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CG5 declination motor just stopped working!

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#26 RobbW

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Posted 22 August 2012 - 12:05 AM

All the small, inexpensive parts I ordered came in today. I completely set up my scope assembly this time including mount, tripod, OTA, and counterweights. I wanted to test if the DEC motor was simply wearing out and couldn't handle the full load anymore. Unfortunately, the DEC motor wouldn't work with or without the full load. So, it seems it was completely gone this time and had nothing to do with the weight of my scope and gear on the mount.

I proceeded to take all the plastic covers off the mount to perform more test before I started swapping out parts. I checked to make sure the RA motor still worked fine, which it did. I then disconnected the RA motor's wire connector from the Motor Control Board (MCB)and attached the DEC motor's wire connector in its place. Pressing the slew buttons on the hand control, I still could not get the DEC motor to operate. Connected the RA motor back up to the MCB, and it worked fine again. So, this is definitely making me lean more toward it being an issue with the DEC motor than with any of the control or power boards.

However, before I resort to ordering a new DEC motor, I want to replace the DEC port and Power Board with the new ones I bought, just to be sure. So, I swapped out those parts and hooked everything back up. Still, the DEC motor would not turn.

I then decided to start fiddling with all the wires to see if it was a damaged wire. While continuously holding down the North slew button, I started jiggling all the wire connections and bending all the wires. Nothing happened. Then I unplugged the encoder wire connector from the bottom of the DEC motor and plugged it back in. Suddenly, I got a very brief but very fast slew from the DEC motor. And then I got the "No Response 17" error on the Hand Control.

I powered the mount off and back on again to clear the error message. Tried slewing the DEC motor again and the same thing happened. Very fast but short movement from the DEC motor followed by the "No Response 17" message. I powered off/on my mount again, and this time I removed the cap from the encoder wheel on the bottom of the DEC motor. After removing the cap, I was able to continuously slew the DEC motor.

However, something was definitely wrong with it. The slew rate was exceptionally fast. Much faster than I'd ever seen it before, and the motor was extremely loud. I tried adjusting the slew rate from 9 down to 5, but the DEC motor still moved at the same ultra-fast speed regardless of what slew rate I set. The RA motor operated at the correct speed for whatever slew rate I set, but the DEC motor stayed in afterburner mode. Not only that, but the DEC motor wouldn't stop immediately after I let go of the slew button. It would continue to slew for 2-3 seconds before finally stopping.

I put the cap back on the encoder wheel and kept fiddling with its wire connection to see if that was the culprit. Unfortunately, messing with the wires didn't seem to affect anything. After running the DEC motor in this super fast rate for a bit, it started throwing up the "No Response 17" error again. I could press "UNDO" to clear the error, but then the DEC motor wouldn't work anymore. The RA motor still worked perfectly fine this entire time. After power cycling the mount again, the DEC motor is now giving the "No Response 17" error pretty much every time and is only operating in the super-fast slew rate intermittently (maybe once in every 3-4 tries after power cycling).

After messing with this for about 1.5 hours, I gave up. I cleaned up all my parts and put my mount back together. I resolved to simply order a new DEC motor as everything I tested out seems to point to it being the problem.

I placed my order with Celestron tonight and will patiently (or not) await its delivery. I can only hope that the new DEC motor will finally clear away all my problems, and I can have a properly working CG5 mount again.

Keeping my fingers crossed!

#27 RTLR 12

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Posted 22 August 2012 - 02:35 AM

Did you check the air gap on the encoder wheel? The air gap between the optical pick up on the encoder and the surface of the encoder wheel should be set at about .035" to .045". Be very careful when setting or measuring the air gap as the encoder wheel is made of glass and is fragile.

Stan

#28 RobbW

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Posted 22 August 2012 - 12:58 PM

No, I did not, Stan. I have no tools for making small measurements like that. Besides, I've fooled around with this thing long enough for my liking. I just went ahead and ordered a new DEC motor. When it comes in, I will install it and hope that all my issues go away!

#29 RobbW

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Posted 28 August 2012 - 10:30 PM

New DEC motor arrived via UPS today. After the kids went to bed, I took the covers off my mount and replaced the motor. The difference and improvement in its performance was immediately obvious. I put the covers back on and loaded the mount up with OTA and counterweights. After 30 minutes of testing, everything is whirring like clockwork!

Turns out there is one small problem though. When I was disassembling my scope and moving everything out of my kitchen, I found my power supply to be leaking an unknown liquid. Closer inspection revealed it to be sulfuric acid leaking out of the battery. Yeesh! Another part needing replacement!

#30 RobbW

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Posted 31 August 2012 - 05:49 PM

UPS says replacement parts should be delivered this coming Tuesday. So, now my question is: does ordering mundane, internal repair parts invoke the astronomy curse? I would hope not. It's not like this is some new EP or other astro toy that I'm really excited to get. I'm just trying to fix my broken mount!


Ordering the parts doesn't. Getting the mount fixed an working does. :smirk:


I apologize to everyone for fixing my mount and replacing the battery in my power supply. I had no idea it would result in Issac socking us in for the whole weekend!

#31 ptsouth97

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Posted 24 October 2012 - 07:49 PM

My CG-5's declination motor stopped working, as well. After reading through this thread, I took the plastic casing off of the RA and declination drives and started poking around. At this point, I was still able to run the RA drive. Then, everything stopped working. I quickly realized that the red light on the power cord from my Celestron Power tank was no longer glowing. I disassembled it and found a blown fuse. I took a trip to an auto part shop and bought a 5 pack of replacement fuses. I popped a new one in and tested it for continuity and everything was fine. However, as soon as I plugged it into the scope, the fuse blew again. Any ideas here? If something is making contact and shorting out somewhere, I sure don't see it.

Thanks,
Blake

#32 RTLR 12

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Posted 24 October 2012 - 09:51 PM

Check the wires to the motor. They have been known to rub on the motor cases and short out.

Stan

#33 jchoy46

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Posted 25 October 2012 - 07:24 AM

also stop using the on/ off switch... they have gremlins and short out the scope!

#34 ptsouth97

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Posted 25 October 2012 - 07:30 AM

Thanks for the suggestion. Visually, the wires look ok and the connections seem tight. I'm showing a closed circuit from the motor board to the motors with a continuity test. Every time I put a new fuse into my power cord from the power tank, it blows almost instantly. I have power tanks/power cords and the same thing happens to both. Any other ideas?

#35 ptsouth97

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Posted 25 October 2012 - 07:31 AM

By stop using, I assume you mean just leave it on? I can handle that but would need an explanation for anything more complicated.

#36 ptsouth97

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Posted 25 October 2012 - 07:44 AM

I just tried replacing the fuse and plugging in the power cord to the power board with the power switch on. Same result: blown fuse immediately.

#37 rmollise

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Posted 25 October 2012 - 08:02 AM

By "closed circuit," you mean a dead short? For starters, examine the circuit board for any signs of burned components.

#38 ptsouth97

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Posted 25 October 2012 - 11:36 AM

Sorry if I'm using the wrong terminology as I'm new to this. When I said closed circuit, I was just saying I put the leads from the continuity tester on both sides of a particular element and the bulb on the tester lit up. I thought that meant the current was flowing through so the circuit was "closed."

I don't see anything on the circuit board that looks burned. How obvious should it be? One thing I noticed is that some of the wires have a slight yellow discoloration to them. However, again, I'm showing that they are still working with the continuity test. Maybe I'm doing something wrong?

#39 rmollise

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Posted 25 October 2012 - 01:52 PM

What I would advise, other than the usual...check can clean all connections, is have a buddy with some electronics experience check things out. If you are getting continuity between an input and an output on the PCB, something is badly wrong (unless what you are checking chassis ground or something...

#40 jchoy46

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Posted 26 October 2012 - 09:05 AM

i just leave the switch on and unplug the power cord to turn it off and when i want to use it, i just plug it in. CG%'s have a known bug with the power switches. So I dont use mine.

#41 ptsouth97

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Posted 27 October 2012 - 10:04 AM

Yeah, that's what I tried. I ordered a new power board and hopefully that will do the trick.

#42 ptsouth97

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Posted 05 November 2012 - 03:19 PM

So the new power board arrived and I swapped it out with the old one. The fuse blew again in about 1 second and this time I got the tell-tale plume of smoke and smell of crispy circuits. There was no such indication of burning on the old power board. Assuming the new board was ok to begin with, am I looking at a problem with the power cord running from the battery to the mount? I was reading on another thread that the Celestron cords can be faulty and can be replaced by one from Radioshack. I don't think it's the battery,because the battery is supplying power just fine to my Nexstar 4se.

#43 rmollise

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Posted 05 November 2012 - 03:55 PM

If you can't do so yourself, find a buddy with electronics/electrical experience and have him/her check your cable, connectors, etc.

#44 nebultick

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Posted 06 November 2012 - 11:53 AM

probably completely unrelated but if this happens to anyone else. My dec motor on my super polaris started to die while imaging last night. I used a battery pack with 8 D cells. Well they were dead, the RA motor would still move just fine but the Dec would be all kinds of funky. I hooked up it to a 12V supply and it worked fine. I'm assuming RA motor get the power first since it is always moving.

#45 TopherTheME

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Posted 06 November 2012 - 12:18 PM

I would grab a DMM and start measuring. One thing to keep in mind is that the Dec axis binds very easily on the CG-5. If a motor is stuck and can't rotate it becomes a resistor and will pull a lot of current. Make sure your DEC axis is free by removing/loosening the Dec motor and worm gear.

#46 ptsouth97

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Posted 19 November 2012 - 05:10 PM

Ok, I have checked for continuity. Is there a schematic somewhere that shows what values I should be getting with a DMM? I searched the Internet with no luck.

Also, how do I tell how loose the dec axis should be?






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