Author Topic: New CGEM DX plagued with problems.  (Read 620 times)

cromsotejbi

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New CGEM DX plagued with problems.
« on: January 08, 2018, 01:50:52 PM »
This post is to request opinions on what to do next. Please follow this sequence and let me what you would do.

I got interested in AP and bought a CGEM DX and EdgeHD 11 in January. Had I known then what I know now I would have sent the mount back for corrections, but I didn't.

The mount firmware was current but had a tracking flaw just discovered when I bought it. Derik with TeamCelestron let me know he was releasing a beta fix so I downloaded and tried to load it. It took a week of tries to get it to load. I think there is a hardware problem in the motor control board.

Occasionally the motor control will start running on its own. It will do it for a few sessions and then start working correctly. It's had it own way about four times now. I have tried cooling and warming the board when it is sick but makes no difference. Visually I cannot see any solder defects under magnification. Contacts are clean too. The direction control buttons have no effect except If stopped and I press one it usually runs RA west with no control after it starts. It does this for awhile the return to normal. I can power it up without the HC and it still starts running after a few seconds. I can power it up without the HC and it still starts running after a few seconds. It will start running in the star alignment steps when the first star name appears. Power off is the only way to stop it.

Now for mechanical problems. I bought a HyperTune kit. Now I know how it is assembled and how it works. I discovered too much backlash in the RA and DEC worn drive. The RA worm was tight. The preload nut did not have thread lock on it. It probably turned while running and tightened. So in the process of adjusting the worm backlash it started its misbehaving again.

I am reluctant to send it to Celestron. Manufacturers fix problems the less costly way and that may be simply sending another unit to the customer. I don't want another unit after fixing the mechanical problems assuming they have one. I made a request yesterday with Celestron to examine my motor control board. I have not received a reply.

I can buy a board from Deep Space Products but I need to be sure the problem is in the board and not an encoder or indexer problem.

What are your thoughts?



housletica

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Re: New CGEM DX plagued with problems.
« Reply #1 on: January 10, 2018, 07:47:26 AM »
1) Beta firmware to fix a bug in Celestron's code. That's on Celestron to make it right.
2) The hardware is a bit trickier since you performed the hyper-tune yourself, likely partially invalidating the warranty. (maybe someone else can clarify how that would work and/or whether my comment wrt to it is true or false)

Jay Garcia

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Re: New CGEM DX plagued with problems.
« Reply #2 on: January 10, 2018, 09:38:00 AM »
Have you tried doing a reset on the HC? I would do that first. It likely wont fix the problem but its a good place to start.

The mount can't run on its own unless its getting a signal to do so. The encoder is only going to tell it where it is at ( wrong or right). I would make sure you have good power supply source. Either new batteries or a good power supply. If the mount is getting less than the needed 12 volts it can do very goofy things including the possibility of moving on its own.  If you are sure the voltage is good, you have done a factory reset of the HC and you mount is set at its index marks (PG 8  http://www.celestron...8cgemdxmanl.pdf) the only possible thing that I can think of is a short on the motor board.

John Jankowski

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Re: New CGEM DX plagued with problems.
« Reply #3 on: January 11, 2018, 04:29:06 AM »
Try plugging the HC into the AUX port.

Eric Ayyagari

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Re: New CGEM DX plagued with problems.
« Reply #4 on: January 11, 2018, 10:08:16 AM »
Quote
1) Beta firmware to fix a bug in Celestron's code. That's on Celestron to make it right.
2) The hardware is a bit trickier since you performed the hyper-tune yourself, likely partially invalidating the warranty. (maybe someone else can clarify how that would work and/or whether my comment wrt to it is true or false)

The firmware was tested and no problems were found. It was released as version 6.51.

As for warranties, everyone seems to be afraid of invalidating warranties. No one reads them. In a nutshell, if you break it you pay for it. If it's a manufacturer fault they fix it. HyperTune is not a modification, just an adjustment to improve its mechanical functionally. I'm not concerned about that. I just want the control to work.

blufdestholreng

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Re: New CGEM DX plagued with problems.
« Reply #5 on: January 11, 2018, 03:03:42 PM »
My AVX arrives tomorrow, I have my fingers crossed it works out of the box. However, I am going to switch out the gears to a belt drive on the dec and some other small changes to help improve the overall performance. From what I understand the grease they use in the mounts is thick and tacky and I will likely find something else, like a tacky chain lube but much thinner. 

I have a hard time getting my head around that these mounts aren't trouble free right out of the box.

Justin Prasad

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Re: New CGEM DX plagued with problems.
« Reply #6 on: January 14, 2018, 06:40:09 AM »
The power is good, 35Ah 12.9v never below 12.0. The power pack runs everything (mount, camera, computer) and has a digital voltmeter which I monitor.
The control works just fine when running correctly then no control at all when going bezerk! I don't knowingly change anything between the two conditions. I could turn it on right now and have it working correctly, OR NOT. I don't have a clue when it will change. It's a hardware problem!

I was advised by Celestron to not plug the HC into AUX. Another complaint is Celestron has not updated the HC functions from the NexStar to the NexStar+. The menu is different and I have marked up the differences I have found. I would have thought the CGX manual would have been updated for the NexStar+, not so. They omitted that part of the manual. If anyone knows where the menu structure is for the PLUS I would like a copy. Keep in mind that I am new to telescopes and mounts so I need ALL the documentation I can get.

I will contact Deep Space Products and get their opinion. If I was sure the problem is in the motor control I would just buy it and go back to imaging.

barlaliblo

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Re: New CGEM DX plagued with problems.
« Reply #7 on: January 18, 2018, 04:30:46 AM »
Quote
My AVX arrives tomorrow, I have my fingers crossed it works out of the box. However, I am going to switch out the gears to a belt drive on the dec and some other small changes to help improve the overall performance. From what I understand the grease they use in the mounts is thick and tacky and I will likely find something else, like a tacky chain lube but much thinner. 

I have a hard time getting my head around that these mounts aren't trouble free right out of the box.

I'd suggest you try the mount first and only fix it if it doesn't do what you want it to do. My AVX guides really well out of the box.

Noty Tarabori

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Re: New CGEM DX plagued with problems.
« Reply #8 on: January 25, 2018, 02:40:40 PM »
What do you mean when you say it is going "bezerk?" Is that was Derik calls "ludicrous" mode?

MJB

wordpuzzlesubc

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Re: New CGEM DX plagued with problems.
« Reply #9 on: January 31, 2018, 12:20:06 AM »
I highly skeptical about this. If it were a firmware problem, other folks than you would be affected, and I'm not hearing about a rash of CGEM runaways (or on the other mounts. All the GEMs use the same firmware). That doesn't mean your particular mount doesn't have a problem, which can range from power/power cords to motor encoders.

Best bet to start with might be to contact a local amateur (from the local club) familiar with these mounts to help you out. Do that before you ship it to Celestron.

tioraigenroi

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Re: New CGEM DX plagued with problems.
« Reply #10 on: January 31, 2018, 10:44:27 AM »
Quote
Quote

1) Beta firmware to fix a bug in Celestron's code. That's on Celestron to make it right.
2) The hardware is a bit trickier since you performed the hyper-tune yourself, likely partially invalidating the warranty. (maybe someone else can clarify how that would work and/or whether my comment wrt to it is true or false)

The firmware was tested and no problems were found. It was released as version 6.51.

As for warranties, everyone seems to be afraid of invalidating warranties. No one reads them. In a nutshell, if you break it you pay for it. If it's a manufacturer fault they fix it. HyperTune is not a modification, just an adjustment to improve its mechanical functionally. I'm not concerned about that. I just want the control to work.
Fair enough. I wasn't aware the firmware had been ruled out. I must have missed that in your opening comments.

I'm not "afraid " to invalidate a warranty, but there are levels of DIY that can cause warranty invalidation, depending on a given vendor and their terms...

Personally, I'd send the rig back to Celestron for servicing if I couldn't resolve runaway problems on a new mount, modified or not...

erafquacor

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Re: New CGEM DX plagued with problems.
« Reply #11 on: February 08, 2018, 10:23:23 PM »
Problem found! This condition is a wreck waiting to happen. If you own a CGEM series using the firmware (6.51) NEVER leave the mount unattended. This condition could be in other mount firmware too.

The problem with my mount is an intermittent RA motor encoder. There is one place (maybe more) in the control sequence that an encoder failure will a cause continuous runaway, only to be stopped by your camera colliding with the tripod or cable wrapped tight enough to stall the motor if you don't catch it first.

This problem was in the new unit I purchased in January and it's taken six months to figure it out. Celestron's customer service has not helped enough to guide me in the right direction. After doing a HyperTune and finding mechanical problems that should not have been I am reluctant to send it to Celestron.

I inquired with Ed at Deep Space Products and his suggestion was to swap the RA & DEC motor connectors and see if anything changed. It did! I repeated the symptoms between the two motors several times. It was clear the control is not seeing the motor movement and hangs leaving the motor powered.

I ordered an new motor from DSP and got it in two days. I plugged it in and while holding it I could feel the motor jog then go into tracking speed. The condition I was able to repeat was entering the two star alignment and stepping to the point of "Select Alignment, Two Star Align" Upon pressing ENTER it presents a star name and should wait for you to ENTER or select another star. Prior to your selecting the star it goes into tracking mode and that is where the bad encoder causes the problem. There are probably many more places in the program where it goes into tracking and would cause the same problem if the encoder fails to work at that point.

The firmware needs a trap to catch this condition, send an error message and stop the motors. DON"T LEAVE YOUR MOUNT RUNNING UNATTENDED!

The next clear night I will be testing long exposures for guiding performance. I'm confident it will work correctly for the first time.

Roger Dixon

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Re: New CGEM DX plagued with problems.
« Reply #12 on: February 09, 2018, 10:34:46 AM »
As a rule, if you have a runaway with one of the Celestron mounts (where servos and encoders are used), the first thing to check is the power and power connection. Intermittent power or poor power can cause many odd things to happen. The next suspect is the firmware which can be corrupted by a number of different issues (including power issues). After going through those steps, the most likely cause remaining is the motor encoder. Motor board problems don't usually cause runaways. They more often result in something simply being dead. When you are down to the motor encoder being the most likely suspect, try switching the motor leads and see if the problem stays with the axis that was originally having the problem. If it does, then the motor encoder is the issue. If the problem switches axes then it could come down to a board problem (which is significantly more expensive), I have found this to rarely be the case.

Occasionally, the encoder problem can be as simple as some kind of debris in the encoder (e.g., a spider web), or a broken/loose encoder disk. More often it is a bad encoder circuit board though.