Celestron AVX Servicing

[Thalestris24]

Hi

I know it's a bit of a quiet time but was wondering if there's anyone about who might know where I might find info about stripping down and servicing an AVX? I've not been able to find anything via Google but feel there must be something, somewhere!

Thanks

Louise

[iapa]

I'll be watching this thread with interest as mine is back for 2nd repair, and the 2yr warranty is up in a few months.

[PeterCPC]

I too would be interested. I managed a bit of regreasing but I could not find any info either.

Peter

[Thalestris24]

3 hours ago, PeterCPC said:

I too would be interested. I managed a bit of regreasing but I could not find any info either.

Peter

Yeah, would be nice to have an Astrobaby-style guide. I suppose the avx will be similar-ish... I have a lot of backlash on mine on both axes. I've adjusted the motor gears but it hasn't really helped. Not sure what other adjustments are available. I suppose I could just undo it and see. I also get a lot of stiction in both axes - not sure how much it's characteristic of the mount.

Louise

[PeterCPC]

I get a lot of stiction as well - I don't think you can do much about that. I found that the original grease had migrated away from the cog wheels so they were quite dry in the teeth. I managed to put some new grease in but I found that one of the motor covers could not be removed without removing the panel where you plug everything in so I just did what I could through a small gap as I did not want to remove the housing without some instructions. It would be nice to find an exploded view of the mount at least.

Peter

Edited May 26, 2016 by PeterCPC

[Thalestris24]

49 minutes ago, PeterCPC said:

I get a lot of stiction as well - I don't think you can do much about that. I found that the original grease had migrated away from the cog wheels so they were quite dry in the teeth. I managed to put some new grease in but I found that one of the motor covers could not be removed without removing the panel where you plug everything in so I just did what I could through a small gap as I did not want to remove the housing without some instructions. It would be nice to find an exploded view of the mount at least.

Peter

Hi

I managed to remove the covers ok though I think it was a little awkward. I seem to remember one of the screws was difficult to access but could just about manage it with some rotation of the axis. There is a 'side mounted' screw just above the latitude scale which obviously has to be undone in order to properly remove the RA motor cover. There was a clear, sticky grease on the cogs but I don't think it's the cause of any problems. I adjusted the motors to minimize backlash but it's still there  I have a suspicion that the problem could be elsewhere. It's hard to judge balance and east heaviness with all the stiction! Apart from that I really like the mount. I might be brave and try and undo it all...

Louise

[iapa]

I remember seeing a Youtube video of someone correcting backlash on the AVX - it you haven't already seen it.

Celestron Advanced VX gearbox adjustment

Edited May 26, 2016 by iapa

[iapa]

Extract from a thread on CN. (http://www.cloudynights.com/topic/489346-celestron-avx-ra-axis-issue/)

Under the RA covers are two spur gears.  The top one is attached to the worm gear drive shaft.  The bottom is attached to the drive motor.  If these spur gears are meshed to tightly they will cause the motor to speed up and slow down at tracking speed due to binding.  So I would check that first.  With the covers off in a quiet room you can hear it speed up and down and the motor start to labor when the mount is tracking.   There are three motor adjustment bolts to allow you to move the motor in and out to adjust the spur tightness..

 

Second... even if the spur gears are not binding your RA could still be speeding up and down, or even stalling and this could be a result of your top spur/worm gear engagement to the RA drive ring.  If you look up and behind the motor you will see two socket head screws and a small recessed allen head screw in the middle.  The allen head screw is a standoff screw that adjusts the housing depth holding the worm gear drive shaft.  If the worm gear drive shaft is held too tightly or is not level to the RA drive ring it can periodically stall the motor.  Or speed it up and down from the resistance, leading to bad tracking.   If it is too loose you will get a knock and bad tracking as well due to the gears skipping..  There is a fine balance to getting it just right.  I adjusted the middle recessed allen head screw to get things just right and then just barely snugged the two socket head screws.  Barely snugged means tightened them to just touch and no more..  The two socket head screws play off the middle allen to adjust depth.

[Thalestris24]

12 minutes ago, iapa said:

Extract from a thread on CN. (http://www.cloudynights.com/topic/489346-celestron-avx-ra-axis-issue/)

Under the RA covers are two spur gears.  The top one is attached to the worm gear drive shaft.  The bottom is attached to the drive motor.  If these spur gears are meshed to tightly they will cause the motor to speed up and slow down at tracking speed due to binding.  So I would check that first.  With the covers off in a quiet room you can hear it speed up and down and the motor start to labor when the mount is tracking.   There are three motor adjustment bolts to allow you to move the motor in and out to adjust the spur tightness..

 

Second... even if the spur gears are not binding your RA could still be speeding up and down, or even stalling and this could be a result of your top spur/worm gear engagement to the RA drive ring.  If you look up and behind the motor you will see two socket head screws and a small recessed allen head screw in the middle.  The allen head screw is a standoff screw that adjusts the housing depth holding the worm gear drive shaft.  If the worm gear drive shaft is held too tightly or is not level to the RA drive ring it can periodically stall the motor.  Or speed it up and down from the resistance, leading to bad tracking.   If it is too loose you will get a knock and bad tracking as well due to the gears skipping..  There is a fine balance to getting it just right.  I adjusted the middle recessed allen head screw to get things just right and then just barely snugged the two socket head screws.  Barely snugged means tightened them to just touch and no more..  The two socket head screws play off the middle allen to adjust depth.

Thanks! Some interesting stuff there which I'll look into.

[PeterCPC]

30 minutes ago, Thalestris24 said:

Hi

I managed to remove the covers ok though I think it was a little awkward. I seem to remember one of the screws was difficult to access but could just about manage it with some rotation of the axis. There is a 'side mounted' screw just above the latitude scale which obviously has to be undone in order to properly remove the RA motor cover. There was a clear, sticky grease on the cogs but I don't think it's the cause of any problems. I adjusted the motors to minimize backlash but it's still there  I have a suspicion that the problem could be elsewhere. It's hard to judge balance and east heaviness with all the stiction! Apart from that I really like the mount. I might be brave and try and undo it all...

Louise

Louise

Thanks for that. I am not brave enough to strip it down but I would love to know how you get on if you do. I am getting good guiding generally, even with the stiction, so am I loath to interfere too much. Some dodgy guiding I had was down to dithering so be aware of that. There is more on the BYE forum.

Peter

[iapa]

I've been skimming the hinterweb over lunch and one thing that I've seen a couple of times is that the AVX is a difficult mount to work on.

 

[PeterCPC]

That's because there are no instructions I expect

Peter

[Thalestris24]

1 hour ago, PeterCPC said:

Louise

Thanks for that. I am not brave enough to strip it down but I would love to know how you get on if you do. I am getting good guiding generally, even with the stiction, so am I loath to interfere too much. Some dodgy guiding I had was down to dithering so be aware of that. There is more on the BYE forum.

Peter

Mine is +/-4" but I think a lot of that is due to seeing (even with 2s or greater guide exposures) and maybe also (mostly?) to thermals. I might have some dynamic balance issues as I've been imaging with a cooled 550d (the cooling fan/heatsink on the left of the camera body is quite heavy and probably causes an imbalance), 200mm lens and 150mm guidescope. The guidescope sits atop the 550d+lens in a kindof piggy back mounting arrangement. I'm waiting for an item so I can modify the setup so I won't go poking around in the avx before I've sorted that. I could do with some sort of set of small weights to help me balance it properly. In principal, imaging/guiding at a mere 200mm should by a cinch but it actually isn't!

Louise

 

[iapa]

@Thalestris24 Thing is, you can get something like this single 60s unguided image with an 8" reflector on the AVX.

@PeterCPC One of the site i looked as was Dark Frame Optics http://www.darkframeoptics.com/page/tuning in Hampshire who say they do tuning on their own mounts then will do yours based on their experience, as against Deep Space Products who will sell you a kit to do it yourself - with DVD instructions.

I'd like to get my hands on a copy of that DVD - without spending the $400 for the kit.

 

[iapa]

I think I have something to try - when the AVX is out of warranty.

There a detailed list of steps for cleaning down an AVX.

Worm Gear Upgrade for Lower Periodic Error

https://ca.groups.yahoo.com/neo/groups/celestronVX/conversations/topics/1607

Given it's a bank holiday weekend, I may settle down to looking for more info a a more systematic way.

[Thalestris24]

18 hours ago, iapa said:

@Thalestris24 Thing is, you can get something like this single 60s unguided image with an 8" reflector on the AVX.

@PeterCPC One of the site i looked as was Dark Frame Optics http://www.darkframeoptics.com/page/tuning in Hampshire who say they do tuning on their own mounts then will do yours based on their experience, as against Deep Space Products who will sell you a kit to do it yourself - with DVD instructions.

I'd like to get my hands on a copy of that DVD - without spending the $400 for the kit.

 

Hi

Yeah, I've had 2min unguided subs @400mm before but I know my current setup has balance problems. I've ordered some weights which I hope will facilitate balancing the camera :). Maybe the mount itself is fine...

Louise

[HighlandBoy]

8 hours ago, Thalestris24 said:

One of the site i looked as was Dark Frame Optics http://www.darkframeoptics.com/page/tuning in Hampshire who say they do tuning on their own mounts then will do yours based on their experience, as against Deep Space Products who will sell you a kit to do it yourself - with DVD instructions.

I am also interested in trying to reduce stiction in my AVX mount. I had a look at the above link and unfortunately this is what they say " the AVX mount is off limits at present, and is notoriously difficult to work on. "

[mwayne]

Hi Louise,

I found this a while back, after the warranty on my AVX expires I'm taking mine apart and using a different kind of grease when putting it back together.

https://m.flickr.com/#/photos/10605262@N04/sets/72157646742806679/_QM_ytcheck_IS_1

[Thalestris24]

20 minutes ago, mwayne said:

Hi Louise,

I found this a while back, after the warranty on my AVX expires I'm taking mine apart and using a different kind of grease when putting it back together.

https://m.flickr.com/#/photos/10605262@N04/sets/72157646742806679/_QM_ytcheck_IS_1

Hi

Some of that looks useful  Some more text to go with it would be good but at least there are some useful pics. The one with the worm gear adjustment screws is useful

Thanks

Louise

Edited May 27, 2016 by Thalestris24
added text

[mwayne]

3 minutes ago, Thalestris24 said:

Hi

Some of that looks useful  Some text to go with it would be good but at least there are some useful pics.

Thanks

Louise

If you click on the individual pics each one has some text.

[Thalestris24]

Just now, mwayne said:

If you click on the individual pics each one has some text.

Yeah I realised that and updated my post!

[mwayne]

On 5/27/2016 at 17:54, Thalestris24 said:

Hi

Some of that looks useful  Some more text to go with it would be good but at least there are some useful pics. The one with the worm gear adjustment screws is useful

Thanks

Louise

There's this on the AVX:

https://ca.groups.yahoo.com/neo/groups/celestronVX/conversations/messages/1621

[Thalestris24]

2 hours ago, mwayne said:

There's this on the AVX:

https://ca.groups.yahoo.com/neo/groups/celestronVX/conversations/messages/1621

Ooh that looks very useful - especially combined with the Flickr photos from above

Mines been not too bad tonight but the PHD2 calibration is still a bit iffy - seems to struggle with the clearing backlash step. Drift align PA is good. As we're coming up to longest day it's a good time to take the plunge and strip it down. I'm still under warranty but needs must!

Thanks very much!

Louise

[mwayne]

12 hours ago, Thalestris24 said:

Ooh that looks very useful - especially combined with the Flickr photos from above

Mines been not too bad tonight but the PHD2 calibration is still a bit iffy - seems to struggle with the clearing backlash step. Drift align PA is good. As we're coming up to longest day it's a good time to take the plunge and strip it down. I'm still under warranty but needs must!

Thanks very much!

Louise

You're welcome, glad to help out. After finishing, you'll be the AVX expert here on SGL and can advise me when I work on mine ; )

[iapa]

20 hours ago, mwayne said:

There's this on the AVX:

https://ca.groups.yahoo.com/neo/groups/celestronVX/conversations/messages/1621

Part of the thread I posted a link to t'other day 

LOL

 

It's in my 'book of fixing stuff' which I may publish sometime next century