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Vixen Sphinx RA not working

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#1 shassell

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Posted 12 April 2009 - 09:38 PM

Hello.

I have a Vixen Sphinx SX mount. Last night I was doing a routine 2 star align as always. Aligned first star no problem. Selected next star, slewed and noticed that the mount was not rotating about the RA axis, and the StarBook never reached the target...just waiting with STOP messages on all buttons. In scope mode, I can hear the motor whirring which is normal...I think this means that the RA motor is working. I simply cannot use the RA for manual slew or GOTO via the StarBook.

I noticed no unusual sounds and there was no obstruction preventing the mount from moving prior to the loss of RA functionality. Temp, however was 29 degrees F. Brought mount indoors and allowed it to reach room temp. Still no RA. There is a SLIGHT difference in the motor sound when I attempt to move the mount with the controls, but no meaningful effect.

Any ideas?

Steve

#2 Bowmoreman

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Posted 13 April 2009 - 07:01 AM

Been a while since I had my Sphinx SXW... still miss the starbook fwiw...

but, I would occasionally have issues like this (either RA, or DEC, or both:

One thought: make sure you don't have your RA clutch too tight (or loose)... I'd loosen both RA/DEC clutches, rebalance my load, and re-tighten them...

Other thought (more likely from my experience): Also, the Sphinx is (semi-notoriously) susceptible to bad/low DC power, how were you operating it? On the provided D-cell battery pack? If so, make CERTAIN that you've a good set of fresh ones... I ultimately just always used the AC adapter, and never had problems again.

Unless you've modified your Sphinx, it comes from the factory with a very tight RA axis, so i doesn't take too much to make it "too tight"... for example if temperatures are much colder than they were we you did original setup and clutch tighening...

Good luck

clear enough skies

Good luck!

#3 adamsp123

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Posted 13 April 2009 - 07:32 AM

I had a problem whereby I had intermittent loss of RA followed by some very strange slewing actions.
What can happen is the cable between the starbook and mount can go open circuit, the cable is wrapped around a ferrite near one end and the tight wrap around can cause the thin cables inside to break, this can be easily determined by using a voltmeter set to ohms and see if you have an open circuit.
I fixed mine at work and also bought another 9 pin "socket housing" D-type - straight through to 9way "socket housing" cable - careful it is NOT CROSSOVER type which is the norm.
This is a known problem and the Ferrite is not required for operation so I chucked mine away.

Pete

#4 shassell

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Posted 13 April 2009 - 07:56 AM

I found an article online which instructs how to access the RA worm tension screw. Since the mount is under no warranty of any kind, and I have what I believe to be decent mechanical skills, I am considering accessing this screw and adjusting the tension ever so slightly in the loosening direction. I did verify the clutches were engaged but not overtightened. Also, I can see how colder temperatures might physically affect the wiring within the serial cable itself. I will look into all of these possibilities...luckily we have some cloudy nights (I am not a paid endorser of CN.com ha ha) coming up here, so I have some time to dust off my tinker hat.

#5 ArchRival

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Posted 16 April 2009 - 03:18 AM

Hi shassell may i know if you solved your problem? I'm experiencing the exact same problem on my Sphinx. The RA axis sometimes refuses to move during Goto, but when i give the mount a push it starts moving. Sometimes it stops when it's supposed to track. I'm still running on 8 D cells. I'm guessing it's the power but i'd like confirmation that this is indeed the cause.

Thanks.

#6 shassell

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Posted 16 April 2009 - 03:07 PM

No, unfortunately I have not resolved the issue. I am running on AC power, so I have sufficient juice. I do know that running on low batteries can also cause this to occur. Try fresh D cells or AC power. I bet you get better results.

As for me, it seems the shaft on which the worm gear sits is frozen. It turns JUST BARELY in one direction or the other, then the motor simply labors. I am risking burnout unless I turn off. Will probably ship off to Vixen to have them tell me I just needed to flip the rotary-channel canooten valve or turn the biokinetic corky-flapper.

#7 ArchRival

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Posted 17 April 2009 - 09:02 PM

Thanks for the info. I'm getting an AC power adaptor which i hope solves the problem.

Sounds like some parts of your mount have seized. Anyway, wish you luck for your mount. Hope you get it to work soon.






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