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Last time I used my Losmandy G11/Gemini-1, it kept giving "Motor Stalled" message when starting go-to alignment. I came to believe the problem was with the Dec motor/gear train.?

So yesterday during daylight hours, I had an opportunity to service the declination worm-gear set. I was able to tip the worm away from the worm-gear (ring-gear) without disconnecting from the drive motor. This allowed for cleaning the ring-gear of any debris that might be causing the motor to stall. An old toothbrush was used to clean each gear tooth and more uniformly distribute the lubricating grease. I see the need for a more thorough cleaning, to remove old grease and apply fresh lube. But for now I have done a quick service.

?

I used the opportunity to set the gear clearance for minimum free-play and backlash. Even though I could move the worm by hand with no resistance, upon tuning on the Losmandy G-11 electronics, I still got a "motor-stalled" warning. So I restarted and bypassed go-to alignment. Then selecting the "Sidereal" drive rate, I was able to use the hand controller to move both RA and Dec without motor stall error. Then restarting the electronics allowed for normal go-to alignment, without motor-stall errors. This led me to believe the problem was not mechanical - that is detritus where the gears meshed causing the stall. It appeared the problem was electrical or software. Now I'm hoping the mount will function properly under nighttime conditions.

Any comments, suggestions or advice would be appreciated.

Russ

Last time I used my Losmandy G11/Gemini-1, it kept giving "Motor Stalled" message when starting go-to alignment. I came to believe the problem was with the Dec motor/gear train.?

So yesterday during daylight hours, I had an opportunity to service the declination worm-gear set. I was able to tip the worm away from the worm-gear (ring-gear) without disconnecting from the drive motor. This allowed for cleaning the ring-gear of any debris that might be causing the motor to stall. An old toothbrush was used to clean each gear tooth and more uniformly distribute the lubricating grease. I see the need for a more thorough cleaning, to remove old grease and apply fresh lube. But for now I have done a quick service.

?

I used the opportunity to set the gear clearance for minimum free-play and backlash. Even though I could move the worm by hand with no resistance, upon tuning on the Losmandy G-11 electronics, I still got a "motor-stalled" warning. So I restarted and bypassed go-to alignment. Then selecting the "Sidereal" drive rate, I was able to use the hand controller to move both RA and Dec without motor stall error. Then restarting the electronics allowed for normal go-to alignment, without motor-stall errors. This led me to believe the problem was not mechanical - that is detritus where the gears meshed causing the stall. It appeared the problem was electrical or software. Now I'm hoping the mount will function properly under nighttime conditions.

Any comments, suggestions or advice would be appreciated.

Russ

On 1/24/2021 4:17 PM, Michael Herman wrote:
> Russ,
>
> A few things can cause this behavior.
> First of all, check the motor cable both ends for any corrosion of the 6
> pins at each end.? I try to polish those connection pins up.
> Likewise the female pin contacts inside the connectors could be
> oxidized.? You might be able to put a thin round (rat-tail) file in and
> make the contacts better.
>
> So try that first.

I would be VERY careful using a file.? Most contacts are plated and
using a file on them will very likely remove some plating.? This can
expose the underlying base metal which will then corrode, making things
worse long term.

Paul

--
Paul Goelz
Rochester Hills, MI? USA
pgoelz@...

Good suggestion! That sounds safer and more effective than mechanically removing oxidation. I remember having a spray can of Radio Shack contact clean somewhere. If I can find that, I'll give it a try. Otherwise I'll get some DeOxit. It claims to be protective of the contact surfaces. In the moist environment that would be a plus.

Russ

[Edited Message Follows]

Thanks, Brian. My supply is a Pyramid 5-amp (7-amp surge), 12-volt supply set for 13.8 volts. I'll look into whether there is a voltage set adjustment internally for a higher input to the mount's electronics. I use power pole connectors between power supply and the Gemini power input cable. But all other connections are via push-in multi-pin connectors. As was mentioned, these can be subject to corrosion or detritus interfering with good, low drop connection.

When I bypassed initial star alignment, I chose sidereal to enable the hand controller to control motors directly. Once I got the Dec motor to respond, the motor-stall error went away on go-to star alignment.

Edit:
I checked the supply voltage - 13.8V idle, 13.6V under light load. I used a small inverter to power a <10W LED lamp. So upping the output voltage looks to be worthwhile. I don't use it for anything but the Losmandy G11 mount.

Russ

Thanks, Michael. I'll give all of your suggestions some attention. I determined that my power supply doesn't have a voltage adjustment inside the chassis. So 13.8 volts it is. Reducing slew speed and making sure motor, cable and Gemini contacts are as clean as possible will be a good place to focus. I'll look into tweaking the female contacts for best low-drop connection. Right now all is on hold waiting for a clear night. Today was another hosing with the "atmospheric river" of rain.?

If I get too bored I have over 20 Mars videos still to process. These were gathered with the C-11 just after closest approach.?

Take care,
Russ

Hi Michael,

With Spring to soon be upon us, I would be very surprised if I was able to get to very many of the Mars videos. I've got fruit trees to prune and birdhouses to clean. And garden planting will be starting soon. But if it rains all spring like it did one year when I was in Eureka, CA, I may get to more of them. With Mars having such a slow apparent rotation, even within a 2 minute video I don't know how much use Winjupos would be. But it might be good to become familiar with it for when Jupiter is back in easy viewing.

I had a go at using the G-11 last night. Using spray contact cleaner I had cleaned all the motor cable pins and sockets, along with DC and motor sockets on the Gemini chassis. When I last used the mount (without telescope or counterweight shaft), it seemed to work OK. But alas under the stars it kept giving "motor stalled" errors. I flipped both motor cables end for end to see if being flexed differently would fix any breaks that might have happened. Still no go. I was unable to bypass alignment menu and choose sidereal mode with hand paddle moving motors via that means. Before, that was what cleared the "motor stalled" error. In sidereal drive mode, the motors were unresponsive. By sidereal mode, I mean pressing the menu button to toggle between menu items or motor control by the 4 buttons.

But after numerous power off/on and alignment re-tries the error persisted. Then I noticed I could hear one motor (not sure which one) would start to move, then stall. So I made another attempt with my ear up against the RA motor to see if that was the problem. And success! - ?it slewed to the first alignment star without stalling. It functioned without error after that, going to several alignment stars without stalling. So I'm thinking the problem is with the RA motor. When my ear was against the motor (to hear if it quickly stalled on startup), perhaps I had given a bit of mechanical pressure. So the investigation continues.

Next I will be following your suggestion of tweaking the contacts inside the female sockets to get a more solid connection. Also reducing maximum slew speed may be what is needed. Thanks for your suggestions, Michael!

Best Regards,
Russ