bit (enough? you can probably guess yourself by looking at it). If the deformation is more of a gentle slope it should work the treat tho. In the image it looks like a gentle enough slope that it should work. While in the vice under some pressure and if that alone doesn't do the trick then I would tap on it at the same time with a rubber mallet - gently but enough.

If neither way worked then disassemble it and use some soft wood and a hammer/mallet to pound out the dent. That would actually be the most professional way to go about it - but also the most work too. :-/

Mar 30, 2012 at 03:00 PM

jotdeh
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p.1 #11 · Disassemble CY 35-70 3.4?

Well you are right, the oval shape is very slight, and as long as I focus holding the lens in two points then the focus is pretty smooth! I need to get myself access to a vice and see what I can do with that - sounds a bit scary though

Mar 30, 2012 at 11:56 PM

jotdeh
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p.1 #12 · Disassemble CY 35-70 3.4?

Just a quick update - I've finally dared to take the lens apart (three components - front assembly, focussing cylinder and rear assembly). First thing I tried again was to sand away the bump on the inside caused by the dent. It didn't solve the focussing issue (still way too stiff, depending where I pinch the lens with two fingers).
So then I went Bif's way, though sans vice. I gently "massaged" the cylinder into shape a couple of times, and now...

well it's not a "brand-new" feeling, but definitely very useable!

I'm happy! I'll post a pic or two later for those interested.

Apr 24, 2012 at 10:24 PM

jotdeh
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p.1 #13 · Disassemble CY 35-70 3.4?

The rubber grip slides off easily if you lift it with a flat screwdriver.
You will see a total of four screws exposed immediately.

Two plain slotted with a nylon washer need a 3mm screwdriver (any smaller and it chews up the screws

Remove them and then you can unscrew the entire front assembly. Takes maybe 4 full turns or so? Be sure to set the focus to infinity, and when the front comes off, mark both parts to remember the correct alignment. The helicoid has multiple parallel threads, so if you don't get the right thread then your lens won't focus to infinity (it'll be way off, so you will notice the mistake, trust me

Now you can already clean some parts of the lens.

If, like me, you need to take the focussing cylinder out then you have to unscrew the Philips (cross) screws just a little bit. They hold a small plate the stops the lens from focussing past infinity. If you slide it upwards you can also unscrew the focussing cylinder, which takes a lot of turns! Do NOT remove the screws completely, there's no need for that.
Not sure if there are multiple threads there, but be sure to mark out the final orientation (i.e. what it looks like before disassembly).

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Apr 25, 2012 at 08:57 AM

jotdeh
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p.1 #14 · Disassemble CY 35-70 3.4?

It's really not difficult, just don't use any force when joining the threads back together again.

Apr 25, 2012 at 08:58 AM

mco_970
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p.1 #15 · Disassemble CY 35-70 3.4?

Oh wow, good job. Bookmarking this link, just in case...

Apr 25, 2012 at 01:17 PM

jotdeh
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p.1 #16 · Disassemble CY 35-70 3.4?

Thanks

If there's dust in your lens I'd give this a try without hesitation now. You might be lucky and it's on the surfaces exposed by this disassembly (not unlikely, since the zoom and focussing action is happening here). Only getting to the aperture would be a bit more adventurous.

Apr 25, 2012 at 01:32 PM

jotdeh
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p.1 #17 · Disassemble CY 35-70 3.4?

To conclude, does it really work? Click for full size image

Click for full size

Apr 30, 2012 at 12:25 AM

LocoPhoto
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p.1 #18 · Disassemble CY 35-70 3.4?

What camera did you use to take your test shot?

No offense but it doesn't look sharp to me? It looks ever so slightly off, not that crisp punch of sharpness that a Zeiss lens provides.

I'd also try shooting the side of a semi truck trailer that has graphics on it to test it for edge to edge alignment of focusing at the film plane. That dent looks like a bad place to hit a lens.

Loco

May 01, 2012 at 07:53 PM

jotdeh
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p.1 #19 · Disassemble CY 35-70 3.4?

I'd actually say there is a good amount of pop, but let's not get into that here

However I really do think (want to believe? lol!) that the lens is fine.
In fact this may have been the best spot to hit the lens. No lens elements are directly attached to the one touch barrel (let's call it that), and it could be restored just by working this part.

I'll do a more controlled "wall test" in the next few days, just to make sure. It's quite possible that the plane of focus is in ever so slightly in front (i.e. on top) of the rock at the bottom.

Camera is a 5D2.

May 01, 2012 at 10:09 PM

LocoPhoto
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p.1 #20 · Disassemble CY 35-70 3.4?

Did I mention I'm 74 and can't find my glasses?

Hope it winds up being stellar, and thanks for the info on no elements behind the impact area...that is a good thing you're right. I was thinking any impact in the barrel would blunt trauma it's way to wiggling an element, but I think these lenses are tougher than I think since they're held in place by the force of curved metal as well...the science is interesting, and typical me...not something I'm as educated on as I'd like.

Let us know how it winds up,

Loco

May 02, 2012 at 04:04 AM

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