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Vixen BT81S-A problem with finder shoe - grief

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#1 Ira

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Posted 30 November 2021 - 06:19 PM

I want to replace the finder shoe on my Vixen binos. There are two slotted screws that hold it in place. I unscrew them and they are loose but they won't detach from the tube and the finder shoe won't lift off. So I go to screw them back in but now the screws won't bite and secure the shoe. They just spin loosely.

 

Any ideas on what to do? I'll be happy getting the shoe off or getting it screwed back in.

 

Ira

 

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#2 Rich V.

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Posted 30 November 2021 - 06:27 PM

Slip a thin edged tool like a thin bladed screwdriver or knife under the bracket and gently pry it outward while re-tightening the screws.  The prying pressure outward may allow the nuts inside the tube to grab enough to catch and tighten.  You don't want them to drop off inside the OTA and rattle around.  frown.gif

 

Rich



#3 wrvond

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Posted 30 November 2021 - 06:40 PM

^^ That could work. Otherwise you're going to need to remove the focuser via the three pan head screws attaching the collar to the optical tube then reach up inside and hold the nuts with your fingers. A wrench generally isn't necessary with these.



#4 Ira

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Posted 30 November 2021 - 06:42 PM

Slip a thin edged tool like a thin bladed screwdriver or knife under the bracket and gently pry it outward while re-tightening the screws.  The prying pressure outward may allow the nuts inside the tube to grab enough to catch and tighten.  You don't want them to drop off inside the OTA and rattle around.  frown.gif

 

Rich

The screws are not in danger of falling into the tube because they are stuck on the finder shoe base. It did occur to me that the screws may have been held by internal nuts but there's nothing rattling around and it didn't feel like it when I unscrewed them. I did try pulling up on the finder shoe base with my fingers when I tried to get the screws back in, but that didn't help. Maybe more pressure is needed. Or maybe I can try prying the finder base off now that it's loose? I don't know. 



#5 wrvond

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Posted 30 November 2021 - 06:46 PM

The screws are not in danger of falling into the tube because they are stuck on the finder shoe base. It did occur to me that the screws may have been held by internal nuts but there's nothing rattling around and it didn't feel like it when I unscrewed them. I did try pulling up on the finder shoe base with my fingers when I tried to get the screws back in, but that didn't help. Maybe more pressure is needed. Or maybe I can try prying the finder base off now that it's loose? I don't know. 

If the screws do not fully unscrew from the optical tube it's because they have nuts on the inside of the tube.



#6 Ira

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Posted 30 November 2021 - 07:01 PM

Rich,

I see you meant the nuts and not the screws falling in. Applying leverage didn't help. It's seems screwy to me to use nuts and bolts here instead of a screw, like every other telescope I own.



#7 Supernova74

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Posted 30 November 2021 - 07:02 PM

I feel your pain.why don’t manufacturers tap weld a small nut inside the OTA.ive spoken to a few dealers in the the past about this simple fix or solution.however there response is manufacturing costs and time,all due respect this takes no time whatsoever as I’ve done this on many occasions and it literally takes seconds to place a couple of tap welds on the nuts.i was considering changing the dove tail on a skywatcher 180 mak several weeks back and it just seems ridiculous that you have to remove either the correcter plate end or the primary mirror.


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#8 Rich V.

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Posted 30 November 2021 - 07:10 PM

Seems "screwy" to me, too, Ira.  wink.gif

 

You might look through the objective lens with a flashlight towards the prism end of the tube and see for yourself what's on the other side of those screws.  You should see the screws poking down into the tube.  Don't try to take the turrets off; there's another prism back there under the turret.  You're opening up a can of worms, so to speak.

 

Did you ever get the turret to rotate with some heat applied?

 

Rich



#9 wrvond

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Posted 30 November 2021 - 08:43 PM

Oops! I saw the "Vixen" part but the "BT81S-A" part didn't register. shocked.gif blush.gif

As Rich says, opening the turret end is not a good idea.



#10 Ira

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Posted 01 December 2021 - 03:47 PM

Turret is still firmly stuck. Awaiting further instructions from Teleskop-Service.

#11 Ira

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Posted 02 December 2021 - 09:26 PM

Seems "screwy" to me, too, Ira.  wink.gif

 

You might look through the objective lens with a flashlight towards the prism end of the tube and see for yourself what's on the other side of those screws.  You should see the screws poking down into the tube.  Don't try to take the turrets off; there's another prism back there under the turret.  You're opening up a can of worms, so to speak.

 

Did you ever get the turret to rotate with some heat applied?

 

Rich

Good advice on looking down the tube with a flashlight. Why didn't I think of this before starting? Upon inspection, the  finder shoe is, indeed, held to the tube by two bolts secured by a flat washer and nut. Couldn't they have used a lock washer? I managed to apply enough leverage with a screw driver to lift the finder shoe so that the nuts could bite and sorted the problem. Thanks to everyone for their suggestions.

 

Now on to the stuck left turret assembly. I have not yet applied heat but that is next on the list.

 

/Ira


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#12 BUDSBOY

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Posted 02 December 2021 - 09:55 PM

If you have a magnifying glass, you could localize/focus the heat.




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