Trying to solve slewing issue CPC800

[Chris]

I've used my CPC800 a couple of times since I bought it, both times it almost ground to a halt when slewing after a little while. I mentioned this to a past CPC1100 owner a while ago who said his did the same until he upgraded the cable, then all was well.

I've upgraded to an Astro Lynx cable and then the power supply to a Nevada 8A bench PSU and thought all would be well. To be honest I didn't hurry to check all was well as I was so convinced it was a power supply issue. It just made sense after asking around.

Well today I read a thread where a members Sky Prodigy mount was acting up when slewing anti clockwise and it turned out to be a motor issue . Alarm bells rang, was it the same issue just on azimuth anti clockwise with mine? The answer appears to be yes.

I've put this short video together demonstrating the problem. It might be slightly better with the new cable and supply in place, but sadly it still ain't right.

 

[Sunshine]

OOOH that sounds painful! its strange that its only anticlockwise, could it be a gear issue and not really a motor issue? could the gear train be misaligned somewhere and when the base reaches a certain point the gears begin to seize up slowly??

Edited August 12, 2018 by Sunshine

[Chris]

14 minutes ago, Sunshine said:

OOOH that sounds painful! its strange that its only anticlockwise, could it be a gear issue and not really a motor issue? could the great train be misaligned somewhere and when the base reaches a certain point the gears begin to seize up slowly??

It could be the gears binding a bit, I think that's why you get a little oscillation with goto mounts because gear tolerances can't be made accurate cheaply. I was just a bit alarmed when I read another members thread today who said his celestron mount did the same thing anti clockwise in azimuth and it turned out to be the motor, Celestron is sending him a relpacement motor. This is kind of understandable though as his mount is a number of years old, but mine has only been used twice since new and did this straight the way, so why would the motor have gone already? This brings us back to your point.

[RobertI]

Hi Chris, my SkyProdigy actually has the problem in the opposite (clockwise) direction to yours, although it doesn’t necessarily mean the motor is turning in a different direction. Does you problem happen at the same point on the azimuth axis, or does it exhibit the same issue wherever it is? Does it actually almost grind to a halt or just slow down? My mount didn’t exhibit the same oscillating and seemed to be struggling much more than yours, but again, doesn’t mean it’s a different problem. Can’t think of what else you could do to troubleshoot short of taking it apart which I guess you don’t want to be doing when it’s still under warranty. ?

[Chris]

Just now, RobertI said:

Hi Chris, my SkyProdigy actually has the problem in the opposite (clockwise) direction to yours, although it doesn’t necessarily mean the motor is turning in a different direction. Does you problem happen at the same point on the azimuth axis, or does it exhibit the same issue wherever it is? Does it actually almost grind to a halt or just slow down? My mount didn’t exhibit the same oscillating and seemed to be struggling much more than yours, but again, doesn’t mean it’s a different problem. Can’t think of what else you could do to troubleshoot short of taking it apart which I guess you don’t want to be doing when it’s still under warranty. ?

Hi Rob, I'll double check but I'm sure it's anywhere on the azimuth axis. The first time I used it it ground to a halt completely whilst slewing to objects then after a while it would slowly crawl to the object and lock on and track. The same thing the second time once I'd upgraded the PSU. I've since upgraded the cable and thought that would solve it, I should have checked earlier really, got carried away with other stuff and assumed that was the issue as someone else had the same cable issue and a the cable upgrade solved it for them. 

It doesn't sound exactly like yours if yours didn't oscillate, and it does seem possibly a touch better with the new cable, it comes close to grinding to a halt but now keeps on struggling round. I am a bit worried about it struggling as it can't be good for it. I'm hoping this scope will last me years so don't want to put undue wear on it if the motor is struggling. 

Yes I don't think I should take it to bits as it still has about 20 months on the warranty. I'll run it by @FLO and see if they think something should be done at this stage.

 

[Chris]

I've emailed FLO now, so I'll just wait for their response tomorrow. I don't seem to have the best of luck with this kind of thing, or does everyone else have lots of scope issues?

[RobertI]

31 minutes ago, Lockie said:

I've emailed FLO now, so I'll just wait for their response tomorrow. I don't seem to have the best of luck with this kind of thing, or does everyone else have lots of scope issues?

I don’t think you're alone Chris! It will be interesting to hear FLO’s response, keep us posted. 

[Knighty2112]

1 hour ago, Lockie said:

I've emailed FLO now, so I'll just wait for their response tomorrow. I don't seem to have the best of luck with this kind of thing, or does everyone else have lots of scope issues?

It’ll still be under warranty still, so best to get FLO sort it out Chris. Hope all goes well.

Edited August 12, 2018 by Knighty2112

[alanjgreen]

Chris,

i had an issue with the Azimuth on my CPC1100 a few years ago. My issue was the opposite of yours - it would find the target but then not hold station while tracking, the target would slowly drift off centre and out of the side of the fov over a couple of minutes.

 

Eventually, I stripped the cover off and there is a big nut that holds the azimuth gearing in place. I read on the internet of a known issue where the Chinese workers would just leave this nut however tight they felt like and that it needed to be loosened a bit.

 

There is a test you can try, loose off the Azimuth clutch and spin the scope, it should complete a 360 degree spin easily or your nut is too tight.

 

I loosened the nut a bit (less than a quarter turn) until it was spinning more freely and then re-glued it in place with a drop of thread lock glue and found my issue went away. Maybe your nut is too tight and the motors cannot turn the scope. After this fix, I had several years of further use with no return of this issue

 

Have a search on cloudynights, there is a document you can download on this subject with step by step photos.

= I cannot find the document that I worked from but this is the nut that I had to loosen and re-glue

The key thing is that the scope should spin freely when the Azimuth cluth is off. Here is a doc I found that shows the strip-down steps (but this then goes on to replace the "bearing balls" which I did not need to do).

http://www.nexstarsite.com/download/CPCHowToReplaceFactoryOriginalNylonAzimuthBearingBalls.pdf

 

Alternatively, if you think the power cable has made an improvement then check the two pins on the scope side of the power socket. The metal piece that sticks up in the centre is made of two pieces and these two pieces can get pushed too close together and not make a good power contact. A small screwdriver can be used to just ease a gap between the two pieces so that the power cable makes a solid connection.

As said above, if its still under warranty then you can send it back but you can at least test the "does it spin freely" for now!

 

HTH, Alan

Edited August 12, 2018 by alanjgreen

[newbie alert]

Is it under 2 years old? If yes it has a 2 year warranty.. 

Take it back to your stockest and get them to sort it out.. my AVX played up..sent it back and it was good as gold..i was maybe without it for 2 weeks ish

[Chris]

1 hour ago, alanjgreen said:

There is a test you can try, loose off the Azimuth clutch and spin the scope, it should complete a 360 degree spin easily or your nut is too tight.

Hi Alan, thanks for your detailed reply  I've loosened the azi clutch and it does spin freely around, so that's a positive thing.

This actually made me stumble across something interesting, I noticed that if you do the clutch up lightly it slews really badly and grinds to a halt, if you do it up a fair/normal amount it will get nearly half way round before really starting to slow down, and if you really tighten it lots it will actually slew fairly well nearly all the way round before it starts to slow down. I could probably get away with it in use if I keep the clutch really tight, the only downside to this is you need it so tight that it's tricky to undo. It doesn't feel natural to tighten it so much but it does improve things to 90% normal it seems. 

The split in the power socket pin looks good, and I think I can now also rule that out if the varying amounts of clutch pressure seem to effect how well it works.

Thanks for the post, Alan  

[RobertI]

2 hours ago, Lockie said:

noticed that if you do the clutch up lightly it slews really badly and grinds to a halt, if you do it up a fair/normal amount it will get nearly half way round before really starting to slow down, and if you really tighten it lots it will actually slew fairly well nearly all the way round before it starts to slow down.

That’s weird but interesting Chris, must be a clue to the cause. Sadly I do not have enough knowledge about the inner workings to guess at the problem, perhaps someone else can. 

[Chris]

4 minutes ago, RobertI said:

That’s weird but interesting Chris, must be a clue to the cause. Sadly I do not have enough knowledge about the inner workings to guess at the problem, perhaps someone else can. 

It is a weird one Rob, I can't understand it either without stripping the mount down a little to see how the gearing works exactly, and I'm not going to risk voiding my warranty so won't be doing that. I really appreciate the input anyway, cheers  

[FLO]

21 hours ago, Lockie said:

I've emailed FLO now, so I'll just wait for their response tomorrow. 

Email received, we're on the case ? 

[Chris]

Thanks Steve  

For the benefit of others, Steve messaged me earlier after speaking to Celestron. They suggested I loosen the grub screw for the azi clutch a couple of turns to see if that resolved things before committing to shipping the CPC off for servicing. 

Unfortunately I've just tried this to no avail, so I'll be making arrangements with Steve for it to be serviced.

Thanks for all the input on the thread everyone, and of course to Steve at FLO  

  

[RobertI]

Did you get this problem sorted Chris?

[Chris]

2 hours ago, RobertI said:

Did you get this problem sorted Chris?

Hi Rob, thanks for asking  

The story is FLO gave me a choice between the adjusted/repaired CPC and a new one, so I opted for a replacement. I didn't hear any thing for a two or three weeks until just the other day when Martin at FLO emailed me and apologised as they wouldn't be getting any CPC800 Edges until sometime in November, so Martin gave me the choice again of having the adjusted model back or waiting for FLO to get a shipment. I've opted to have the adjusted model back so hopefully I'll have it back in the near future. I'll post when I receive it.

Just first world problems so I'm not sweating it   

Hope you are well?

Edited September 8, 2018 by Lockie

[RobertI]

Great stuff, at least you know the adjusted model will have been fully checked and adjusted (hopefully!). ?

[Chris]

Yeah very true, the reason I opted for a replacement was because of concern about the azimuth motor taking a bit of strain whilst trying to figure out what was wrong, but indeed I could get a new one with a problem that needs sorted. 

[RobertI]

Have they told you what the problem was and what the fix is?

[Chris]

It was sent to David Hinds UK, and the message back to FLO was that something just wasn't adjusted correctly. Poor QC in the factory then, all they had to do at Celestron before shipping is slew it in both directions on both axis and they would have spotted it had a problem. 

Edited September 8, 2018 by Lockie

[RobertI]

Unbelievable! ? Hopefully should be with you very soon then. 

Edited September 9, 2018 by RobertI

[Chris]

Hurrah! The scope is back and the azimuth no longer seizes up!

My heart was in my throat when it arrived because the box with the fork mount and OTA assembly was delivered upside down with the full weight of the mount pressing on the OTA and alt bearings! I'm assuming the delivery people turned the box the wrong way despite the box being extensively labelled "this was up" because the bottom of the box was open for some reason!? 

I did fear the worst, but the only downside seems to be that the Alt axis seems much louder than the other axis, so I bit of concern about keeping the neighbours happy. Thankfully if I reduce the slew rate to 8 it's about 4x quieter and won't wake the neighbours.

Looking forward to 1st light...take two.  

Edited September 14, 2018 by Lockie

[RobertI]

Good news Chris. ? The altitude axis on my SkyProdigy is also much noisier than the azimuth. Fortunately it's the azimuth that does most of the slewing so at least its the right way round! Keep us posted on first light part deux. 

[Cosmic Geoff]

I just found this thread while looking for a CPC800 stripdown guide.  I have been having a slight problem with the azimuth drive on my CPC800. I started a thread about it a while ago.

Now I have followed the directions above - slacken the azimuth clutch and spin the mount to see if it moves freely.   I find that it does not spin freely - there is some resistance and I can hear and feel a periodic clunking, which no doubt is associated with the change of note I can hear when slewing under power.

At least I have some idea what the problem is now.  Next step is to strip it down and see what horror lurks within. Maybe the plastic bearing balls.