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Meade DS-2000 Motor Unit Fault

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#1 Jacs532

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Posted 12 February 2019 - 07:46 AM

Hello, I've been searching the net high and low but not managing.

 

I have a Meade DS-2114 telescope. I have read to manual back to front but haven't gotten anywhere.

 

When attempting to move the telescope with the autostar in the horizontal direction (either left or right) the motors engage but after give or take 5 seconds they stop and on the screen a message appears saying a motor unit fault has occurred. The vertical motor has no issues and always moves all the way when engaging it.

 

I have seen some threads where they recommend (if you are comfortable with it) to open up the base and clean off any grease which may be on the  encoder. So I opened it up carefully and saw the encoder (I think) and wiped it with a soft cloth, not that there was any residue on it. I assembled it all again, did a reset but the same happened. I have also done a motor calibration from the setup menu.

 

Any advice?



#2 Messierthanwhat

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Posted 12 February 2019 - 08:27 AM

First thing to check is your power supply. How are you powering the mount? By far the most common cause the Autostar "motor unit fault" is power that drops below required voltage during movement. The problem first occurs with the azimuth motor because that's the axis that moves the entire load of the mount and OTA, but doesn't benefit from balance as the altitude motor does. 



#3 Geo.

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Posted 12 February 2019 - 09:33 AM

Or the drive isn't communicating with the hand controller due to a fault in the signal connections, Check the cabling for loose/corroded connections or breaks in the wires.



#4 OzAndrewJ

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Posted 12 February 2019 - 03:39 PM

Gday George

The fact the Az drive starts on request then fails indicates its comms are probably OK.

"Motor Fault" occurs immediately during booting if the Hbx can't talk to the RA card.

The fact he doesnt get a "Motor Fault" on booting, but gets a "Motor UNIT fault" on starting to slew, normally means the motorcards are working, but the encoder feedback loop is not working properly.

If you have a webcam or DSLR in live mode, use it to look at the LED when energised.

The LED is InfraRed and you can see if it is working that way.

Andrew Johansen Melbourne Australia



#5 Jacs532

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Posted 13 February 2019 - 12:50 AM

First thing to check is your power supply. How are you powering the mount? By far the most common cause the Autostar "motor unit fault" is power that drops below required voltage during movement. The problem first occurs with the azimuth motor because that's the axis that moves the entire load of the mount and OTA, but doesn't benefit from balance as the altitude motor does. 

At the moment it is still powered by the battery pack ( 8x AA Energizer 1.5 V batteries). They are brand new, but maybe I should investigate other battery options, or even the conversion and leave the batteries behind altogether. Thanks



#6 Jacs532

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Posted 17 February 2019 - 05:25 AM

I have an update on the situation, with more questions. . .

 

I converted the power supply to a 12V battery but I still get the motor unit fault. Initially, while trying to do a two-star alignment the motor kept going for a longer period of time but then the same thing happened.

 

I have opened up the mount again and checked what I believe to be the encoder on the motor, and took some pictures. If I am looking at the correct things, I didn't see any LED light up through a camera. On the image, I looked at both the 'white transparent' one as well as the darker one on the left which are placed below the big white gear coming from the motor.

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#7 Jacs532

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Posted 17 February 2019 - 05:38 AM

Just trying to document as much of what is happening.

 

When I press GOTO, and for example select the star Sirius, the motors engage and run for approximately 10 seconds. But while this is happening it sounds like the Az. motors are sort of 'stuttering' if that makes sense?

 

Quickly after that, I get the same motor unit fault message. I then have to press MODE and a message displays saying "Testing motors". The Alt. motor test runs, moving it slightly, then the Az. motor runs moving it slightly. No message displays saying complete, the system reboots, and I have t enter the date and time again.

 

Another fact I should mention is that the telescope stood stationary for at least 7 or 8 years since it was last used. . .

 

Previously there were no issues while using the mount with the 8x AA batteries.



#8 Geo.

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Posted 11 March 2019 - 11:48 AM

Well, the part of the encoder that is clear plastic is the emitter. It should be illuminated as long as the power is on as it's connected to VCC.

 

This is the DS LED circuit the DS2K is similar but may have fewer resistors.

 

DS-LED.jpg

 

As you can see the current flows into the LED and then to ground through the microprocessor. The path to ground, ports RB2-RB7 is selected during the calibration routine. LEDs are pretty reliable. Note the orientation of the lens molded on the face of the LED that face should illuminate the receiver. Pull the LED out of its connector if it is socketed and reseat it. Test for illumination. 

 

If that fails test for power at the LED. If you have power then the LED may have failed. Let me know and I can send you a spare.

 

 


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#9 OzAndrewJ

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Posted 11 March 2019 - 03:33 PM

Gday Jacs532

George has it covered. The clear device should be emitting IR light when powered, and you should be able to see that using a DSLR or webcam.

When you do a calibrate, the PIC toggles the row of resistors on/off to adjust the current going through it

ie as George noted, it should always be ON if the board is powered.

If you have a multimeter, measure the voltage drop across the unit to ensure it is getting power

 

Andrew Johansen Melbourne Australia



#10 Geo.

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Posted 12 March 2019 - 08:53 AM

God is in the conductors. The Devil is in the connectors! Well, most of the time=8)



#11 Jacs532

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Posted 16 March 2019 - 11:27 AM

Well, the part of the encoder that is clear plastic is the emitter. It should be illuminated as long as the power is on as it's connected to VCC.

 

This is the DS LED circuit the DS2K is similar but may have fewer resistors.

 

attachicon.gif DS-LED.jpg

 

As you can see the current flows into the LED and then to ground through the microprocessor. The path to ground, ports RB2-RB7 is selected during the calibration routine. LEDs are pretty reliable. Note the orientation of the lens molded on the face of the LED that face should illuminate the receiver. Pull the LED out of its connector if it is socketed and reseat it. Test for illumination. 

 

If that fails test for power at the LED. If you have power then the LED may have failed. Let me know and I can send you a spare.

Hello Geo.

 

I ran the test you suggested, and got the following results:

 

I removed the LED from the holder and tested it with a multimeter on the Diode setting and got a reading of 1202. Also, I tested power to the diode along the wires, and I believe there is indeed power there.

 

when I look at the LED through a camera device, I don't see any activity. So that would mean that it is not working correctly?

When I reseated the whole assembly, still got the same fault.

What else can I do? or is it best to just replace the LED?

On one side of the encoder wheel there is this LED and on the other side, a black shiny sensor, could this have blown as well? Would you suggest replacing both at the same time?



#12 AstroChampion

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Posted 30 July 2019 - 09:29 PM

I’m not original poster but I accidentally reversed polarity for less than 1 second and now it won’t go past motor fault message.  Any ideas for me?



#13 unn

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Posted 09 October 2019 - 07:28 PM

I realize this thread is a few months old however I hope I can get an answer.

 

Hello OZAndrew and Geo,

 

I have same problem with my DS2000 mount. It has been giving "motor unit fault". I opened it. Swapped the clear LED from the upper motor with one from another DS2000. Well, with that the unit now works. No more fault. When I tested the bad LED with multi-meter, it reads 1100 forward and nothing backwards. What does 1100 mean? Ohms or something else?

 

Question: I want to replace the good one I took out. what are the technical specifications for this emitter LED and where do I buy it in USA (what type of store)? This one is a flat / square shape. The ones I have seen in various web shops are round dome shaped. Meade is not helpful. They said "we do not support this model any more. Besides we don't repair any thing, we just replace it with new parts".

 

Thanks for the help.



#14 OzAndrewJ

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Posted 09 October 2019 - 07:53 PM

Gday unn

 

Normal diode testers measure the forward voltage drop across the internal junction,

but i dont know if that works with LEDs.

Normally, i just measure the voltage drop across the LED when in circuit with proper current control.

When OK, you will normally see a 1.2-1.5v drop across the unit.

 

As noted earlier, You can also test if they are working using a DSLR or webcam, as they show up quite well.

 

As to specs, all i know is it is an infra red LED

and where to buy in small quantities, i have no idea

Maybe someone with a damaged/burnt out board will sell one for spares????

else google is your friend

 

Andrew Johansen Melbourne Australia



#15 unn

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Posted 11 October 2019 - 05:17 PM

Thank you OZ.

 

I fixed it. I happened to notice that the color of the wires leading from the LED were reversed on the "bad LED". I hooked it up in reverse and it worked fine. Thank you.



#16 OzAndrewJ

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Posted 11 October 2019 - 05:42 PM

Gday unn

Excellent news, but it begs the question why it didnt work before???

Maybe just an oxidised connection??

 

Andrew Johansen Melbourne Australia



#17 Geo.

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Posted 27 October 2019 - 03:33 PM

Reversed DMM current current through an LED will show as an open circuit like any other diode. Reversed VCC will sometimes blow an LED.


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#18 Skywatchr

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Posted 29 October 2019 - 11:28 AM

Reversed DMM current current through an LED will show as an open circuit like any other diode. Reversed VCC will sometimes blow an LED.

Exactly. An LED *is* a diode that just happens to emit light by design. Hence the name, L)ight E)mitting D)iode. And in some circuits, it's not just a "lamp", it's also an integral part of the circuit where a particular voltage drop, and/or reverse current limit is necessary to operate the circuit.




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