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A bit of trouble with a G11 Any suggestions?

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#1 mdowns

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Posted 22 October 2012 - 07:45 PM

In the past week I picked up a cg11 setup. Last night was the first time I set the system up. Tripod is level and I used the included Losmandy polar scope to zero in my alignment.However my drive is'nt tracking.I do have power to the unit and the hand controls work fine.The package did not include the orginal power supply.The manuel says 12V,.500 MA so I went to radio shack and bought such a unit.I ran a cord out from the house and hooked up to the power supply and then to the 12V in slot. Everything lights up and of course the hand controller works but thats it,no drive.The cnighter I bought this from told me that the mount does need relubed but was nonetheless tracking fine and I certainly believe him. He suggested the heavy shift trick with the weights but I dont think thats the concern.I once had a gm8 with an 10" meade sct and the thing tracked perfectly though I was always changing the weights around for different OTAs. I really think either I'm missing something extremely obvious or I suspect that the power supply (though matching the manuels specs) is'nt enough.I just read on another thread that some use power supplies on thier G11s with much more than half an amp and even with more voltage. Perhaps newer models require more than this old model (1995 I think). Anyway I would certainly appreactiate any suggestions no matter how obvious.Many thanks!

#2 mdowns

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Posted 22 October 2012 - 08:01 PM

Heres a pic of the main stuff

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#3 mikemxyzzy

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Posted 22 October 2012 - 08:48 PM

I would expect it to take more current when moving with the hand controller than when just tracking, so I would not suspect the power supply. I have a CG-11 and it ran just fine from a Radio Shack 500mA power supply. It may have been the same mode you have. I would also expect that if the bearings were sticking or binding it would cause more problems when moving the the hand controller than when tracking.

How do you know it is not tracking? Can you see if the RA motor is turning at all when it should be tracking? You can take off the dust cover from the RA worm and see the coupling from the motor to the worm, so it is easy to see if it is turning.

If you don't have it polar aligned it will not track the sky even though it is moving the RA axis. From the photo it looks like it has the polar alignment scope, so it should be possible to get it aligned.

#4 mdowns

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Posted 22 October 2012 - 09:20 PM

Mike,
As I mentioned the mount is polar aligned.I can hear the ra motor,its getting power, but there is no tracking. How do I know? If I understand your question the answer is simple.Objects drift very quickly out of the FOV,as if the motor were off.I hav'nt removed the motor cover yet.I keep thinking that this is truly simple,some kind of oversight on my part.

#5 John Miele

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Posted 22 October 2012 - 09:40 PM

Are the clutches engaged? Could the RA tracking direction possibly be accidentally reversed? Although I'm not sure the CG11 has such a setting :question:...John

#6 GolfSierra

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Posted 22 October 2012 - 10:03 PM

If the RA motor and worm are moving verify the N/S switch on the drive circuit board is set for north hemisphere operation. Remove the cover and you should see the switch next to the on/off switch on the main board.
The drive electronics are original? The 492 model electronics for a G11 and G8 look similar but have a different chip on the board with a sticker indicating 11 or 8.

Gary

#7 Dan Finnerty

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Posted 22 October 2012 - 10:12 PM

I have the G11/Gemini 2, so I can't help with the G1 unit. Thought it seems to me it has to be a setting of some sort. If you can slew the telescope in RA, the mechanics and motors are working.

Perhaps you can get some more serious help at the Yahoo Gemini-1 forum:

http://tech.groups.y...p/Gemini_Users/

#8 mdowns

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Posted 22 October 2012 - 10:57 PM

John,
The clutches are engaged. I thought about the drives getting reversed(N or S)but the switch for that is under the face plate of the control panel.It seems unlikely that the switch could have gotten changed (I wont rule that out though).

#9 Billydee

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Posted 22 October 2012 - 11:24 PM

You need to have a 12.6 volt 3 amp power supply to run a G-11. Each motor can pull .9 to 1.3 amps and if both slew at once you can get about 2.5 amp draw. If you have a 12.6 volt car battery you can try that. If you can hear the dec motor running and the mount does not move then you need to tighten the clutch.

Luck, Bill

#10 Retsub

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Posted 22 October 2012 - 11:35 PM

From your previous experience it seems like you have it balanced ok. Listen closely to the RA motor for the tickey, tickey, tickey sound. Should be able to hear it. Then set up faster the correction speed led's and press the RA button and it should sound faster or like said remove the small cover and look close at the shaft. ?? How much slack backlash does the end of the Dec shaft have in RA ? Wiggle it. A little is good. A lot or none is bad. Let us know. *BW*

#11 mdowns

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Posted 23 October 2012 - 05:37 AM

Billydee, This is a non-gemini model.Both motors never operate at the same time.The clutch is tight........

Retsub, Its got the 'little'wiggle.Next time out I'll remove the motor cover or at least listen for the change in speed.Thanks thus far for the replys,please keep them coming!

#12 mich_al

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Posted 23 October 2012 - 08:49 AM

I'm not a Losmandy guy but that power supply spec is definitely questionable, 500ma (1/2 amp) is not much current capability. I'd think a minimum of 5 amps would be needed. Radio Shack wouldn't be my first choice either. Pyramid makes good supplies and they are readily available used. I've bought off ebay with good results. Trying a car battery is a good suggestion though cabling could be an issue and you sure don't want to risk reverse polarity.

#13 SMigol

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Posted 23 October 2012 - 10:04 AM

Only thing that I can think of at the moment is if the mount isn't balanced well. If it's significantly imbalanced, these motors can slip when trying to lift the weight.

#14 Startraffic

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Posted 23 October 2012 - 11:24 AM

mdowns,
What you have there is a G11 with the digital Drive system & the optional encoders. It appears that you have the motor wires going to the correct motors.
Balance is critical, loosen the RA clutch completely, balance, tighten. Loosen the DEC clutch completely, balance, tighten. Recheck the RA & do a meridian flip, recheck the balance again. Repeat for the DEC until you can leave both axis's clutches completely loose and the OTA doesn't move. Snug the clutches up just enough that the begins tracking when you let go. The DDS is a push to & track. Push it to what to want to look at, get it in the EP then let it go, the DDS should pick up tracking. You want just enough tension on the clutch to hold the OTA in place against the wind or a light touch. It isn't like a GOTO where the clutches need to be TIGHT.
However if that little white thing on the leg it the power supply, that would be my guess. I tried one of those & found it couldn't quite run the mount. I found an older laptop power supply that had 12VDC output & the connector fit & used that. Works great, in fact I still use it as a backup power supply when I update my Gemini2.
The encoders you have on the RA & DEC axis' are for use with a computer like the Argo Navis (AN), or the SkyCommander (SC), and are digital setting circles. If they are indeed DSC's then hang on to them, Losmandy doesn't make them anymore, but they also work with the Gemini-1 system and will (once the code gets written) work with the Gemini-2. They allow you to pick a target with the AN/SC and push your scope to that target by reading the relative position of the RA & DEC axis'. It pretty slick actually. I put a SC on my G11 before I went GOTO. It never missed a beat, & I still have the encoders.
I would seriously recommend getting a set of Delrin Covers for them though. Those gears will chew through your wires, not to mention your skin. DAMHIKT.

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#15 mdowns

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Posted 23 October 2012 - 07:39 PM

Continued thanks to all for the replys.
Mich al The losmandy manuel for this one calls for a 12V.500ma power supply.Of course I have doubts about this one but it at least specs to what losmandy says.

Smigol and startraffic I did in fact balance the scope prior to use though I did have to shift the ota back abit when I put the scope on the moon. My intent right now is to rebalance and possibly try the weight shift trick either E or W.Perhaps I should first find another power supply though Mike Mix above commented that he uses the same model for his CG11 without trouble.This mount does have the DSCs,I just hav'nt hooked them up yet.Tracking is far more important to me right now.Unfortuneatly I came in late again tonight and so did'nt get to setup the unit.Mmmmm I do have an old laptop power supply as suggested,perhaps I'll try it. Again,thanks to all who have commented and please feel free to offer any suggestion.

#16 Ranger Tim

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Posted 23 October 2012 - 10:05 PM

Take the cover off of the RA worm to verify it is turning. This should rule out whether or not this is a clutch/balance problem. It will turn slowly so be patient. After a few minutes you will know whether the RA is tracking or not. If it is tracking/moving your clutch/balance is at fault. Re-balance and try again. After the balance is ruled out, break down the RA axis and check to see if there is lube leaking onto the clutch pads. Clean and reassemble. Take the time to admire the rest of the assembly while it is apart. Check the needle bearings for adequate lubrication. Clean and lube as necessary.

If the worm is not moving there is a power/motor problem. Check the connection at the motor and controller. Label the motor cables "a" and "b" (or RA and DEC) so that you can track their use. Switch them to check for a difference.

You say the hand control works to move the RA axis? So set the controller to its highest setting (16X?) and press the hand control button. Does the RA worm move faster? Check for looseness at the coupler between the motor and the worm. There is a set screw on this coupler device (two silver circles with nesting plastic things) that can come loose - it is a small SAE allen screw. There are two of the screws. If the motor is not moving you may not be able to turn the worm by hand to check them.

Check to make sure that the hand control sliders are not on reverse settings. The motor will make little "munching" sounds as it operates. Do you hear this? Finally, you can switch the motors and try again to rule out the motor as being the defective part. Don't worry about the worm backlash tolerances, you will need to learn how to set that yourself anyway. Just don't pull this thing apart without having a tarp or some way to catch small parts that might fall into the grass. Ask me how I know :tonofbricks:

#17 Hilmi

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Posted 24 October 2012 - 12:01 AM

Could be the gearbox to worm coupling not tightened. My brand new mount had that problem and I had to tighten it down.

#18 gezak22

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Posted 24 October 2012 - 12:29 AM

Could be the gearbox to worm coupling not tightened. My brand new mount had that problem and I had to tighten it down.


Seconded.

After regreasing my GM8, mine was no longer tracking either until I tightened the gearbox-to-worm screw.

#19 MPT

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Posted 24 October 2012 - 05:30 AM

Could be the gearbox to worm coupling not tightened. My brand new mount had that problem and I had to tighten it down.


Seconded.

After regreasing my GM8, mine was no longer tracking either until I tightened the gearbox-to-worm screw.


This is the same issue I had with mine as well. It was quite the odd issue as it would slew fine, but would not track. Apparently the higher torque and quick movement was enough for the worm to catch while slewing, but the tiny movement from tracking just left the motor turning and the worm stationary.

#20 Cotts

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Posted 24 October 2012 - 07:30 AM

Even when you solve this you need a much beefier power supply. 5 amps continuous. Also, have the power supply near to the mount as opposed to a long run from a wall socket. If you must run a long wire, run the 120volt AC a long way with a good quality, heavy gauge extension cord and the 12vdc only a few feet. Much less power loss that way.
And, finally, those plug into the wall transformers are not near the quality in terms of voltage regulation and smoothness compared to a proper power supply like this....

http://www.pyramidca...mp-Power-Supply

Available at Ham Radio Stores, electronics supply houses etc....

Dave

#21 Raginar

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Posted 24 October 2012 - 07:49 AM

Perhaps a call to Scott would help you out. From what I've read, the Losmandy guys are awesome about taking phone calls.

My guess would be the power supply as well. You'll know when you remove the RA gear cover and see if it's tracking.

#22 Ranger Tim

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Posted 24 October 2012 - 09:36 AM

There is no gearbox on the digital drive, just Hurst motors. But the same advice applies, check the coupler set screws for tightness on both the worm and the motor shaft.

#23 Startraffic

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Posted 24 October 2012 - 12:41 PM

Hilmi,
I had forgotten about that, & that could indeed be the trouble.

Dave,
Yup, I've got a 0-20 VDC 20A Pyramid in my POD. I set it at 18VDC for the Gemini-2. The 120VAC run from the house is ~100ft wi 12 Ga wire, the run from the PS to the mount 2 ft on 4 ga wire.

Clear Dark Skies
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#24 mdowns

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Posted 24 October 2012 - 09:11 PM

Problem identified,almost solved.

Many thanks to all who have replied.I did indeed call Scott at losmandy and he told me that first,the 12V,.500 amp power supply is indeed adequate for the mount.Then he suggested that I had either reversed the ra/dec connections,that the drive had been switched from N to S or I was having a balance issue. All much the same as so many of you had already suggested.Well I knew that the drive orientation had not switched so I first reversed the drive connections.This did'nt remedy the problem. Finally tonight I took the scope very slightly out of balance.After an intial shift of about half an inch to an inch of the counterweights I began adjusting them in increments of just a few millimeters.Over the course of twenty minutes of ever so slightly shifting the weights I got tracking.I've owned more gems than I can really recall including a gm8 but have never had a mount so extremely sensitive to weight.Several commentors here as well as the cnighter I bought this from had suggested this concern.I should have been more open minded.You guys were right! Tracking is not yet perfect,probably shifting a few more mils and I'll have it :-) Heres a pic of the final weight setting before I called it a night.....

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#25 mdowns

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Posted 24 October 2012 - 09:15 PM

The air was really boiling,not allowing anything clear over 100x or so but i took a few test images with my point and shoot. Here's one.....

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