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Help repairing focuser

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#1 ftwskies

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Posted 05 August 2016 - 03:50 PM

Anybody have any experience with these?

bino-levenhuk-bino-plus-12x50-dop7.jpg

https://www.levenhuk...lus-12x50/#more

 

I have an identical (and I do mean identical -- sans the levenhuk logo) pair.  Had 'em for maybe ten years or so.  The Levenhuk website says they were made in PRC, "controlled by Levenhuk", but that the model is discontinued.

 

Anyways, they've been great little DSO scouts for me for years, but I'm having trouble repairing the focuser on 'em.  Notice how the focus knob is between the arms, instead of behind 'em?  Yeah -- makes it so that you have to completely disassemble the things to get the focuser mechanism out.  Instead of a simple threaded arrangement, that big knob contains some sort of slip tube with a slot in it, and a shaft that has a screw sticking out one side that rides in a slot in the slip tube...  I guess I'll have to post some pictures to clarify what I mean.  Anywho, I recently picked up the binos to use 'em and discovered that the focus mechanism was loose.  I don't mean the knob turned too easily, I mean the eyepieces would slide in and out some without the focus mechanism turning at all.  Makes it so you can't hold focus when you put the binos up to your eyes.  They don't slide all the way, just enough free play to de-focus the image.  And they still respond to actual knob turn as well.  So I dug into 'em to see if I could figure out how to fix 'em.  Of course the entire mechanism was chock full of The People's GreaseTM -- which gets even oozier, stickier and nastier that usual in 100°+ Texas heat, lemme tell ya.  :ranting:  For now, all the parts are soaking in a Tupperware full of soapy water, but I'm sure I'll need to dig out the VOC solvents to really clean the stuff to where I can sort out the problem. 

 

The thing is, all of the repair videos I've been able to find on YouTube show how to repair standard style binos with a threaded focuser on the rear, not this kind.  I sure could use some help if anybody has experience with this sort of mechanism.  (I'll see if I can get some photos posted this weekend.  I'll probably need to get the parts cleaned up first, otherwise all you'll be able to see is goo.)


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#2 MartinPond

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Posted 07 August 2016 - 06:57 AM

Screw rides a slot in a 'slip-tube'......hmm..

A spiral track, right?

 

OK...it looks like it's the same mechanism

as the "insta-focus" or "Zip" focusers.

 

First:

    The focuser arma are usually 'press-fit' onto the center shaft together,

   so they pull out together, as a "T" shaped assembly, after you unscrew that

 groove-riding screw.   The 'press-fitted T-bar' assembly assures there is very

  little see-saw action of the eyepieces, which would mess up the field of view.

 

But.....

Second:

You cannot get rid of the in-out 'slush' you experience with thicker grease.

Ideally, you could get a bushing around that guide screw that is a little bit wider,

but the chances of that are slim, unless you have a little lathe at home.

 

So:

Some practical strategies (tested on a nice Tasco Zip with the identical issue):

1) use eyebrows to push in on the eyepieces while you focus.

   The slop will go away, but you will have to keeping bearing down..

2) use a rubber band to keep pressing forarward on an arm..

    ....you don't worry about seesaw: the press-fit scheme takes care of that

3) Take a pointer finger from one hand and press lightly on a focuser arm while

    you focus.

 

#3) Seems like the easiest and most precise method....it doesn't take much

     pressure at all to fix the 'thunking', and your finger is a lot easier to adjust than

    a rubber band.  With 2 sets of fingers on the bins/fast-focus, it's easy to have

   one stray finger nudging a little on an arm.

 

That should make life a lot easier!

Just in case...try screwing that groove-rider screw in...it may have gotten loose.

 

 

Fast focusers are ideal for moving animals less than 100 ft away,

  but for night skies I love independent focus.  Once set, always ready (save for an

  occasional tweek).

 

Still, if fast focus is what you have, that should help a lot (the pressing finger).

Note: fast focus on a 12x50 is a bit silly...


Edited by MartinPond, 07 August 2016 - 07:01 AM.

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#3 ftwskies

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Posted 08 August 2016 - 09:49 AM

Okay, I think I figured out the problem.  After getting all the parts reasonably de-gooped, I spotted a small brass screw -- odd shaped, almost like a tiny bullet -- lying sideways in the spiral track inside the main knob.  Some more fiddling and cleaning revealed that this screw had come loose from its intended position; it's supposed to be threaded into a hole at the tip of the main black plastic shaft.  The head of this screw is what's supposed to ride inside the spiral track inside the knob.  It gets inserted through a tiny hole in the side of the knob, through a window in the slip tube, through the oblong hole in the aluminum tube, and into the hole at the end of the center shaft.

 

The real trick to finishing the repair is going to be putting the whole thing back together like a puzzle.  :hmm:  It's clear where everything is supposed to go and how it all mates together conceptually, but it all has to be assembled in place, including the rubber sleeve that slips over the main knob, in the right order, and working in the tight ventral area between the two sides of the bino.  Oh, and I need to find a way to replace the viscosity of the goop (kilopoise damping grease) as I do it, without making reassembly of small bits in a tight spot with my big fat paws more difficult than it already is.  All to save a $50 bino -- such is the tenacity of my inner engineer coupled with my sentimental side.  :crazy:  Really good optics, though, so...    I'll edit this post in a bit to add the photos I took this weekend -- then all shall be made clear (including how screwed I am).   :ohmy:

 

EDIT:  Okay, here are the annotated pics...

 

gallery_240021_6385_24036.jpg

 

gallery_240021_6385_77258.jpg

gallery_240021_6385_1981.jpg

 

gallery_240021_6385_38428.jpg


Edited by ftwskies, 08 August 2016 - 10:34 AM.

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#4 MartinPond

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Posted 08 August 2016 - 12:36 PM

Ah.....I see!..

That's a new one on me.

Interesting....in between the slow-ride and the "Insta-Focus".

 

It has that screw-head-drag scheme though, like the wobblers.

 

Silicone bulb grease might by slightly thin for the job, but it's awesome

at cold temps (no change!), and you can buy it in reasonable quantity/price at the hardware store.

 

It looks much more solid than I thought   (when I thought it was an old rapid-focus track).


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#5 ftwskies

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Posted 08 August 2016 - 12:52 PM

Yeah, I plan to try using some bearing grease.  It won't be as sticky as the kilopoise, but I don't mind a little less stiffness if it holds up well at higher temps.  The triple-digit heat we get here in Tejas actually had the kilopoise kind of oozing out the crevices a bit on these even before I tried disassembly.

 

You were right, though, Martin -- it was a screw loose!  ('Course, somes that know me been tellin' me that was my problem for a while now...  ;) )


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#6 MartinPond

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Posted 08 August 2016 - 01:17 PM

That issue echoes in the little 8x21s and some 10x25s, too...

the screw-peg  that sticks into the objective 'carriage' and gets pusshed by that

'sled' thing on the hinge.    Anytime you push a lot on a side-stick it cal get

worked loose..



#7 ftwskies

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Posted 09 August 2016 - 09:37 PM

I DID IT!!  :shocked:  :cool:

 

I managed to get it all back together!  It actually wasn't as bad as I thought it would be. The rubber sleeve was more flexible than I expected and I was able to hold it back with one hand using needle-nose pliers while my other hand installed the screw. 

 

Works pretty good now. The only thing that I'm not happy about is that I replaced the kilopoise with bearing grease and while it's a heavy grease, it's very slick and waxy, and frankly not viscous at all. As a result the feel of the focuser is a lot looser and even a little skippy feeling. Still focuses accurately and holds focus though. Now that I know how to disassemble and reassemble them I think I'll try to find kilopoise in small quantities and redo it to get the nice viscous feel back. 

 

But hey -- they work and I gotta say I'm darned proud of myself.  :waytogo:

 

 


Edited by ftwskies, 09 August 2016 - 09:40 PM.

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#8 tomykay12

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Posted 14 August 2016 - 10:54 PM

Good job; you made the equivalent of about 5 bux an hour,lol. I just did kinda the same with an old pair of rugged exposure 7x50s, several hours on a 20.00 pair of binocs. it was a learning experience though. The diopter focus on these is at the objective end, right side, an unusual setup I think. IDK much about these, as they were a gift many years ago. They are working again, for now, but the mechanism is weak.


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#9 ftwskies

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Posted 15 August 2016 - 01:07 PM

Anybody got a good source for kilopoise in small quantities?

 

Anybody know if this stuff is the same/similar to kilopoise?

http://www.rcmart.co...?cPath=1555_124


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#10 slsisodiya

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Posted 14 January 2018 - 01:43 PM

I am also facing same issue , I could manage to open till particular level. could not open aluminium tube , Pls suggest  how to open this aluminium tube

 

 

 


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#11 ftwskies

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Posted 18 January 2018 - 05:51 PM

sls --

 

Sorry, I just saw your post.  It's been a long time since I did this; let me pull these binos back out and see if I can remember the step-by-step on how to take down the whole assembly.  (I've been meaning to replace the axle grease I used with something more viscous anyway, so it won't hurt to spend the time taking it back apart.)  I'll post it here when I can get some time to mess with it...  maybe this weekend...


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#12 slsisodiya

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Posted 19 January 2018 - 12:55 PM

ftwskies

 

----------------------------------------------

Thanks , Waiting for your suggestion

.



#13 Bob4BVM

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Posted 19 March 2019 - 12:36 AM

bump

 



#14 dara_t

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Posted 11 April 2021 - 06:54 AM

sls --

 

Sorry, I just saw your post.  It's been a long time since I did this; let me pull these binos back out and see if I can remember the step-by-step on how to take down the whole assembly.  (I've been meaning to replace the axle grease I used with something more viscous anyway, so it won't hurt to spend the time taking it back apart.)  I'll post it here when I can get some time to mess with it...  maybe this weekend...

facing the same issue as well as slsisodiya
wondering if that "weekend" has came yet or not...wink.gif



#15 Ant1

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Posted 11 April 2021 - 10:40 AM

Sorry, not sure what your problem is, "could not open aluminium tube" doesn't make sense to me. Could you be more specific, a picture or two can help as well.

Regards,

Ant1




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