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Equipment Discussions >> Mounts

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Hilmi
Post Laureate
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
G11 with Gemini II acting weird
      #5566219 - 12/11/12 04:17 PM

OK, So I have not used my mount for a week and last I used it, it was perfectly fine. I traveled for a week and when I came back I hooked up my adapter to for the optec lepus reducer which pushed my camera further out. So I re-balanced the mount as per my usual procedure starting with Dec balance then RA.

I powered the gemini II and durring my first alignment slew, the RA stalls. Usually when it stalls, it will respond after for example loosening the worm gear meshing. This wasnt the case, the motor was super hot. So I disconnected everything and waitted for the motor to cool.

I tried reversing the RA and Dec cable and couldnt see a problem with the cable, so i reballance. Same issue.

After a few restarts, It agree's to slew, but it keeps on stalling on both Axis, as if it is not getting enough power. It is hooked up to a 16.5 V laptop power supply and I validated this through the gemini web interface. Any idea what's wrong?


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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5566773 - 12/11/12 11:28 PM

Bump! Need help, I'm going to a Star party tomorrow. Also posting on Yahoo groups now

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blueman
Photon Catcher
*****

Reged: 07/20/07

Loc: California
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5566885 - 12/12/12 01:16 AM

Check the power supply for correct voltage.
Blueman


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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: blueman]
      #5566926 - 12/12/12 02:09 AM

Getting 16.5 V according to the Gemini II web interface.

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mega256
scholastic sledgehammer
*****

Reged: 05/10/07

Loc: N of Tampa
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5566942 - 12/12/12 03:01 AM

Wonder what the power looks like under a load?..
You might look at the voltage when doing a goto, and you may even hold the scope while slewing....There may be a poor conection to the power supply,and might show up only under load..Now that its doing it in both motors the most common thing would be power or connections to power.A tarnished conector might do this.


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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: mega256]
      #5566981 - 12/12/12 04:56 AM

Gonna shop for CRC conact cleaner today. Hope it works

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Bowmoreman
Clear enough skies
*****

Reged: 09/11/06

Loc: Bolton, MA
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5567031 - 12/12/12 06:22 AM

I occasionally had power related issues with my Gemini I until I just broke down and bought a dedicated 80 Amp marine battery for it... Nary a problem in the year since... Ac adapters are prone to flakiness in my experience... Volts might be ok, but you might get amp issues, or vice versa... Good luck

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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: Bowmoreman]
      #5567041 - 12/12/12 06:40 AM

Dave,

I actually have a brand new car battery that I had never used before to power anything, I had it on my battery tender to keep it charged. So I hooked it up to trouble shoot last night and to my disappointing it turned out to be giving out 11.2 V which is way too low to power the mount.


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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5567447 - 12/12/12 12:10 PM

Slews now working but movements are jerky and my tracking is horrible. Im starting to really dislike this mount

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gdd
Pooh-Bah


Reged: 11/23/05

Loc: N Seattle suburb, WA
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5567522 - 12/12/12 12:44 PM

Quote:

I powered the gemini II and durring my first alignment slew, the RA stalls. Usually when it stalls, it will respond after for example loosening the worm gear meshing. This wasnt the case, the motor was super hot. So I disconnected everything and waitted for the motor to cool.





Motors damaged?

Gale


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Startraffic
professor emeritus
*****

Reged: 02/12/06

Loc: Lat. 39.143345, Long. -77.1748...
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5567550 - 12/12/12 01:04 PM

Hilmi,
Answered on Yahoo group too but....
I'd check for either grit in drive train in you're in a high dust area IIRC. If that's clean then I'd look at the Worm mesh. Too tight will cause binding, motor overheating, burnouts, or if just a little too snug then Lagging errors, poor tracking , etc.

Clear Dark Skies
Startraffic
39.138274 -77.168898


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Hilmi
Post Laureate
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: Startraffic]
      #5567744 - 12/12/12 02:38 PM

I actually took your suggestion and took it a step further, I went and polished the worm gear by hand using some mild non abrasive polish, its now far smoother, The slews are quieter, but my tracking is not as good as before this saga happened. I suspect you are right and my motor is on its way to kicking the bucket. what unfortunate timing. Just when I got my focal reducer going

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Startraffic
professor emeritus
*****

Reged: 02/12/06

Loc: Lat. 39.143345, Long. -77.1748...
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5569768 - 12/13/12 07:14 PM

Hilmi,
You haven't had it that long & you've had "issues" with it all along, Why not email Scott or Russell & see if they'll send you a new worm? Can't hurt & they just might. If they say no then a new Brass high precision worm is $65 USD + shipping which would still probably be under $100 USD. Still worth doing.

Clear Dark Skies
Startraffic
39.138274 -77.168898


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Hilmi
Post Laureate
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: Startraffic]
      #5570386 - 12/14/12 07:06 AM

Motor kicked the bucket as confirmed by the hours wasted setting up under perfect skies and finding the motor dead

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Startraffic
professor emeritus
*****

Reged: 02/12/06

Loc: Lat. 39.143345, Long. -77.1748...
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5570824 - 12/14/12 12:59 PM

Hilmi,
That would be Murphy paying you a visit. He happens to have a permanent place in my back pocket, right beside my wallet.

Clear Dark Skies
Startraffic
39.138274 -77.168898


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mega256
scholastic sledgehammer
*****

Reged: 05/10/07

Loc: N of Tampa
Re: G11 with Gemini II acting weird new [Re: Startraffic]
      #5570988 - 12/14/12 03:04 PM

I bought a new motor (hd) ,used the old for a spare..The new motor is very much stronger!So much that I bought a ($35 spare gear box,just incase)I can get a much better fit on my RA worm...works great.And runs cool compared to the old one moving mt C14..The new losmandy motors seam much better than even the maxum..Wasnt cheap,but solved my problem.I called and they had it to me in 2 days.(Florida)good luck..

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Hilmi
Post Laureate
*****

Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: Startraffic]
      #5570993 - 12/14/12 03:06 PM

Murphy is a secret agent of whoever is managing the US economy. It's always some gadget that dies on me and the parts need to be shipped in from the US. He probably also owns shares with Fedex, UPS and USPS.

Anyway, jokes aside. When I took the mount apart to clean it, I could not find any grit in the gears, but I did find that one of the two cubes that hold the worm gear in the OPWB was for some reason not seated properly. I find this odd, I checked it last time after assembly, I could have missed it, but I recall being rather thorough. So I guess the worm was binding and that overloaded the motor, which is why my second motor also died out when I swapped out the motors.

Anyway, I took the chance today to use a polishing wheel on my Dremel tool and I polished both the worms as per some instructions that I found online which indicated that this same process gave very good results for that user. Thing is, he used a very specific type of polish that's not available in our market. I used some liquid chrome polish, which isn't all that abrasive. Running my finger over the gears, they feel smoother, even that damaged one that I had put on my DEC axis, the scratches on it just feel a bit rounded. Now I need to budget for new motors before I can do any imaging. This time before I put on the motors I am pulling the entire mount apart for a thorough clean up.

Edit: $225 a pop without shipping! I need two of them too! I need to sell something so that I can fund these motors.

Edited by Hilmi (12/14/12 03:09 PM)


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terry59
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Reged: 07/18/11

Loc: Colorado, USA
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5571181 - 12/14/12 05:14 PM

Quote:

I need to sell something so that I can fund these motors.




Children? Life insurance policy?

Edited by terry59 (12/14/12 05:15 PM)


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Hilmi
Post Laureate
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: terry59]
      #5571649 - 12/14/12 10:01 PM

Unfortunatly. I have only 1 child. The wife would notice.

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Joe C
sage
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Reged: 11/29/08

Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5571687 - 12/14/12 10:23 PM

Then the wife it is

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Hilmi
Post Laureate
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: Joe C]
      #5571797 - 12/14/12 11:47 PM

I'm saving that for when I decide to buy an AP1600 and the kid for when I want to put a 6" AP refractor on it.

But with all seriousness, I'm still confused as to what caused the motor burn out. I'm not convinced it is to do with the with the cubes holding the worm blocks as I am very sure I had them installed properly after I last took them off. I even remember checking for gaps to confirm I had proper seating. After this, I used the mount for at least a week with smooth performance, so that can't be it. When I balance the mount, it does not move all that freely, could it be that I thought it was balanced but it wasn't?

I think my warranty is out, but I will attempt to request a goodwill replacement of the motors, because as mentioned earlier my mount never really worked up to expectations.


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Hilmi
Post Laureate
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5572173 - 12/15/12 08:48 AM

Scott is a great guy, I told him my motors where burnt out and he offered to send me new ones if I sent him the old ones back.

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terry59
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Reged: 07/18/11

Loc: Colorado, USA
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5572381 - 12/15/12 11:09 AM

You can't beat that

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mega256
scholastic sledgehammer
*****

Reged: 05/10/07

Loc: N of Tampa
Re: G11 with Gemini II acting weird new [Re: terry59]
      #5572708 - 12/15/12 02:52 PM

still BUILT in the USA..........with USA service.

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Hilmi
Post Laureate
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: mega256]
      #5618555 - 01/12/13 07:52 AM

Just got my replacement motors from Scott. Communication was poor throughout the process as I was left in the dark for almost a month with no idea what's going on, but... I am still very very very happy. I just got a package in the post today with the brand new high torque motors. That's actually a paid for upgrade for the mount and I got it as a warranty replacement for my old motors. I'm a happy man Going upstairs to install these new babies right now!

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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5618609 - 01/12/13 08:46 AM

Found the cause for failure while installing the new motors indoors. It was the new gearbox that I had gotten just 2 months before the problem to replace one which had a rounded screw thread for the motor. it had seized up

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Dan Finnerty
sage


Reged: 09/11/11

Loc: Pasadena, CA
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5619446 - 01/12/13 04:58 PM

Hilmi,

What was the problem with the bad gearbox? I'm curious to know for future reference.

The gearboxes seem to be the Achilles heel of the G11. Otherwise an excellent mount, but I have had repeated problems with the gear boxes. Mostly my fault (bonking the RA motor and breaking the plastic pins on the gear box for example).

Are the new high-torque motors any longer than the stock motors? I am thinking of upgrading, but am leery of making the RA motor project out even further and increase the chance of me hitting it again...

I'm very interested in hearing how this works out for you.


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wasyoungonce
sage


Reged: 06/07/07

Loc: Land Downunder
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5619846 - 01/12/13 09:35 PM

Jeez Hilmi...you're having a bad run of late...were you hexed by a gypsy or somethin?

Edited by wasyoungonce (01/13/13 07:01 PM)


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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: wasyoungonce]
      #5619917 - 01/12/13 10:18 PM

cup half full
I got a free upgrade.
Gear box had seized somehow

Edit: In response to the motor length, since I don't have them side by side, I cant compare the size. Visually when not next to each other they look about the same size. Somebody did a comparison online on the Gemini II yahoo group and it was mentioned that they are slightly longer, can't recall how much longer.

They are also louder while slewing, but I never did find this a big deal, because unless you are sitting very close to your sleeping neighbor, it shouldn't make a difference.

Edited by Hilmi (01/12/13 11:30 PM)


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Raginar
Postmaster
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Reged: 10/19/10

Loc: Rapid CIty, SD
Re: G11 with Gemini II acting weird new [Re: Hilmi]
      #5620149 - 01/13/13 02:53 AM

So, do you need to replace your gearboxes now?

Chris


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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: G11 with Gemini II acting weird new [Re: Raginar]
      #5620190 - 01/13/13 05:13 AM

Nope. I had a spare I'll find out tonight if the clouds clear up. It is abnormally cloudy, that's a good sign, it indicates that something good related to astronomy equipment just happened.

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