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Hi all,

 

After updating my legacy HC to the 99.22 (I had to, because of the GPS rollover issue) and the MC to the 5.23 firmwares (siply because it was there, and I've got greedy), both acquired via Teamcelestron, my CPC was operating normally until, all of the sudden, its altitude motor stopped working. I've uploaded a video at youtube showing what happens:

 

https://youtu.be/p2cHJkPt9Vc

 

As you can see, I don't get any error message in my HC but, if I try to move the scope in altitude, nothing happens (no movement, no motor noises, nothing). When I release the clutch and move the scope manually in altitude, it does move but has a weird noise by the same place where previously it used to make a snap one, which I already reported to celestron tech support once, and even made a video that I also uploaded to youtube:

 

https://youtu.be/KCc69eUSbeY

 

I've already seeked help from Celestron Tech support (and the folks at Cloudy Nights) but any help from you would be very much appreciated. Best regards,

 

NV

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This is a CPC800? I own one.

I have no idea what the problem is. Maybe take the covers off and have a look. Or arrange to get it serviced? You are sure it is not a bad button on the handset?

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Hi Cosmic Geoff. Yes, it is a CPC 800 GPS (the 50th annyversary carbon fiber one). This is pretty much what Derik (the firm engineer at TeamCelestron) told me to look at but, before start dissasembling, I was hopping that someone around here could recognise its symptoms and provide me with directions... One can always wish...

And no, getting it serviced is not an option, considering where I'm living at :-(.

Regards,

NV

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If you look on the Cloudynights forum you should find some dismantling hints for the CPC800.  At the back of my mind is something about rotary encoders with glass discs ? so check that and take care.

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Hi all, me again...

 

I've opened the mount and retigtened all the connections with no improvement on the situation. Then I decided to switch the dot connector with the square connector (see the last picture in the set below) and, after switching on the scope, the up/down buttons in the hand control moved the scope in azimuth, instead of altitude, while the left/right buttons did nothing. 

57441221_WhatsAppImage2019-05-04at18_07_27.thumb.jpeg.83c8a6501c9223da1eb59f8c362c1cc6.jpeg

A picture of the scope with the arm without the cover.

1679016839_WhatsAppImage2019-05-04at18_08_11.thumb.jpeg.dfd7193575a4ac731bea18480c272b89.jpeg
A picture of the board that is placed in the arm.

1822824317_WhatsAppImage2019-05-04at18_09_04.thumb.jpeg.c7d1ec847b1853e397124198d144eb15.jpeg
A closeup of the connectors which I switched positions.

 

I'll ask a colleague at work to look at the boards, just in case any component has been damaged but, as far as I can see, everything looks fine, even the altitude motor...

 

NV

 

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Posted (edited)

I have just read your post and tried to follow what you have done and it seems to me that swapping the connectors has eliminated the hand set and the board. Switching the drive output over tested the buttons and the driver so my guess is that is that you have a motor problem.

Looking at the wiring going to the motor it looks like a DC motor (the two wires on their own and the multi connector a positional encoder. If you have a multimeter then I would disconnect the two wires either side of the motor and check for continuity across the motor connections and see if its open circuit.

It might just be a stuck brush so a sharp tap on the side of the motor might unstick it.......you never know you might be lucky.

Best I can suggest

Edited by Tomatobro
uodate
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Yes, as Tomatobro said, your connector swap indicates the problem is with the Dec motor or the cable connecting it to the board. Check that the individual pins on the Dec motor connector are fully pushed into the socket housing.

Alan

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Thanks Tomatobro and symmetal, yes my thoughs also, the motor seems dead (which could also explain why lately, when I was using the scope with the wedge and there was more strain on the motors, the objects slowly drifted away in the FOV). Pity I don't have a multimeter here (this is one of those things I've always meant to buy but I never had), I'll try to get hold of one as soon as possible but, by looking at the motor and its two cables, I don't see how to unplug them without damaging them. Should I simply pull them out?.

Regards,

NV 

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The two wires going to the motor body look as if they are soldered to tags on the motor and coverered with heatshrink so no they won't pull off. The wires going to the connector at the end of the motor look like low profile plug and socket which should pull apart. Apply a little leverage to one end with a small screwdriver to see if it moves and then apply a little leverage to the other end. Don't pull on the wires themselves with any significant force as you may just end up pulling the wires off. As you say a multimeter is a very useful tool in this situation. Good luck. :smile:

Alan

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Or simply put the tester's probes (if they are thin enough) in their corresponding socket in the bus of cables at the other end (where it connects with the board).

By looking at how Celestron sells this componnent, it seems like you have to buy the whole thing. How to install it is yet another story because I don't see an easy access to one of the screws... Ah well, I'll cross that bridge when (if) I get there.

https://www.celestron.com/products/motor-azmra-for-cpc-series-telescopes

Thanks a million Alan (symmetal) 

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If the probes aren't thin enough just wrap a bit of wire round the probe tips and poke the wire into the connector. If it's still powered make sure you don't short anything out. :wink2:

A motor that has burned out due to over stressing it will usually have a distinctive smell which will linger for days after. If your dec motor doesn't smell 'odd' it may be OK though that doesn't rule out a wire connection failing internally.

Hope the replacement if needed isn't too expensive.

Alan

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I've got hold of a multimeter and found out that there is no continuity across the motor connections, so it looks like I have an open circuit issue in the motor (which, by the way, doesn't smell burnt). I think it is time to dissasemble it to try to find out what is wrong inside or to order a spare motor from Celestron.

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Good that you've narrowed it down to the motor. If you're able to disassemble it it's worth having a look inside. :smile:

Alan

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A small DC motor might have permanent magnets for the field and a commutator to feed the rotor. The likely failure area is then the commutator & brushes.  Given the modest volume of CPC scopes manufactured, I doubt that the motor will be unique to Celestron.  You might try giving the motor a twirl and a squirt of cleaner/ lublricant (sold as "3 in 1" over here.) 

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Thanks symmetal and Cosmic Geoff. Derik (at TeamCelestron) told me that my multimeter test confirms that I either have a problem with the alt motor or in the wires leading to the alt motor. Also he informed me that the motors don't usually fail open. They fail in a short. So since I don't have continuity he would guess a bad connector is the issue. However, Celestron sells the motor and the cable attaching it to the PCB as an assembly, so I've already asked for a replacement unit from the local dealer.

NV

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Posted (edited)

Hi all,

Finally I received the motor and, before I did the replacement I conected it to the board in order to test it and, yes, as you can see in de video below, it did work (hurra!):

https://youtu.be/rmx6skIi_1c

However, after installing it, I noticed some oscillation in the entire motor set, as you can see in the video below:

https://youtu.be/m94rUzcQaBU

Since I never saw it working before its failure, I don't know whether such oscillating movement is normal or not. Can you please help me out with this?.

Silly me, I've justo noticed that I had my phone's camera capturing video in slow motion so it is hard to noticed the oscillating movement. Ah well, I've uploaded yet another video at normal speed below:

https://youtu.be/1MV6Dd9u9O0

Hopefully this one is more clear :-).

Best regards,

NV

Edited by NenoVento

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The oscillations may be due to the grubscrews in the coupler not being aligned and tightened correctly.

Make sure that one of the pair is properly aligned with the flat on the motor unit output shaft and fully tighten this one first, then tighten the second one.

It is possible you have tightened the second one fully which would cause the shaft to tilt in the coupler.

Hope this helps.

 

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Posted (edited)

Thanks @Lonestar70 but this is exactly what I did. Anyway, I uninstalled it and looked at the flat part and it did have the mark of the screw, so I did place it properly... Then I reminded that the azimuth motor was exactly the same and decided to take a look at it and, yes, as you can see below, it also oscillates:

Therefore either they are both misinstalled or that is the way they are ment to operate. Hopefully tomorrow (or rather later today) I'll get a chance to try it out properly.

Best regards,

NV

Edited by NenoVento
Typos

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Hi NV,

Glad to see it's all working again with the new motor. The movement looks like it's normal behaviour given the way the motor unit is attached. You could loosen the three screws holding the motor unit to the scope and see if there is some play in allowing it to move sideways. You may find a position where the oscillation is minimised. Very thin spacers under one or two of the screws would probably help too. As the oscillation is at a low speed it's not causing much harm so whether you want to try is up to you. :smile:

Alan

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Thanks @symmetal, I think I'm going to see how it behaves by trying gotos and doing tracking before. If it does work properly (fingers cross), I'll let it be as it is now.

By the way, from the three screw sockets only two are actually in use (by its corresponding screw, I mean). The third is not needed because the motor is fixed to a kind of holder which is the one that lets room enough for the oscillations to hapen without afecting much to the shaft. Pretty simple but well thought of engineering, I think.

NV

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Hi all,

 

This is the final chapter of this story which, as you can see below, had a good end 🤩 :

Saturno3mDeRotL_2019-08-10-0002_7-2019_08_10_01_01_10-DeRot_g6_ap292_convRegFW.png.0f267a4f25330acb70bc3fb48445fc08.png
I took this picture of Saturn last night from my terrace (by the seaside, with a lot of dew coming from the sea and leving the corrector plate pretty dirty) and it was such a pleasure to have my CPC not only back to life, but operating way better than it did before . The target stayed centered and practically unmoving for minutes and minutes, without having to manually recenter it!... Such a pleasure.

Now the technnical details for the picture (in case you were interested):

The gear:

  • 50th Anniversary Celestron CPC 800 GPS XLT
  • GSO 2.5 Barlow Lens
  • Risingcam GPCMOSS02000KMA
  • ZWO Luminance filter (I also took RGB videos but I haven't had time for processing them yet)

The software:

  1. ToupSky (I took 3 minutes @ 46.69 gain and 15 ms)
  2. Autostakkert
  3. Registax (slight touch with wavelets)
  4. WinJUPOS (for derotating the video, then back to step 2.)
  5. The Gimp (color curve adjustment)

Regards,

 

NV

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