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Pre 2012 Nexstar GT mount upgrade to use Nexstar+ controller

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#1 MitchK

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Posted 11 February 2020 - 11:53 PM

Hi all, I've been a bit busy performing an upgrade to the pre 2012 Nexstar GT mount I have had for a number of years. As everyone knows, you can not use the Nexstar+ hand control with the unit as it is. However, you can change out the motor control board to a NXW435, do a little wiring modification to the hand control /power plug board wiring, and remove the wires from the MC board plug, and replace them in the correct order, and it will now be able to use the Nexstar+ hand control. I just finished figuring out the wiring changes and installing a board I got from a member here on CN. (Thanks George).

 

 I did this mod to my own mount. If you attempt this mod using this write up, you do so at your own risk. This write up was just to show what I did to modify my mount.

 

My mount was working fine, but I was limited to using the non + HC, and was limited to firmware 4.04, and there haven't been any updates for it in a number of years. The old board/HC combination also would not work with the Celestron GPS module or the SkyPortal WIFI unit. I happen to recently come across a post 2012 GT mount and discovered it would work with both accessories. The older GT and later GT also will not work with the current version of CPWI. My LST mount will, but not the GT's. I can live with that.

 

Another plus with this mod, is you can now use Celestron Firmware Manager  (CFW) to update the Hand Control firmware to the latest (5.31.9200). 

 

I do not know if there will be any future later GT MC board updates (I doubt it), but you can take advantage of future HC firmware updates.

 

So with that all said, here is a quick walk through on how to do the upgrade.

 

First get a NXW435 Motor Control board (MC board).

 

Then remove the two screws holding the plastic cover on the mount.

 

Unplug the hand control wire from the MC board.

 

Separate the two pieces and set the mount portion that holds the MC board to the side. We are going to work with the Hand Control plug/power board.

 

On the outside of the unit, you will see the power plug. Using a 3/8 nut driver (its probably metric, but the 3/8 works) remove the nut that holds the power plug to the plastic case. set nut and lock washer aside.

 

Flip the plastic cover over and remove the three screws that hold the board to the plastic case. remove the board from the case. Set the plastic case aside.

now looking at the wiring soldered to the circuit board. Find the yellow wire, and clip it flush with the board surface. This wire will not be used again. DO NOT cut it at the plug.

 

using a soldering iron, and a short piece of wire, jumper across solder pads 2 and 4. One later GT plug board, that is the only difference between the early and late boards. On th elate board, there is no connection between the two solder pads. ON the late GT board, there is a short trace connecting the two pads.

 

The mod to the plug board is complete.

 

Now on the end of the wiring harness from the plug board, there is a 6pin plug with a wire in all 6 locations. with a marker, mark the location where the white wire is inserted. Carefully remove all the wires with attached plugs from the plug body. I made a tool from a small paperclip that I flattened one end to serve as a pin removal tool. You can also carefully lift the plastic tabs (just a tiny bit, do not break them) and remove the wires. Now starting on the end of the board where the white wire was inserted. move over one slot and insert the wires in the following order.

 

plug board     wire color             pin header

solder pad

 

                                                 1 N/C No wire-- This is the slot you marked with the marker.

1                     White wire          2

2                     Blue wire            4

3                     Red wire             3

5                     Black wire           5

6                     Brown wire          6

 

4                     Yellow wire         Not used

 

You will have the yellow wire left over. You may dispose of it.

 

That's it, the modifications to the plug board are complete. Reinstall the same way you removed it from the plastic housing.

 

Now onto the MC board.

Remove the two motor wire plugs form the MC board. Note the orientation of the existing board. The new MC board will be installed in the same orientation. With the plugs in the same locations.

Remove  the two screws, remove the old board, place the new board, and reinstall the screws. Reattach the motor wires to the board. Making sure you get the Alt motor connected to the Alt socket on the MC board, and the AZ plug to the matching AZ socket. Plug the HC plug board to the socket marked as AUX. check everything over closely to make sure you have everything connected correctly (especially the wires to the AUX socket). Replace the cover. You can install the cover screws now, or wait until you test it. 

 

Plug a Nexstar+ hand control into it socket on the mount, then apply power. The hand control will display Initializing, then it will give directions to start the alignment.

 

At this [point, I press the menu button and scroll through until you get to utility then hit enter. Scroll through the utility menu until you get to version, then press enter. The display will now show the HC firmware (in my case 5.31.9200, and the motor control firmware which should be 5.21. 

 

Pat yourself on the back, you now have a post 2012 Nexstar+ GT.

 

Disclaimer: I did this mod to my own mount. If you attempt this mod using this write up, you do so at your own risk. This write up was just to show what I did to modify my mount.

 

Here are a couple of pictures that show the similarities between the MC boards and the HC plug boards.

 

DSCI1970a.jpg

This picture shows the one difference between the two plug boards

 

DSCI1974a.jpg

This picture is of the original MC board and the NXW435 MC board

 

DSCI1975a.jpg

This picture is of the modified old plug board with pads 2 and 4 jumpered and installed back in the mount.

 

 

 

 

 

 


Edited by MitchK, 12 February 2020 - 10:48 AM.

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#2 Michael_Swanson

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Posted 12 February 2020 - 01:04 AM

Nice!

 

If possible, you should change the topic subject to:

Pre 2012 Nexstar GT mount 

And then in the intro paragraph you can clarify there as well.  Lots of pre-2012 NexStar mounts work fine with the NexStar+ HC (think NexStar SLT, NexStar SE, etc.).

 

Best regards,
Mike Swanson
https://www.NexStarSite.com



#3 MitchK

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Posted 12 February 2020 - 10:51 AM

Michael, good point. I have edited the title and the the intial paragraph to specify GT mount. 

 

Mitch


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#4 dblum

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Posted 27 July 2020 - 12:59 PM

Interesting....

I just picked up a used Nexstar 60GT that has the original firmware (pre 2002).
I was hopeful that I might be able to re purpose its goto mount for a short 114mm reflector my daughter has.
(If not - it still provided an inexpensive chance to play with a goto mount)

It is good to know that there are upgrade paths available for the electronics.

Thank you for sharing!



#5 Don W

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Posted 27 July 2020 - 03:32 PM

There probably isn't an upgrade path for that one. Too old.



#6 Michael_Swanson

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Posted 27 July 2020 - 07:46 PM

Hi Don - actually, that is what this string is all about, upgrading the original GT with the newer MC board :-)


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#7 dblum

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Posted 16 August 2020 - 03:31 AM

Based on another thread, I thought that I would add to this....

It appears that there are variations in the GT motor controller board.
The one that MitchK had in his GT would appear to have the same motor connections as the newer NWX435 board.

Some of the GT mounts (I know that this is true of both my 4GT and my 60GT) have what appears to be an older/larger connector on our motors.

I saw this photo in another member's recent thread:
4GT_vs_NWX435.jpg

And here is a photo from the last time I took my 4GT apart (showing the same board that he had)

4gt Motor Controller.jpg

At a quick glance - in addition to using a smaller pitch on the connectors,
it appears that the connectors have dropped from an 8 pin to a 6 pin - implying changes to the motor encoders as well.


Edited by dblum, 16 August 2020 - 03:34 AM.


#8 MitchK

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Posted 17 August 2020 - 12:06 AM

dblum, 

    You are correct. The GT's with your board are not upgradable via this method. The motors/encoders, and control boards are different. I discussed this issue with a couple of other members a few months ago. We thought you could replace the motors and MCboard, but the main gear is a different size. If memory serves me, it was like 130 tooth on the older mounts and 190 on the later mounts. Don't quote me on the actual tooth count as I am going by memory. The difference in the plug wire count is for the different encoder. The motor only uses 2 of the 6 or 8 wires in these mounts. The encoder use the remaining 4 or 6 wires. So with all of that said, I'm sorry to say, there is not a simple upgrade method for your mounts. 

 

Mitch



#9 Don W

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Posted 17 August 2020 - 02:08 PM

Hi Don - actually, that is what this string is all about, upgrading the original GT with the newer MC board :-)

Wow, I had no idea that was an option. Thanks!



#10 Michael_Swanson

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Posted 18 August 2020 - 01:12 AM

Wow, I had no idea that was an option. Thanks!

But you are correct in that there are some caveats for some of the mounts.  For example, it is certain this will not work with the original NexStar 60GT and 80GT with their much smaller final drive gear.

 

Best regards,
Mike Swanson
https://www.NexStarSite.com



#11 mathxsd

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Posted 02 September 2020 - 05:42 PM

where did you find the NXW435 MC board? how much did you pay?

i have an 130 gt nexstar series and needed to do the replacement of this MC



#12 MitchK

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Posted 02 September 2020 - 06:57 PM

Post an add here on CN in the classifieds section. A member had a bunch of them for sale at one time. Hopefully he still has some.

 

Mitch



#13 krankin123

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Posted 17 September 2021 - 04:01 AM

Hi all, I've been a bit busy performing an upgrade to the pre 2012 Nexstar GT mount I have had for a number of years. As everyone knows, you can not use the Nexstar+ hand control with the unit as it is. However, you can change out the motor control board to a NXW435, do a little wiring modification to the hand control /power plug board wiring, and remove the wires from the MC board plug, and replace them in the correct order, and it will now be able to use the Nexstar+ hand control. I just finished figuring out the wiring changes and installing a board I got from a member here on CN. (Thanks George).

 

 I did this mod to my own mount. If you attempt this mod using this write up, you do so at your own risk. This write up was just to show what I did to modify my mount.

 

My mount was working fine, but I was limited to using the non + HC, and was limited to firmware 4.04, and there haven't been any updates for it in a number of years. The old board/HC combination also would not work with the Celestron GPS module or the SkyPortal WIFI unit. I happen to recently come across a post 2012 GT mount and discovered it would work with both accessories. The older GT and later GT also will not work with the current version of CPWI. My LST mount will, but not the GT's. I can live with that.

 

Another plus with this mod, is you can now use Celestron Firmware Manager  (CFW) to update the Hand Control firmware to the latest (5.31.9200). 

 

I do not know if there will be any future later GT MC board updates (I doubt it), but you can take advantage of future HC firmware updates.

 

So with that all said, here is a quick walk through on how to do the upgrade.

 

First get a NXW435 Motor Control board (MC board).

 

Then remove the two screws holding the plastic cover on the mount.

 

Unplug the hand control wire from the MC board.

 

Separate the two pieces and set the mount portion that holds the MC board to the side. We are going to work with the Hand Control plug/power board.

 

On the outside of the unit, you will see the power plug. Using a 3/8 nut driver (its probably metric, but the 3/8 works) remove the nut that holds the power plug to the plastic case. set nut and lock washer aside.

 

Flip the plastic cover over and remove the three screws that hold the board to the plastic case. remove the board from the case. Set the plastic case aside.

now looking at the wiring soldered to the circuit board. Find the yellow wire, and clip it flush with the board surface. This wire will not be used again. DO NOT cut it at the plug.

 

using a soldering iron, and a short piece of wire, jumper across solder pads 2 and 4. One later GT plug board, that is the only difference between the early and late boards. On th elate board, there is no connection between the two solder pads. ON the late GT board, there is a short trace connecting the two pads.

 

The mod to the plug board is complete.

 

Now on the end of the wiring harness from the plug board, there is a 6pin plug with a wire in all 6 locations. with a marker, mark the location where the white wire is inserted. Carefully remove all the wires with attached plugs from the plug body. I made a tool from a small paperclip that I flattened one end to serve as a pin removal tool. You can also carefully lift the plastic tabs (just a tiny bit, do not break them) and remove the wires. Now starting on the end of the board where the white wire was inserted. move over one slot and insert the wires in the following order.

 

plug board     wire color             pin header

solder pad

 

                                                 1 N/C No wire-- This is the slot you marked with the marker.

1                     White wire          2

2                     Blue wire            4

3                     Red wire             3

5                     Black wire           5

6                     Brown wire          6

 

4                     Yellow wire         Not used

 

You will have the yellow wire left over. You may dispose of it.

 

That's it, the modifications to the plug board are complete. Reinstall the same way you removed it from the plastic housing.

 

Now onto the MC board.

Remove the two motor wire plugs form the MC board. Note the orientation of the existing board. The new MC board will be installed in the same orientation. With the plugs in the same locations.

Remove  the two screws, remove the old board, place the new board, and reinstall the screws. Reattach the motor wires to the board. Making sure you get the Alt motor connected to the Alt socket on the MC board, and the AZ plug to the matching AZ socket. Plug the HC plug board to the socket marked as AUX. check everything over closely to make sure you have everything connected correctly (especially the wires to the AUX socket). Replace the cover. You can install the cover screws now, or wait until you test it. 

 

Plug a Nexstar+ hand control into it socket on the mount, then apply power. The hand control will display Initializing, then it will give directions to start the alignment.

 

At this [point, I press the menu button and scroll through until you get to utility then hit enter. Scroll through the utility menu until you get to version, then press enter. The display will now show the HC firmware (in my case 5.31.9200, and the motor control firmware which should be 5.21. 

 

Pat yourself on the back, you now have a post 2012 Nexstar+ GT.

 

Disclaimer: I did this mod to my own mount. If you attempt this mod using this write up, you do so at your own risk. This write up was just to show what I did to modify my mount.

 

 

Hi, do you have the old driver board for the 114 GT? I blew mine up when I attached the power input connector : (

 



#14 wamphry

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Posted 24 May 2022 - 01:06 PM

Quick question, do you happen to have a photo of the modified plug board connector after you moved the wires in the plug?



#15 wamphry

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Posted 01 June 2022 - 09:22 AM

Nevermind, was able to see it in one of the pictures... I have a 114GT 31142 with the non flashable firmware v104 that came before 4.04. I had taken photos of my board when I received my used mount and telescope, while repairing and cleaning it, from ebay and luckily for me, the board is the one I can upgrade. I had accidentally already purchased a nexstar+ controller not realizing it would't work with my mount. I decided to keep it thinking I might just buy a used slt mount and a rail for the scope. This is a much easier fix. I am sooooo happy to have found this article and thank you for all the hard work in figuring out this mod. Being able to use CPWI and having the ability to design a wedge for my scope saves me a fortune in cash.  I am building the arduino ascom auto focuser for it as well. I also have to do the mirror mod so I can use a DSLR with my newtonian. After all those projects, diy star tracker!  Trying to build a very low cost, decent astrophotography rig for under $1000 and I will post it on cloudy nights if I succeed.  I love projects smile.gif

 

Costs so far:

$120 114GT used on ebay

$140 Nexstar+ hand controller new on amazon

$99 new motor control board for mount - from celestron

$60 Orion focuser - going to try to mod this so it works with ascom

$6 Arduino temp sensor - ebay

$6 Arduino motor shield - ebay

$6 Arduino Micro - ebay

$10 5v Stepper motors - amazon

$45 Eyepiece filter kit - amazon

$8 Rifle rail for a green laser I had lying around to assist in alignment.

 

Right now, costs are $500, currently sourcing a cheap 16-24mp DSLR, looking at spending around $100 for that. So far I am well under budget!


Edited by wamphry, 01 June 2022 - 09:41 AM.


#16 wamphry

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Posted 08 June 2022 - 12:34 PM

So I was able to complete the upgrade of the mother board. Having a few issues I think I can work out. Tried it out and its not working with CPWI and the upgrade program from celestron isn't working. It works fine with NexRemote and Cart du Ciel ascom driver so I think it has something to do with the power/aux board wiring so I ordered the 4/5se power/aux board and i'll map out the wiring to make it work. It does control the mount and it does lunar align and track. I just realized I set the scope in the mount wrong so it wouldn't autoalign but I think it will when I try again tonight hopefully. I also ordered the aux board and I think I will add an aux port to my gt mount for starsense ot wifi or maybe both :)



#17 wamphry

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Posted 22 June 2022 - 11:55 AM

Oh hey!!! I just realized why I couldn't SkyAlign since upgrading to the 4/5 SE MC Board.

 

On the original MC Board, If you stand behind the scope, facing the direction the scope is looking, the mount arm will be on the right side!!!

 

With the new MC Board, standing behind the scope, the mount arm will be on the left!!!

 

I have not verified this yet. I found this out by looking at pictures of the original GT and comparing to 4/5se. I am going to verify this tonight by trying to skyalign both ways, if it fails on the right and aligns on the left, I will edit this post and mark it verified for the next person who trys this upgrade.



#18 Sixptelk

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Posted 23 June 2022 - 07:33 PM

I have the Nexstar 8. It has no provision for a SkySync. I don't know if it's worth it to try to upgrade. About all I need to do is enter the date, time and lat/long. Anyone able to incorporate a GPS into theirs?



#19 TomH1954

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Posted 23 June 2022 - 09:32 PM

I have the Nexstar 8. It has no provision for a SkySync. I don't know if it's worth it to try to upgrade. About all I need to do is enter the date, time and lat/long. Anyone able to incorporate a GPS into theirs?

There is no update for the original Nexstar 8. You're stuck with it's original controller as it can't use newer controllers. It is also not compatible with any accessories.




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