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Accidental disassembly of helicals - a cautionary tale
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PostPosted: Mon Oct 07, 2013 10:59 am    Post subject: Accidental disassembly of helicals - a cautionary tale Reply with quote

My Konica AR 28/3.5 has always had stiff focusing, with the unmistakable sound of grinding when turning the focusing ring. Sometimes, the focusing ring has "slipped" when turning (the ring moved, but not the helical), which Ive never experienced before. Last night, it slipped so badly that the helical started to unwind. The focusing ring was just "hanging" round the barrel (like a hula hoop), so I had to unscrew the helicals to get it off.

Im sure that is not the way the lens is designed to come apart, but I finally ended up with all the helicals separated (three parts all in all).

Ive always thought about trying to regrease a lens, and now I dont have any choice. Of course, there was no way for me to mark the different parts at the point of separation, so reassembly will be a challenge...

I just bought some nice, NLGI 1 grade, grease, and will try and regrease and reassemble the darn thing tonight.


PostPosted: Mon Oct 07, 2013 12:15 pm    Post subject: Reply with quote

That's a shame....but let us know how you fixed it as it could come in handy if anyone of us has the same problem.


PostPosted: Tue Oct 08, 2013 8:33 am    Post subject: Reply with quote

Ill update this thread as the work progresses. The final outcome is far from certain, so this might be a cautionary tale indeed. Anyway, here is a photo of the lens itself (ironically taken for the purpose of selling it along with two others, I just wanted to check that the focusing helicoid had not gotten worse so that my description of its condition would be accurate, and here I am...)



And here it is in its current state:


Top left is the lens "guts" (optics and aperture mechanism) which screws into the aluminium ring (bottom left) which in turn fits inside thee bottom right part, surrounded by the aperture ring (top right).

I will clean them all up and do a couple of "dry runs" without grease to see that I can manage to get it reassembled at all. If and when that works out, I will lube it up and finish the job. Stay tuned...


PostPosted: Wed Oct 09, 2013 6:37 am    Post subject: Reply with quote

Its dead. It proved too difficult to put the pieces back, with no clue about how far each section should screw into the other in order for the whole thing to come together. The aperture closing pin also got involved, opening and closing the aperture blades as the optical block spun around inside the barrel while trying to screw everything in place. Lesson learned, dont ever tamper with helicals unless youre certain you know what youre doing...


PostPosted: Wed Oct 09, 2013 8:26 am    Post subject: Reply with quote

Sorry to hear that. A mark on both pieces (I use a screwdriver blade for that) to see how they fit BEFORE taking them apart is a good idea.


PostPosted: Wed Oct 09, 2013 8:48 am    Post subject: Reply with quote

Yeah, I know. Ive even told others that, when giving advice on how to clean/lube lenses. In this case, however, the helical(s) and focusing ring unscrewed as a result of too stiff focusing, so the circumstances were less than ideal to begin with. Thank God I have a similar lens (all black 7-element 28/3.5 AR) and that the one I ruined cost me next to nothing. I'll put the cost down to "learning money".


PostPosted: Thu Oct 10, 2013 12:26 am    Post subject: Reply with quote

It is something to continue tinkering with. I've done this on several occasions and been successful. Great patience is required!

The very thing happened to me recently with my misadventures noted in another thread. The lens and I are both relaxing while I locate my pin vise to drill out a screw.

Best of luck (and skill)!


PostPosted: Mon Nov 25, 2013 8:08 pm    Post subject: Reply with quote

You need a lot of patients to assemble this. But if some of your friends have same lens you can borough just to see how much some parts go out or in to find correct place.


PostPosted: Sat Dec 07, 2013 11:51 am    Post subject: Reply with quote

Putting helicals back together is not as complicated as people make it out to be. Yes, if it came apart before you marked it it may take quite a bit of time, but it is hardly impossible. FWIW, it's likely that to put it back together you need to separate focusing assembly from the mount.


PostPosted: Sat Dec 07, 2013 1:23 pm    Post subject: Reply with quote

Gardener wrote:
Putting helicals back together is not as complicated as people make it out to be. Yes, if it came apart before you marked it it may take quite a bit of time, but it is hardly impossible. FWIW, it's likely that to put it back together you need to separate focusing assembly from the mount.


Of course, it's not impossible, someone has done it when the lens was assembled for the first time.
But the key is to know how! Wink


PostPosted: Sat Dec 07, 2013 6:14 pm    Post subject: Reply with quote

LucisPictor wrote:
But the key is to know how!


The task is not beyond a regular person. Patience, and a bit of understanding of how lenses are put together is all that required.


PostPosted: Sun Dec 08, 2013 12:50 am    Post subject: Reply with quote

I had an issue some time ago with a CZJ 3.5/135 that I bought to try to "fix" the helicoid wrong mounted, and tried out 2 days without success. The lens rested dismantled for months. One day, I waked up with an idea, and it finally worked out! It was a matter of the correct entry point (as when you come back from space) and how many turns to do, at the same time reaching infinity, close focus and the correct position of the distance marks on the barrel.

Good look, let the lens just some palce you can come back later, and I hope you'll find a solution and fix it!

Cheers,

Renato