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LX90 10” RA st st stutter

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#1 Pedro724



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Posted 11 March 2021 - 01:29 PM

Hi all,

Just joined this forum - apologies - it took me a long time but found the need to ask fellow Meade owners.


my LX90 GPS 10” has developed an annoying issue. During set up the RA slew in either direction and at speeds set from HBX buttons 4,5,6 slews like the motor / scope is stuttering. I can see the image move smoothly then jump a few times then smooth. This repeats till i get centred on both stars. A few times during last clear skies here in Blighty when tracking i can see the odd ‘stutter’. The RA motor sound changes when this happens but does not make a metal to metal crunching sound.


A few years back [scope is 4 years old from new] this happened when i had the scope mounted on a Meade wedge in polar mode. It stopped when i took it off. Then a little while back in 2020 it started again in Alt/Az and i did some Peterson upgrades (focuser and Dec clutch. Whilst the scope was on the bench i took a look at the RA grea, cleaned it thoroughly and did not detect any crap in the gears. It had the right amount of Peterson red magic and then all put back.


From the last session i then googled CS forum and did drive training. The scope stutter in RA most noticeable. Dec is fine. I have the ‘latest’ HBX software [though I’m sure OzAndrew would suggest the patched firmware.


My ask is - has anyone else had this? What worked for them to fix it? Any tips please? CS forum has given me lots of tips inc the scary Encoder clean - might look at that next depending on other wise words. The latter is interesting as i had an issue with my original finder scope - this has grease all over the internal optics. Looked like the scope got how and the internal lube ran down into the optics [yep i took it all apart!]


Peter at MeadeUK [Opticstar] suggested this forum may help and my next step will be this Saturday to re train the drives putting my iPhone on the scope to video the ‘issue’.


many thanks



  • MistrBadgr and RickScofield like this

#2 MistrBadgr


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Posted 18 March 2021 - 01:44 PM

Hi Pete,


I passed your post on to Meade Customer Service, after I remembered to.  I was going to earlier, but was interrupted with something urgent and forgot until now.


Some questions that have crossed my mind:


Does the stutter if the same length each time or does it stutter longer some times and shorter others?

Does the time from the start of one occurrence to the start of another stay the same? 

Does it happen quicker at higher speeds than at lower? 

Does the pitch change at higher speeds?

Does it happen at the same spots as the scope travels around in a circle?

Is there any difference in the behavior when traveling in one direction compared to the other at any of the speeds?


If the motor seems to be slowing down only, with no vibration, I am wondering if there could be a film or something else on the contact track for the electrical brush related to the azimuth drive.  If there is something that can impede current flow to the motor on that track, it could bog the motor down, but I do not think it would be a directly repeatable behavior as the scope travels around the circle.  If the behavior is very repeatable as the scope travels around the loop, I am thinking something like a rough spot on one of the gears.  With a different behavior from one direction to another, I can see that being an indication of a rough spot on the side of one or more gear teeth, but not on the other.


Anyway, just thoughts.



Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

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