Kon

12 hours ago, Cosmic Geoff said:

While I have not examined one of these mounts, I am surprised that the azimuth motor should have developed significant bearing wear. My experience of small motors is that this doesn't happen.  If it has, one might expect that under load it would fail to engage with the gearbox at all.   If it IS a motor fault, getting another might prove troublesome and if you can't definitely identify it as a generic motor you can buy on Ebay or from China, your only other recourse is to buy another subassembly or scrap mount.  Or find a craftsman prepared to fit another bearing bush to your motor.

A useful means of diagnostic where the altitude and azimuth drives (etc) have similar parts is to swap bits over and see if the fault follows the part.   The altitude  and azimuth motor/gearboxes in the Celestron SLT mount are the same (same part number) and I swapped them over while chasing a fault. (It wasn't in the motors).

If you attach tell-tales (bits of paper or magic marker marks) to slow moving parts, you can see if anything is moving (slowly) or not.

Thanks for the suggestions Geoff. I swapped the encoder and gears and the problem persisted. I didn't swap the motor but I noticed that the shaft of the azimuth motor has a lot of play, going back forwards when I press it. The alt one doesn't seem to have it. I also noticed the az makes a squeaky noise (even without gears) whereas the alt is quite, thus why I thought it is the motor. If the PCB has a fault I would expect the motor control to be dead? The wormwheel and brass turn extremely slowly but no transfer of movement to the large disc so the motor is engaging with the gears ok. I checked and tightened for slippage. I am running out of ideas what to check next.

It seems that I need a new motor replacement for my Skywatcher 300P goto.  It is the azimuth and it appears to be the output shaft having quite a bit of play and therefore I have lost tracking. Finding replacements from skywatcher are not easy.  Any ideas if I can source a motor where I can add the current encoder or have you had luck getting motors from skywatcher directly? Or do you know what motors these goto have (voltage and rpm?)  I have not seen anything at FLO. Motor below with the gears etc off.

I looked at both axis motors and it seems the az motor is faulty; no electrical but the output shaft has a lot of play compared to the alt. It seems I need to source a new one.

Marco Campaniello is very talented individual who took my Maurolycus crater capture from 15/04/24, and converted it to a 3d fly over using real moon topological data. Do not ask me the details but do have a look at his youtube video that has more of these conversions with amateur captures.

Any my image for reference that allows to move it in 3d:

http://moon3d.altervista.org/maurolycus_3d/maurolycus.html

Original image:

1 hour ago, dweller25 said:

Yes, if you can track it fast enough - it moves very quickly, but @Kon manages it with a dobsonian…….

https://stargazerslounge.com/topic/418411-first-international-space-station-for-2024-260124/#comment-4453699

 

To be honest I have never seen it through an eyepiece, guilty I know, as my efforts have been on imaging it; my only live view is through the finderscope and you can make the panels. I think @PeterStudzhas seen it through an 8" with manual tracking.

Nice images. The mineral colours subtle and excellent.

Nice one Reggie.

13 hours ago, michael8554 said:

Can you swap with the Alt motor ?

So I swapped the encoder and the problem persists; if it is the correct part (the green chip in this photo). I did not want to mess more with the Alt as it is tracking very well. It seems to be a faulty motor. I will look into sourcing a new one (I have not found anything yet). I might start a new post for a motor 🥲

40 minutes ago, michael8554 said:

Have you tried with a better power supply yet ?

But Geoff mentions that this is a stepper motor.

Skywatcher describe it as a "DC Servo motor".

As I understand it, a DC Servo motor only has a single pulse drive and feedback loop from the encoder, unlike a stepper motor, which has two phased inputs.

Could be wrong.

Although a pulsed signal, you might compare the voltages with a cheap Digital Voltmeter at slew and tracking rates.

Can you swap with the Alt motor ?

Michael

I am not an electronics expert, so looking online it was described as stepper but I could well be wrong.

I thought of swapping the motors around but as my Alt is perfect, do I mess with it? But it will be a good diagnostic.

Yes I changed the power supply, not as fancy as the one you suggested but I will invest on very good one.

A voltmeter would be good. I assume I should have similar power?

The current diagnostics are that removing the cable from the board to the stepper the motor runs fast; with the cable back on it's running at low speed as expected. I suppose it rules out a faulty stepper. Unless it's not giving enough torque, partly faulty?

I tightened the central bolt to the point that it was very firm base but no tracking.

What I can't get my head around is, why the wormwheel and brass turn but not the large metal disc. Where else should I be looking? I took the whole clutch system off to check but nothing. 

Any other suggestions?

21 minutes ago, Jim L said:

How is the balance of the scope? The clutch can only lift so much, and heavy eyepieces, etc., might be too much for it to handle. If that’s the case, a counterweight on the lower half of the scope might be the solution.

Balance is ok. I had no issues tracking for the past 3 months I had it and it just stop tracking at the azimuth.

48 minutes ago, Geoff Lister said:

Some years ago, with my 250PX, I had problems with slewing and tracking in the Az axis. It turned out to be one of the encoder ribbon cable connectors adrift from its position on the control board's pins. The ribbon cable layout may have been defined before the ferrite rings had been added (probably to pass regulatory EMC tests) and there was little slack in the cables. It was difficult to spot the poor connection, as it was under the control board. The problems went away once I had re-seated the plug, and has been fine since.

The clutch friction is a compromise between (1) good motor drive, and (2) manual operation without using the handset.

Geoff

 

In these photos, what I am looking for?

2 hours ago, Peter Drew said:

It probably needs at least some grease as the clutch has to be able to slip in the event of something impeding the rotation.  The "trick" is to adjust the slippage torque to avoid slippage in normal use but also to avoid locking up.  Try tightening the nut a small amount.     🙂    

Thanks. It seems that I have lost torque to turn the wormwheel and brass when 'tracking' although at higher speed it works; this is with no clutch and large wheel?. Hmmm

After shutting down and restarting it turns with and without the wheel?? Most peculiar 

1 hour ago, bosun21 said:

Have you tried moving it with the HC at the various speeds? Perhaps slippage could occur at slow rates 1-3.

2+3 seem to work.

6 minutes ago, Peter Drew said:

If the brass worm is turning then the wormwheel must also be turning which points to clutch slip as already diagnosed.      🙂

I opened up last night and it all looks ok. One thing I noticed is that there was a lot of grease on the small  spacers just under the big nut. Would that be causing it? Do they need the grease?

So why at high speed with the controller is it ok to turn?

1. I opened up the azimuth motor compartment and check everything for slipping. I could see wormwheel running fine It didn't solve the problems.

2. I opened the gear box, all ok. It didn't solve the problem.

3. The motor itself seems to function ok but could it be something to do with the encoder? I can see the wormwheel running but the large disc or platform is not turning. It can turn with the hand controller. So if it is not slipping is it likely the stepper does not provide enough torque? Ie is it gone?

Thoughts on a replacement for it, assuming it's the culprit?

Rupes Recta looked spectacular last night; Rima Berta was also nicely visible. I did some imaging after observing. 12" Dob Flextube, goto, asi462mm, IR pass 685nm, 2.5x TV powermate.

7 minutes ago, Clarkey said:

Found this online for a 14" Orion. Does not solve your problem as such, but it does show the whole assembly being dismantled. The motor appears to be spring loaded.

 

Perfect, thanks. I was looking for something like this. It gives me confidence to properly open it up now and see what is going on.

10 minutes ago, Clarkey said:

If the Dobs are anything like the 'normal' skywatcher mounts then the meshing between the drive wheel and the worm could be a touch tight. This is then causing the motor to stall - hence the rough sounds. On the standard mounts the worm can be adjusted in and out (mainly to allow for poor manufacturing tolerances). I'm not sure if this is possible on the Dob? Is the whole motor /gear/worm assembly moveable?

Hard to tell if it is movable but I see a black screw at 6 oclcok in my photo that is adjusted to a sping, I wonder if that has to do with tolerance? It will be some investigating job tonight.

11 minutes ago, Carbon Brush said:

Going back to the original report, the worm is turning, which suggests clutch slip.
Driving at high speed might overcome some of the slip.

A good test is to remove the scope tube and just leave a flag (bit of paper) on the mount and see if it tracks.
If all is well on light load, you have a slipping clutch.

Skywatcher clutches are not the best in the world.
If the clutch is slipping, tighten the nut by a small amount. Say 1/10 turn and see what happens.

I would also get rid of the small (uknown origin) plug top PSU.
Put a decent supply (like a Nevada) on there and you know you have a good supply.
Explaining why an unknown and under-rated PSU is risking problems requires more than a one line answer🙂

HTH, David.

Thansk for the suggestions. Michael suggested similar thing, but without the tube I do not see any tracking either, unless the nut is undone more than i thought so it is completely slipping.

I will definitely look into getting a a new power supply.

6 minutes ago, michael8554 said:

"I am powering from the mains."

But how ?

The spec is "11 to 15V @ 2amp."

Users are recommending 13.8V @ 5Amp.

And it needs to be a Regulated power supply.

Michael

 

I bought it second hand, and it came with a mains adaptor (12V 0.9A), I assumed from Skywatcher (from manual: 10 to 15 V DC 1Amp), plugged to the mains. But why tracking ok for the past couple of months if it was a power issue?

1 minute ago, michael8554 said:

1.  "Yes correct, the motors seem to be fine."

You don't agree the clutch is okay ?

2.  "I can hear the motor trying to track"

Perhaps the motor has enough oomph to start a high-speed slew.

But not enough to overcome the friction of the system, bearings etc,  when tracking.

Are you able to remove the motor and worm assembly, and check the worm runs quietly without a load ?

And that the wormwheel rotates freely without binding or much resistance ?

What power supply ?

Michael

 

 

Yes clutch too, sorry.

I am powering from the mains. It's a bit odd as it was tracking ok and I stopped to have a break and when i went back it wouldn't. I could try undo the nut and take the wormwheel off and see if the motor still makes the noise.

4 minutes ago, michael8554 said:

If the mount slews in Az with the hand controller, then the clutch and motor must be working - right ?

Yes correct, the motors seem to be fine.

4 minutes ago, michael8554 said:

s it tracking in Az as setup in the image ?

Put a finger mark in the grease on the wormwheel adjacent to the worm, and check that the wormwheel has moved after 10 minutes.

I just opened the housing and yes I did do this test last night but no movement. I can hear the motor trying to track, there is some noise (when it was tracking ok it was quietter, more like a humming noise). It is more of rougher sound now; not loud, i need to be close to the base to hear it..

During my imaging last night, the AZ motor of my 12" Syncan GOTO stopped tracking; I could hear the motor working but not tracking and I could use the hand controller to move the telescope so the motor is operating ok. Is it just slipping? The clutch was tighten and I had no issues until last night with it.  I opened the housing but I am lost beyond that. The brass rode is rotating with the controller. I can see another black disk under the whole system.  I found some info online that I could tighten the nut at the top. Before I do anything silly, are there any suggestions?

Nice images. Rupes Recta has an almost 3d feeling to it in the last image.