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Middle Age Man
member
Reged: 07/12/07
Posts: 38
Loc: Northern NJ
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Hi, all. Two issues:
1. My Dec drive on my LXD75 will only operate at full speed. Even with the slew rate set to guide, 2x, 8x, 64x, etc. the dec motor will only run at the maximum speed. I cannot find a setting in the Setup -> Telescope menu that makes a difference. The RA drive runs at the proper speeds that the controller is set for. Does anyone know how to fix this dec motor problem short of sending it in to Meade? I'm running firmware version 43Eg on the #497 hand controller.
2. I've just spent all of my free time from the last week pulling apart the LXD75 in an effort to repair and re-grease it. I followed the instructions as documented on Astronomy Boy's website and pulled the whole Dec assembly apart. I began putting it back together today and I am having a very difficult time getting the large bearing back into the housing. The ball bearing is a sealed unit of type 6811Z. I cleaned the housing and did the appropriate smoothing of the inside of the cast housing, and even after re-greasing the housing the bearing did not fit back in place properly. I then attempted to put the bearing in the freezer for a few minutes and heating the housing up, hoping that the size difference from the thermal changes would allow the bearing to slip into place and when the housing cools that it tightens around the bearing, but that only allowed me to get one side of the bearing seated all of the way while the other side is half in and now stuck. The bearing seems to absorb the heat quickly and expands in a very short time frame.
I do not have a multiple-ton press that I can use to press it in place, and right now I cannot move forward with the reconstruction until the bearing is seated properly. Any ideas?
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Hardin 10" DSH
Celestron C-8
Celestron Nextar 8 GPS
William Optics 66SD
Meade 2080
Meade LXD-75
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bardo
member
Reged: 09/13/09
Posts: 54
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you could try to get a piece of PVC tubing or metal tubing that fits around the outer rim of the bearing and use it as a punch with a hammer. obviously making sure its only touching the outer metal edge so as not to tear up the bearing itself.
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rmollise
Post Laureate
Reged: 07/06/07
Posts: 4598
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Quote:
Hi, all. Two issues:
1. My Dec drive on my LXD75 will only operate at full speed. Even with the slew rate set to guide, 2x, 8x, 64x, etc. the dec motor will only run at the maximum speed. I cannot find a setting in the Setup -> Telescope menu that makes a difference. The RA drive runs at the proper speeds that the controller is set for. Does anyone know how to fix this dec motor problem short of sending it in to Meade? I'm running firmware version 43Eg on the #497 hand controller.
This can be caused by any number of things, but most often it's the little encoder wheels or the LEDs associated with them. These encoders are very easily damaged.
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Uncle Rod
Rod's New Book:
Choosing and Using a New CAT
Available now!
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codemonkey
super member
Reged: 09/16/08
Posts: 163
Loc: Lafayette, CO
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You're on the right track with the freezer, but you need to give it more than a few minutes - a good half hour or hour will do it. I needed to use the freezer but no heat when I did a rebuild on my LXD75. No real force was needed.
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AlanT
sage
Reged: 08/20/07
Posts: 488
Loc: 122º36' W, 47º37' N, WA USA
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The bearing is stuck cocked in the bore?? Ouch!
If the bearing is still stuck in the housing, freezing the assembly won't help, it will make it worse. Aluminum changes more than steel with temperature. I suppose you could warm the assy but I wouldn't at this point (You'd have to get it pretty warm to get enough change, there's the bearing grease to consider, and a bunch of unknowns in the aluminum casting).
If you didn't use a lot of force on it to this point it still may be ok. It would be best if you could straighten the bearing out by pushing the "seated" side back out, but I don't think you can see (get to) the outer race of the bearing from the under side, but if you can....
I've had the bearing jam/*BLEEP* when assembling my CG-5, but it's never been stuck hard. I've always been able to free it up with some very light raps on the outer bearing race using a wood dowel and tap hammer. Hopefully that will do it for you too.
Be careful, and good luck,
al
Edit: *BLEEP* = Become slanted, skewed, listed, inclined, or sloped resulting in the thing being stuck 
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al
Meade 80mm APO
Celestron 6" SCT
CGE, GM-8, & CG-5 GT
ST-2000xcm, DSI Pro II, DSI Pro
( www.alberts-astro.com/astro )
Edited by AlanT (10/24/09 12:14 PM)
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