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Runaway on DEC axis drive on CGX

Celestron equipment mount
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#1 skaiser

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Posted 26 October 2020 - 03:09 PM

OK
Here is a CGX problem that I have been experiencing with my DEC axis.
When the system is first powered up and after it has homed out on the switches.
During initial star alignment.
I drive the DEC and RA axis  at the same time, at full speed to point at my 2nd or 3rd alignment star.
During this slew of BOTH axis , the DEC axis will usually experience a “runaway” condition .
It will accelerate at faster than speed 9 then slow down then accelerate again , repeating, for as long as the DEC and RA axis are being slewed.

So I figured its probably a motor encoder problem. No
I swapped the drive motors between the RA and DEC axis and the problem remained with the DEC axis. I have to assume from this that problem is not in the motor/encoder.

So maybe a AC power supply problem? No
I replaced the 110VAC power supply with my 12VDC battery power supply (Deep cycle ,400 ah boat battery) and the problem still occurs.  So I have to assume this is not a problem with my AC power supply.

 

Looking back through the postings in this group I found this under “SOMETHING FOR CGX OWNERS” 
A  posting from Ed Thomas  , Deep Space Products
" Posted 22 July 2020 - 01:52 PM
Based on what you have done already, it's most likely and motor encoder problem on the RA.  An internal cable issue could also be the issue but it is much less likely."

 

In my case it seems to have been a INTERNAL cabling problem.
I opened up the access port located under the CGX carrying handle to check the cable bundle.
No cuts or bare wires but the cable seemed to be bunched up.
I worked on the bundle routing around the DEC axis , rotating the DEC head by hand until I was happy with how the cable was moving.
Problem has gone away.
I assume the cable was pulling on the connectors for certain motions and this caused the runaway motor actions.

Thanks ED for the clue on this.
Take care



#2 homerdt

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Posted 26 October 2020 - 03:30 PM

I've had the same experience with my CGE mount, only sporadically. And when it is happening I'll rap on the switch/motor housing and it stops, almost as if it is a switch hanging up. I've put out pleas for help with no response elsewhere to no avail.  


Edited by homerdt, 26 October 2020 - 03:31 PM.


#3 rmollise

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Posted 26 October 2020 - 03:30 PM

This genuinely sounds like a power supply issue...did you clean check the mount-side connector?

 

It sounds like you cured it, but if it recurs you probably need to hit the internal connectors with Deoxit and reseat them.



#4 rmollise

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Posted 26 October 2020 - 03:31 PM

I've had the same experience with my CGE mount, only sporadically. And when it is happening I'll rap on the switch/motor housing it stops. I've put out pleas for help with no response elsewhere to no avail.  

Same goes for your problem..BUT...CGEs are also prone to bad cables and bad connectors on the circuit boards.


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#5 homerdt

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Posted 26 October 2020 - 11:00 PM

Same goes for your problem..BUT...CGEs are also prone to bad cables and bad connectors on the circuit boards.

Thanks, I was experiencing problems related to the cables, but new cables recommended by a CN'er fixed the problem then, this problem is every once in awhile, seems like it's temp. related, only when it's cold,(40* or so) and in the SSE to S region.



#6 skaiser

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Posted 29 October 2020 - 09:43 AM

Rod

 Did not seem to be a power supply connection issue in my case .

For the past couple days I have tested the mount movement to see if it does the "runaway" . 

( it had been annoyingly consistent with this problem)

Now , Not sign of the issue at all.

 

I'll probably pull the cover off the "top" of the CGX to inspect the connection point to the control board.

Maybe see if I can put a strain relief point on the cable so it can't pull on the connector.

take care

Steve



#7 rmollise

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Posted 29 October 2020 - 09:49 AM

Rod

 Did not seem to be a power supply connection issue in my case .

For the past couple days I have tested the mount movement to see if it does the "runaway" . 

( it had been annoyingly consistent with this problem)

Now , Not sign of the issue at all.

 

I'll probably pull the cover off the "top" of the CGX to inspect the connection point to the control board.

Maybe see if I can put a strain relief point on the cable so it can't pull on the connector.

take care

Steve

Temperature problems in electronics spells one of two things...a failing active component...a transistor or IC OR...in most cases, a poor connection. Remove all connectors, hit 'em with Deoxit and be on the lookout for cold solder joints and stuff like that...good luck. :)




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