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Help: Altitude bearing knobs need fixing

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4 replies to this topic

#1 nakshatra7

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Posted 03 May 2021 - 07:48 AM

Hi CN members,

 

I got my first scope, an 8' GSO Dob after waiting for it about two months.

 

I have been able to assemble it, but have come unstuck at the altitude bearing set-up. My knobs keep coming off the shafts, and even when fixed as best as I can, the optical tube doesn't fit snugly or easily into its U-shaped slots in the base.

 

I had to open the knobs, because the knurled knob wasn't working well. Inside was a ball bearing between two washers and a plastic ring. I have fixed it so the plastic ring is first on the knob, such that the screw of the black knurled knob presses on it to create tension. The washers and bearings are behind.

 

I can't understand how the knob is supposed to hold on to the shaft and provide differential tension to the tube. In the photos I have attached, you will see that the knob comes off after applying pulling it with little pressure. I am sure that shouldn't happen, and as I said, it's not fitting into the slots easily.

 

Can you please help? How do I assemble the knob and / or the altitude tension systme into the tube? Here is a link for the scope is https://tejraj.com/g...-telescope.html . I have also attached some imperfect photos; I do not want to open the knob again until I know what I am doing.

 

Thank you!

 

Attached Thumbnails

  • Knob1.jpg
  • Knob 2.jpg
  • Knob 3.jpg


#2 Tangerman

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Posted 03 May 2021 - 07:58 AM

Did you buy this new? If so, a warranty should cover this, provided you purchased it through a reputable dealer. I'd contact the dealer for some replacement altitude bearings. I've never had mine on my 10" come off. Although it's possible those black knobs just unscrewed all the way, and you can screw it back on. The black knobs are meant to screw while the metal part stays still. So I guess I'd try screwing it back on, then contact your dealer. 



#3 FlyingV74

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Posted 03 May 2021 - 07:50 PM

On my 8” Zhumell, there are tiny set screws in the black tensioning knobs. These set screws prevent the tensioning knobs from backing out all the way. Saying that, if the they are backing out, that tells you that there is friction in the mechanism that is causing this. On my Z8, I cleaned the bearings and the plastic pieces and all mating surfaces (they were sticky). Then I lubed all of these surfaces with some light weight grease (stuff that I use for my fishing reels). After doing this, I have to tighten the tension knobs as tight as I can to get enough tension to keep the tube from drooping. I prefer it this way as opposed to the way that it came from the factory. It moves much more smoothly when using higher power.

#4 Ulmer Spatz

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Posted 04 May 2021 - 05:59 AM

Did you buy this new? If so, a warranty should cover this, provided you purchased it through a reputable dealer. 

I also suggest to contact a reputable dealer, but only to ask for assembly help. It's possible that there's nothing wrong with the altitude knobs at all, but that the instructions that came with the scope are misleading or even useless. I would not mention the fact that you opened the knobs and reassembled them by guesswork. Opening these knobs is one of the things that could void a warranty.


Edited by Ulmer Spatz, 04 May 2021 - 12:19 PM.


#5 nakshatra7

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Posted 07 May 2021 - 05:04 AM

Thank you, all. I was able to assemble it back in shape, and am now just waiting for the weather to clear.  




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