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GPS 11" Right/Left no longer responding

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#1 simr49

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Posted 14 October 2021 - 10:14 AM

Greetings all, 

This is my first post on CN and really appreciate all the amazing things I've learned from you all so far here. Last year I purchased a used 2001 model GPS 11" and have loved it! Unfortunately, I think the MC board has failed. When aligning the scope no longer moves left/right and the controller left/right buttons don't respond other than showing the "Rate" number on the display when I press them. I disassembled the scope and swapped the up/down, left/right motor control plugs and up/down buttons do move it right to left so I know the motor is good, but at this point not sure what else to try. I contacted Celestron and they were very helpful, but basically said they can't parts for this old beast anymore and recommended a new mount. I guess my question to you all is is there any other troubleshooting I can do or should I be looking at a new mount? If I'm looking at a new mount, what mount and parts would be needed to make this happen? I saw a few posts similar for an 8" GPS user in a similar situation, but not sure if an Evolution mount could handle the 11" payload. No special accessories mounted at this point, just the scope and finder.

 

Thanks for any help/input you can offer. 

Ryan



#2 markb

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Posted 14 October 2021 - 10:39 AM

I would have tried swapping in another controller before digging too deeply. HCs are generally bullet proof except for dim displays, but can fail. Has your GPS11 been upgraded to the 'normal' cable update flash version levels? EEPROMs have been known to fail and lose or not accept programming. Chips can been burned and swapped in but a newer used HC will work fine. 

 

With minor programming quirks the nexstar HCs are interchangable except for the original 1999 N 5/8 without vixen clamp. A 4.22 is the best one for the GPS11, but mine behaves even with the 5.x Plus.

 

https://ww.nexstarsi...GPSFirmware.htm

 

HC v.4.x and MB v3.x are the minimum version levels to do the 'normal' flash via cable.

 

There is a long thread that now has pretty complete 'old school' external flash programmer instructions (my post-prototype early release needed a programmed chip desolder swap, but yours is newer and the thread instructions will work).

 

As last year the motor board was still available. NWS200 perhaps? NXW200 My memory says Highpoint had some of the OEM stock. Right vendor but don't see any listed, perhaps call them.

 

A WTB ad is likely to chase a full mount out of a closet. Lots were de-tubed.

 

Good luck diagnosing.


Edited by markb, 14 October 2021 - 10:48 AM.


#3 simr49

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Posted 14 October 2021 - 11:06 AM

Really appreciate it. I'll give the HC a try first. I haven't updated firmware yet, but may give that a try as well. I just felt it would be odd for the control board to just stop working. The HC is intermittently going dim so maybe it's on its last leg. I hate to ditch the mount. Been really solid for me and easy to move around. I did find a mount on ebay, but they wanted $1000 for it plus shipping. Just seems high since I only paid $1000 for my whole scope with mount and tripod last year. 



#4 Jack J

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Posted 14 October 2021 - 11:25 AM

Really appreciate it. I'll give the HC a try first. I haven't updated firmware yet, but may give that a try as well. I just felt it would be odd for the control board to just stop working. The HC is intermittently going dim so maybe it's on its last leg. I hate to ditch the mount. Been really solid for me and easy to move around. I did find a mount on ebay, but they wanted $1000 for it plus shipping. Just seems high since I only paid $1000 for my whole scope with mount and tripod last year. 

Remember those buttons on the HC have probably been used a lot in the past 20yrs.  Dirt, dust, etc., can get into them and the switch can just wear out after repeated use.  Look at the RC's for other electronic items and you see they do fail after awhile. My cable box is one too.  Good advice to try another HC that is KNOWN to work and then go from there.  Good luck!!! 



#5 simr49

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Posted 14 October 2021 - 11:32 AM

So could the HC still be failing if I see the display register the current rate setting when hit the left or right directional button on the HC? Just curious if it's normal to see the current rate on a healthy HC. I'm working on getting a working spare so I'll update the thread with findings. Again, really appreciate the support y'all! - Ryan



#6 rkinnett

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Posted 14 October 2021 - 11:33 AM

If you press left/right and see any response on screen, that indicates that buttons are working fine and the HC is probably good as well.

 

A common troubleshooting trick for single-axis-not-moving problems is to swap your motor connectors.

 

Right now your dec control is working, and RA control is not.  This means your dec motor and dec drive circuits are working, and either your RA motor or RA drive circuit is not.

 

Swap your RA motor to the Dec drive connector and vice-versa.

 

If you press up and down and see motion on RA, then you know the RA motor is good and the problem is with the RA drive circuit.

 

If you press left and right and see motion on dec, then you know the RA drive circuit is good and the problem is with the RA motor.

 

If you press up, down, left, and right and see no motion then both your RA motor and RA drive circuit are bad.

 

A common problem with older (10+ years) circuits is electrolytic capacitors.  Look for any signs of bulging or leaking around the bigger caps.  This isn't a definitive check - they could be bad but not show visible signs, but it's a start.



#7 markb

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Posted 14 October 2021 - 11:37 AM

Without in hand, it is hard to isolate the HC to a bad chip or just a dirty keypad.

 

The keypad can be removed and sort of cleaned for testing (circuit trace contacts too), but I've never had any luck getting cruddy rubber keypad contacts to last. There is a chemical refinishing process, the old one was taken off the market presumably for safety reasons due to chemical content, and I believe I saw one recently but did not save the link.

 

If you do a clean up with high percentage alcohol you can see if it makes a difference on the pad action, but I think one of us is probably right, either bad HC or a bad motor board. Again very difficult to diagnose without it in your hands.



#8 simr49

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Posted 14 October 2021 - 11:49 AM

That makes sense. I think that's pretty much where I'm at this point. Up/Down buttons did move RA when I swapped it dec contol on the board, and RA buttons still didn't work for dec so motor is good, board may be bad. I'll check capacitors. Do you guys know if anyone that does repairs on these old components? I'm a pretty technical guy, but don't have experience working on these small circuits and would likely end up having a nervous breakdown. It's sad to me these good mounts get put out to pasture over such simple component failure. 



#9 markb

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Posted 14 October 2021 - 12:29 PM

Try a HC first. Programming bit level errors, on the 'right' spot, or a component failure on the HC (I've seen smd components fall off or just be cold soldered) could do this, and HCs are common as dirt since they still make newer versions, and they don't self destruct like Autostars (had two or three die, best guess is extreme static sensitivity out of the mount).

 

Unlike Meade's these don't have a regular cap failure mode. But age would make caps a candidate. There are several electrolytics, I assume at least some are in motor driver circuits.

 

Whatever you do don't overcook the board traces, always a danger on old boards with heavy component leads. I bought a temperature controlled hot air capable soldering station just for the job of swapping my EEPROMs on my early MB, fresh top grade solder wick and liquid flux, too. I never did well with the spring loaded vacuum tools and did not find a power one. Had my fingers crossed the whole time.

 

As for repair, George here on CN used to do these, not as a business AFAIK. I'll try to find his user I'd, or send a PM to Mike Swanson, the Nexstar guru, for a referral.


Edited by markb, 14 October 2021 - 12:55 PM.


#10 markb

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Posted 14 October 2021 - 12:47 PM

George is Geo. here and was a vendor.

 

His user name no longer links to a profile, so he may be gone from CN (or worse, as he is an older gentleman).

 

His posts may provide some clues, here is a representative one (note he suggested a HC swap too in that post), he did board level repairs

 

https://www.cloudyni...e-16/?p=7901345

 

Also, It reminded me that you are not getting the usually MC error codes (including 16 and 17), so I strongly recommend not messing with the motor board until you've exhausted all other possibilities. All other possibilities. They are impossible to get as a part unless Highpoint or someone else has NOS replacement boards, $250 last I saw, but worth it.

 

Also, given celestron's extremely spotty, to be kind, history on telephone help, I would simultaneously send them an email and call and request a supervisor to find out if someone can see if they actually do have NXW200 boards. 

 

If you have the part number in advance it may make all the difference in checking stock. Same for Highpoint.



#11 simr49

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Posted 14 October 2021 - 01:40 PM

Thanks much guys! So you're saying that typically if there is any kind of MC malfunction the HC would display an error code? Correct, I'm not getting any codes on the HC. Thanks for the link to George's post. It was very informative. The capacitors/board in general look really clean (no swelling or sign of corrosion). I cleaned the HC contacts and reseated all connections on the HC and the mount. Same problem persists unfortunately. I need to check the version on my HC and just get one ordered and we'll see if that solves it. You guys are the best!



#12 simr49

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Posted 14 October 2021 - 02:08 PM

I found this on ebay. The guy can't tell me the version, but could this one work for me? https://www.ebay.com...-EAAOSwoB1hWPaB



#13 markb

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Posted 14 October 2021 - 03:07 PM

The non Plus are safest, some GPS serial boards reportedly do odd things with a Plus HC (motor runs after button released?). My slightly older one is fine with a Plus. I prefer it, actually, and use the RS232 plug one so I can use a StarBT bluetooth to use SkySafari Plus for control. All before Plus were RS232 models.

 

See

https://nexstarsite....mpatibility.htm

for Mike's compatibility notes.

 

Ones without a swoop are the (very rare) ones without a swoop under the display.

 

The one in the ad looks like a non-plus. It likely would need to be updated for the GPS to function (illegitimate brother of the Y2K date issue, the GPS 17 year rollover issue requiem updates for GPS function), but will work fine with manual date and time input if not the latest update, so you'll need to check your current HC MB versions and Mike's site first.

 

USB Plus units (a notch at the HC bottom indicates USB models) let you avoid the cable and serial to usb adapter expense. But they are 5.x only IIRC. Some folks will get the run on issue

 

A pain to learn the older Nexstar quirks, but Mike's site and book info (buy his book) is invaluable.

 

That price on that listing seems a bit high and the stretched cord looks funky, I might keep looking.

 

You can 'Save a Search' on Ebay to get notified of new listings, I have a lot set for my addictions, I mean hobbies.

 

A CN Want ad is likely to work too.

 

Ebay sales history has most HCs sold at $55+ recently.

 

Also, add your general location to your profile box, in case someone is near enough to lend one to you. I think I sold my spares or I would have PMed you already.

 

Even a 2.x non upgradable HC will let you test, at least.

 

I did more looking.

 

I forgot the GPS11 MB is the same as the 5i/8i, again, not easy to find used.

 

IF the HC doesn't do it (easy to resell),  call Celestron with the NXW200 board designation and see what they know.

 

https://www.celestro...ries-telescopes

Out of stock

https://www.highpoin...eplacement-part

 

The GPS11 is a wonderful scope. With 4.x or 5.x firmware I find a careful level helps go tos (north and autolevel died with a lawsuit imposed change, the new align methods are excellent, even with the robot-scope fun gone. . I use a Baader Alan Gee TC with a true 2" diagonal kludge to get f4.9-f5, love it even more now.

 

Best of luck. You can PM if you want, too.



#14 JMP

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Posted 14 October 2021 - 07:42 PM

Woodland Hills (telescopes.net) may have the board in stock.
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#15 simr49

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Posted 15 October 2021 - 08:52 AM

Really appreciate the input guys! Kinda blown away with the support on this forum. You guys are the best! I'll keep my eye for a deal on an HC and the board. Even if it's not the board it may not hurt to have a spare on hand or in case someone else on here needs one down the road. I just moved outside of town and winter is coming, so hopefully I can get this resolved soon. Can't wait to get out on the clear nights coming! I'll be sure to keep you posted on what I find or WHEN I get this resolved. 



#16 mclewis1

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Posted 15 October 2021 - 10:06 AM

If you believe the HC and MC are at least initially functioning correctly (no error codes but perhaps just a failure of the keypad) you can bypass the initial alignment functionality of the physical HC by connecting it to a PC via the HC serial port on it's backside (the little RJ9 connection), using a Celestron HC serial cable (#93920), a RS232 serial to USB adapter, and running NexRemote on a Windows PC. When doing this NexRemote becomes the HC.

 

Another connectivity option to completely bypass the physical HC is to use the long discontinued Celestron PC Port cable (#93922) and adapter (connected via the PC Port on the base of the NS GPS scopes), and an RS232 Serial to USB adapter, Windows PC, and the NexRemote software. 

 

Information on these various connectivity options is available on Mike Swanson's website - www.nexstarsite.com

 

Finding functional v2 or v4 HCs is very very difficult these days. A newer model v5 (NexStar+) HC may work but there can be issues getting one to work reliably with older NS GPS scopes. 

 

Another option is to build the nice simple WiFi/Ethernet Arduino module that mlord defined in a few threads. This will allow you to entirely remove a physical HC and use a variety of up to date apps to align and control the scope.

 

But all of this does assume that your MC board inside the scope is functional. If you believe that the MC board is functional (no error codes, and using an alternative HC functionality works) then I would NOT touch the firmware. The only time I'd consider this step is if you intend to use a NS+ HC or the WiFi module and your scope doesn't currently work with it (which most of the time won't be necessary). Yes, this would require that you first verify the MC is indeed functioning by running a lower level HC (either a replacement v4 HC or NexRemote), otherwise you are just guessing about whether you have a bad MC or just down level firmware that might be causing a problem with the new HC options. 


Edited by mclewis1, 15 October 2021 - 10:13 AM.


#17 markb

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Posted 15 October 2021 - 04:01 PM

My recollection is that Mike Swanson has said the Plus 5.x HC 'issue' (continuing to slew after a button is released) was a serial board based issue (the board screwed to the top panel of the mount base, with all the top base connectors soldered to it), and not the MB. He has a workaround, see below.

 

They had several versions of the serial interface board, some worked with Plus controllers, some had issues. My extremely early GPS11 is fine, as is my 2006 GPS11.

 

As far as MB firmware, Mike's site has the MB version to HC version information, I think at the link I posted before.

 

With the correct cabling, I've never had an issue updating MB firmware, but once you're up to a usable version there's no real reason to do it.

 

If using a USB to serial adapter, as most people are these days, I would suggest using only the Trendnet sold on Amazon. This was the one celestronomed on their web page some time back. One specific chipset works better than others, but some with that chips that do not implement on the commands and fail mid update. The Trendnet has been fine, over something like 10 HC updates (I accumulated a big pile at one point) and 2 or 3 MC updates.

 

The HC from has to be the latest GPS fixed version for the GPS to work, although the old 2.2 handsets can still be used with manual time and location entry.

 

Before they posted the fix I would get my time and location off Sky Safari, which displayed on the screen. It was manual entry only, but worked over a single session.

 

Mike has instructions on loading a specific HC firmware that seems to reduce or eliminate the plus runaway slew issue, as well as tricking the software to use it. I think here on CN and on his site. The needed d/l is also around.

 

https://www.nexstars...xStarGPSFix.htm

 

But then the GPS fix is not applied and GPS won't work.

 

IIRC there are pinout instructions around to make the PC cable, as well as the serial cable floating around. As of last year there were still people selling them on eBay.



#18 simr49

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Posted 18 October 2021 - 11:28 AM

Thanks guys! I'm planning to test with the serial cable/PC soon to see if I can rule out the MC. Keep you posted!



#19 simr49

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Posted Yesterday, 03:21 PM

Well, I found a fully functional GPS 11 mount that will be here on Thursday. It has the same version HC that I have and same firmware HC and MC. I'll try the new HC first and see what happens, but either way I'll be able to get my old mount working with the spare parts. The good thing is I'll have a spare parts mount if needed for this old beast. Of course if others on the forum get in a bind and need parts, let me know. I'll let you all know how things shake out. 



#20 markb

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Posted Yesterday, 08:36 PM

Best of luck, hopefully the hand control will verify as good in your incoming GPS 11, and it will then bring your old one back to life.

 

If you are able to pull the version numbers with the hand controller you currently have, you should do so. On the current mount, and check the new one when it shows.

 

Swapping OTAs is possible but not trivial

 

You can check the information on the links we posted earlier on Mike's site, but my recollection is that the 4.x and 5.x plus hand controls only work on MB versions 3.0 x and 4.x, but I'd have to go back and check for sure.

 

Before I changed my MB chips from v1.0 to 4.x, none of the newer controllers worked, only the original HC 1.6.

 

I'll have to look for the CN post so I don't have to type it all again, but I personally found with my two GPS 11s that they had to be plugged in and left plugged in for two or three days in an area where they could 'see' the satellites in order to download a fresh ephemeris (I believe that is the proper term, or almanac) and actually deliver GPS and time settings that made sense.

 

I had nonsensical responses from the GPS boards that resulted, not from the HC version and roll over issue, but rather, from simply not having downloaded the full current satellite information. All of the previously downloaded information was outdated and caused the problem.

 

Overlaid on this, I also had dead batteries and even a dead oncore gps board, but the two or three day (I'm extending it for safety, I think 1 to 2 worked but it's been a couple of years) time within satellite range in order to download the current title information has not been reported elsewhere to my knowledge.

 

My experiences were from two totally different versions of the GPS system, one in the arm and the other of the original Motorola board in the base. So I know it to be a real issue for GPS11s stored for an extended time.

 

Incidentally, the Oncore boards were used in many fixed installations without batteries, and having a discharged battery will extend connect time but not massively like the download issue. 

 

I did have a bad battery keep my arm mounted later GPS hang and not connect, bit I think it was an internal battery short pulling down the circuit. It worked fine AFAIR without battery, which I did replace.

 

Hopefully you'll end up with two completely working mounts.


Edited by markb, Yesterday, 08:54 PM.


#21 simr49

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Posted Today, 08:42 AM

Thanks! That's very interesting regarding the GPS download information. Was it able to pull that information indoors or did you have to leave it outside to pull the information? I know sometimes mine would actually be able to slew to a star from inside the house when testing alignment. 



#22 whizbang

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Posted Today, 09:04 AM

BTW...

 

What firmware versions do you have?



#23 markb

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Posted Today, 11:13 AM

+1 on posting your firmware version displays.

 

I also did Nexstar rough slew testing on my first Gen 5/8 indoors to find out some basics on a clamp conversion, but that was non GPS.

 

I don't think you ever said, also, whether you were getting accurate GPS data on your current set up. By accurate, I mean within several years and basic lat/long, not the details. If GPS data looks fine, it should be. The rollover gave years out of date IIRC, and other GPS issues don't come even close to your home location, if you don't get the 00 00 00 displays I'm pretty sure I recall receiving before the download ended.

 

EDIT They used several GPS board types, so some details may vary. Mine was the first base mounted Motorola OnCore, not Celestron specific, and the 2006 arm mounted GPS.

 

I had a south facing window that I knew worked for other GPS devices, both handheld GPS only, so I tried that first and it worked, perhaps a bit slowly on link up, but worked. If it hadn't I would have tried my yard.

 

It also let me try out my Talentcell battery from Amazon that I learned about on CN. I have the mid range one, around $40 or so, comes with the Celestron barrel plug size, it's the size and weight, about, of a regular paperback, and runs the big guy for hours.

 

I hang it off the mount in a net bag, easiest solid power I could imagine, minimal cord annoyances. Recommended.

 

And with a usb port it can power a tablet if necessary.

 

Another great add on for Android, and the RS232 serial style HC (no way to power it off the usb type Plus HC, and iOS Apple only does wifi) is the StarBT bluetooth from http://Astro-gadget.net in the Ukraine.

 

Most affordable I've found and zero issues, zero, for me. BT connect it to an inexpensive android tablet like my ancient Tab 4 and use SkySafari 6 with the Plus add on (under $10 when added it). Pro isn't necessary but Plus gives you remote control.

 

They make a wifi as well.

 

The other big help if you take the mount off the tripod is the Starizona Landing Pad. I have one for the GPS11 and one for the CPC that i took a shot on for my portable pier mod.. Both worked on my GPS11. They worked on my N5/8 too, after redrilling the base hole pattern and peeling off the rubber feet.

 

Don't bother with looking for used ones, it looks like they dropped the price to a very reasonable $50 on the black tripod and CPC. The other one is 80.

 

Good luck


Edited by markb, Today, 11:16 AM.



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