Nortel Trimble NTGS50AA-08: Help needed - Page 1
Forum section: electronics / general

author: Zermalmer
author_rank: Regular Contributor
timestamp: April 12, 2018, 10:17:39 pm
content: Hi everyone,I bought a Nortel NTGS50AA at the end of last year... first testing worked ok... I also where able to setup LH on win and a communication.2 weeks ago I decided to setup LH on a raspi and make long time tests to decide what I maybe log and how to manage this logs.I where able to run the device over 6h without any problems and wrote at least a 4h xml logfile (my son decided to try this)All this was "on the fly" and worked quite good enough to try to run a long time test in a lab enviorement to compare it with stuff there.I decided to move the epuipment and after finding a temporary position for the GPS antenna the system in generel worked for ~3h.I keep the system running and wanted to know how it develped over night.Now the problem:Next day I found the raspi stuck with no additional data... thought it was because of missing additional RAM or storage possibility of the raspi, which is running only from SD card.Restarting the raspi doesn't fix it.I take the trimble from power and restarted it.Everything than seemd to work again... but only for less than half an hour... it stucked again.A closer look shows me the red fail LED of the device (didn't noticed it before because of orientation of the device.today I assembled it again at home and it worked for at least an hour... until it "crashed" againok, I had only 4 sats (sometimes 5 or 6) and in last attempt it decided to not that the saved position is bad, but I am sure that can'T be the problemI attached some pics from the last screen which heather displayed.Remarkable is the jump rigth before the end of the plot... looks like the system want to adjust something but where not able to do this and set it into halt and failure mode.Any suggestions what I can check or what went wrong?

author: ArthurDent
author_rank: Super Contributor
timestamp: April 13, 2018, 12:50:14 am
content: Your antenna signal seems to be the problem. If you check the number of satellites displayed on the bottom trace, the number drops exactly when the other graph lines go nuts. The pps numbers and the osc numbers are really bad. Here is a graph from one of my NTGS units. If you use the 3 commands G O ENTER then G O 500 ENTER you will also graph the oscillator at 500 ppt.

author: ArthurDent
author_rank: Super Contributor
timestamp: April 13, 2018, 01:01:04 am
content: Here is another graph on another unit with ADEV numbers displayed instead of the circle graphs. You can see there is a huge difference between the graphs I've displayed and yours when it is running.

author: texaspyro
author_rank: Super Contributor
timestamp: April 13, 2018, 03:34:22 am
content: "Saved position bad" means that you need to do a self-survey (SS command) or enter your known, ACCURATE location (SL command).

author: Zermalmer
author_rank: Regular Contributor
timestamp: April 13, 2018, 12:09:59 pm
content: Thanks ArthurDent and texaspyro for your fast answers.I will soon give it a try and I will have a look if something is wrong inside of the GPS antenna... it's a used one, which was mounted on a boat.

author: ArthurDent
author_rank: Super Contributor
timestamp: April 13, 2018, 02:00:12 pm
content: I am not saying there is something wrong with your GPS antenna, just that you are receiving few satellites and/or on many satellites the signal is too weak to track them. If you look at your graph and see where you get those huge jumps in the display, you will see that it is exactly when you lose one of the few satellites your antenna could see. Where you can receive a good strong signal from at least one satellite then the antenna isn’t a problem and probably not the receiver either but just the antenna location. I think when you get a good signal your receiver will work. I’ve found that if you have a good strong signal from multiple satellites the 10 Mhz output will be more stable as well.Texaspyro knows Lady Heather inside and out for a very good reason and his advice is good for correcting the ‘saved position bad’ message. On all the NTGS units I sell I make sure this isn’t a problem by forcing a survey so the receiver knows where it is and you don’t get that message. Here is part of the information I send with my units:“NOTE:Before this GPSTM was shipped I sent a hard reset to the unit so it will run a full survey when powered up and this could take a couple of hours. Make sure that it is connected to a good active antenna with a clear view of the sky. After it has run the complete survey, use Lady Heather’s ‘e’ command from the keyboard to save the position and allow much faster lock when it is repowered.This is a quick overview of how to get your GPSTM up and running. All you have to do to use the receiver to get 10Mhz is to connect it to your 5V active GPS antenna and plug it in. A 26dB gain antenna with a clear view of the sky is recommended. Note that before this GPSTM was shipped to you that a ‘set to factory defaults’ command was sent to the unit. This means that when you first power the GPSTM on it won’t get confused trying to still find satellites thinking it’s at my saved location. The GPSTM will do a survey to locate its position and this will take some time. You can monitor its progress using Lady Heather. For a detailed explanation of the software you should read the ‘Lady Heather docs 1’ text file on the included disk. That file goes in to great detail on how to modify the program to suit your needs.”If your location on your graph is correct, it looks like you are in a large building complex with sky views only to the southeast. That will probably restrict the number of satellites you can receive and signal reflections off the building may be a problem as well. If you look at the signal strength/satellite location chart of my location for a GPS receiver that has run for a long time you will see that I have pretty good strong coverage. Once you get your receiver running properly, check the chart for your location and see what it looks like.

author: Zermalmer
author_rank: Regular Contributor
timestamp: April 13, 2018, 07:19:29 pm
content: Thx ArthurDent.It looks like my antenna is kille by the previous owner.Today, with clouds on the sky and all day raining, I get absolut nothing.I checked with scope the antenna voltage if the module provide the 5V and it's available.Also checked the cable.I have at first to search for a chance to replace the antenna, which is at the actual time is not really possible...And no shop around which provide antenna which I can use, so I have to order one

author: PA0PBZ
author_rank: Super Contributor
timestamp: April 13, 2018, 07:30:50 pm
content: Does the antenna draw any current? If it's dead just find a way to open it and who knows it's just a burned resistor

author: Zermalmer
author_rank: Regular Contributor
timestamp: April 13, 2018, 08:03:38 pm
content: Hi PA0PBZ,I already opened the antenna.But unfortunatly no obvious damage.For TNC connectors I have no adapters, so I have to improvise something to measure a possible current.(desoldering the cable from the module or making a flywire connection... the signal itself isn't important in the case)If someone is interested... the pics in the attachment are a SANAV GA-88 antennaWill have a look tomorrow/next days what I can do or testADD:looks like I need a current clamp, which I actually didn't have... maybe I have the chance to borrow one next week.

author: Zermalmer
author_rank: Regular Contributor
timestamp: April 20, 2018, 07:11:30 pm
content: I am so disappointed and have no idea where to continue to search for the error.I got an GPS mouse with SMB jack (some here in the forum use this model with the DIY GPSDO's) to be sure that the used GPS antenna isn't the source of the problem. (Antenna have clear view to sky and I also checked with mobile and tablet the availability of satellites (9 to 13 are normally available within some minutes)I set a current meter into the antenna path, to see the current for the active antenna... is a little bit less than 12mA-.I also exchanged the power supply and placed it outside of the case...But I have the same error... system powers up and after several minutes (actually 1 to 5 minutes) the Nortel get stucked and no serial communication is possible.After such a stuck I also have to wait 10 - 20 minutes before successfully powering it up again for a periode mentioned above.Have no additional ideas... is it possible that the DC-DC converter have an error?

author: Zermalmer
author_rank: Regular Contributor
timestamp: April 21, 2018, 06:41:05 pm
content: On the website of ko4bb I find the nortel gps monitorhttp://www.ko4bb.com/getsimple/index.php?id=manuals&dir=02_GPS_Timing/Nortel_GPSand thought it could be an good idea to see the Status of the hardware/status registers right before or after the system halted...Unfortunatly the system simply run into the same state of halt and the serial communication is not longer possible (indicated by the two red lights in the lower left corner) and no usefull infos what was reason for the halt is displayedAt the beginning all looks fine....I made one test with and one without antenna, to see if the program is able to show the missing antenna.Also some querys from the dropdown menus are working fine until the crash.

author: edpalmer42
author_rank: Super Contributor
timestamp: April 21, 2018, 07:18:23 pm
content: Could it be a thermal problem with the board? Does blowing a fan on the board solve the problem or change the time from power up to failure?

author: Zermalmer
author_rank: Regular Contributor
timestamp: April 21, 2018, 07:35:08 pm
content: Looking backward to my initial tests and the latest attempts... could be possible that lower temperature leads to longer time until failure.Latest test was at over 20°C.Before I made the latest test I made an attempt in the cellar (temp <20°C) and from the feeling it tooks a little bit longer until fail.I can make tomorrow an attempt with a blowing fan over the whole device.

author: texaspyro
author_rank: Super Contributor
timestamp: April 22, 2018, 12:36:23 am
content: The GPS RF chain in these devices is driven by the 10 MHz OCXO output... that is why they produce no sawtooth error. It is also why they stop tracking satellites if the OCXO is off freq. I'd say the OCXO heater or EFC is bad. Or possibly the DAC that drives the EFC.Connect it (cold) to Lady Heather, power it up, wait a few seconds, fire up Lady Heather and watch the DAC voltage. I bet it is going to the limit.

author: Zermalmer
author_rank: Regular Contributor
timestamp: April 22, 2018, 12:38:54 pm
content: I attached a screenshot of latest test.Also installed a fan to get more time for collected data, but actually it lasts only some minutes before crashing.I also inspected the whole board again and detected that someone already resoldered the pins of the OCXO.(Actually I am not surprised that the preowner sold this device in the winter)Meanwhile I want to thank all of you for your patience and tips

author: Zermalmer
author_rank: Regular Contributor
timestamp: April 22, 2018, 04:32:03 pm
content: even with the risk of too high humidity I placed the device for some minutes in the freezer... the crash also arrives within some minutes and room temperature isn't reached in a fraction...

author: Zermalmer
author_rank: Regular Contributor
timestamp: April 22, 2018, 10:05:10 pm
content: Is it usefull/make sense to desolder the OCXO and make a 'manual' measurement about voltages, current and frequency output depending on the input?

author: edpalmer42
author_rank: Super Contributor
timestamp: April 22, 2018, 11:28:06 pm
content: I wouldn't bother desoldering the OCXO yet. If you can find the specs for the oscillator that will be very helpful. Monitor the current drain for the entire board. From cold, there should be a significant drop in current after 5 - 15 min. as the OCXO warms up and the heater reduces power. Since this is independent of the processor, you should be able to see it even if the unit locks up.Monitor the EFC voltage. You might see it go to 0V or max volts immediately, but after the warmup period, it should be somewhere in the middle and slowly change after that. Ultimately, it will seem to be stationary. If the unit locks up, anything could happen to this voltage.Monitor the 10 MHz output. Don't worry about the calibration of your counter. You do need to be able to be able to measure to about 1 Hz resolution. Depending on what type of crystal is in the OCXO, the frequency will start above or below 10 MHz and over 30 - 60 minutes home in on its final value. The EFC will affect this, of course, but even if the unit locks up, you should still be able to see the oscillator gradually slide in to its final value. Jumps in EFC will just result in jumps in frequency.If possible, you could also measure the temperature of the OCXO. You should see it slowly warm up and eventually stabilize at a constant temperature.Ideally, this info should be collected by a computer so that you can put them all on the same graph and see how they compare to each other. If there's too much 'noise' due to the board locking up, or the patterns don't match what I've described, then you should consider unsoldering the OCXO. But, since it looks like the previous owner already tried that, (s)he probably found that the OCXO was working fine.Ed

author: Zermalmer
author_rank: Regular Contributor
timestamp: April 23, 2018, 03:47:38 pm
content: Thanks edpalmer, will try to setup the measuring.The "EFC voltage" is the signal to the OCXO which adjusts it, right?(actually not complete familiar with all shortcuts in english)

author: Vgkid
author_rank: Super Contributor
timestamp: April 23, 2018, 04:47:06 pm
content: Quote from: Zermalmer on April 23, 2018, 03:47:38 pmCorrect.

author: Zermalmer
author_rank: Regular Contributor
timestamp: May 01, 2018, 07:12:03 pm
content: Hi,now I had time to make some measurement.The temperatur of the OCXO is ~35°C after some minutesThe whole circuit initially starting at around 350mA and then come down to 170mA after some minutes of running.Also had a look where the EFC and the Ref input of the OCXO running (both measured with multimeter)Vref is 6VVefc is initially 3V but drops to 0 when system hooks up.At this point OCXO output of 10MHz are also down. (before it is very well at 10MHz+/- some Hz naturally)Chip frequency is always at 9,8MHz (at the SMB output)

author: edpalmer42
author_rank: Super Contributor
timestamp: May 01, 2018, 08:05:59 pm
content: Based on those measurements, the OCXO is working just fine. Frequency is good, oven seems to be throttling back properly, and EFC is in the middle of its range at 10 MHz.Unfortunately, that means the problem is in the board itself. I don't know if there's any info available on the circuitry.Ed

author: Zermalmer
author_rank: Regular Contributor
timestamp: May 01, 2018, 09:02:32 pm
content: Sounds good and bad at the same time

author: Zermalmer
author_rank: Regular Contributor
timestamp: May 02, 2018, 09:22:24 pm
content: So...no additional ideas?The only things I have now still in mind is:Is the Lucent DC-DC converter to noisy (worn out) so that the system decide to stuck somewhere?(have to check the voltage outputs with the scope the next days)Is it possible that I accidentally disarranged the settings of the device with a LH command?(the only command which comes to my mind would be the eprom command, but which I thought that I didn't have executed it)Is there a way to 'reset' the device to some kind of default?(have to check handbook if there are some system commands, which I can maybe execute during running system over the nortel GPS monitor)Any further suggestions?

author: texaspyro
author_rank: Super Contributor
timestamp: May 02, 2018, 09:37:35 pm
content: Try !h keyboard command in Lady Heather... hard reset to factory defaults

author: Zermalmer
author_rank: Regular Contributor
timestamp: May 02, 2018, 09:49:53 pm
content: Thanks texaspyro, will try it the next days ...lot of other work around... but I will try it!... every straw I will try to grab.

author: edpalmer42
author_rank: Super Contributor
timestamp: May 02, 2018, 10:06:18 pm
content: Are there any commands for debugging or extra logging that you can enable? If not, can LH be set to be even more domineering and demand data every second or two? Anything to get more data on the system status just before it crashes.Ed

author: Zermalmer
author_rank: Regular Contributor
timestamp: May 02, 2018, 10:25:59 pm
content: If I can implement some commands to the LH win startup or to the config file on a LH on a Pi to activate them and logging them to a file... why not?!If someone have suggestions which commands I can include I would appriciate those info.The faster the commands are established (commandline is for sure the slowest) the better it is.The mystery in my eyes is that the nortel have in general a error system, which is described in the handbook with states of registers.But if I was not able to communicate with the nortel this info is naturally useless if i can't access it.(actually haven't tried simple serial console.. but the blocking of communication with LH and also the GPS monitor tells me, that there will be also no simple serial monitor... but I would try it also over a stand alone VT terminal to be independed of the usb to serial adapter)

author: texaspyro
author_rank: Super Contributor
timestamp: May 02, 2018, 11:43:31 pm
content: No... command line commands are processed before any other commands. Next are any commands from the heather.cfg file.These receivers can either speak a mutant SCPI or Trimble TSIP (which Heather uses). TSIP provides far more info and control than SCPI.

author: Zermalmer
author_rank: Regular Contributor
timestamp: May 07, 2018, 06:44:09 pm
content: Hi,I was able to make a hardreset with !h and afterwards all seemed to be ok (10MHZ still available, locking sats and switching to disciplined)... until some time (30-40 minutes).System halted again.First I thought it was caused bei the SS command within the attempt to get a save position, but an additional reset and another attempt doesn't fixed it back.I also checked the output of the DC-DC converter and output of the voltages are ok (also ripple/noise looks to be ok and within specs of the converter)One thing I noticed:The board stickers states that it runs with Firmware 1.86.The Trimble GPS monitor shows firmware 2.62So I think a preowner updated it.So actually absolutly no idea why the system decides to shutdown the adjusting voltage for the oscialtor.

author: Zermalmer
author_rank: Regular Contributor
timestamp: May 08, 2018, 12:47:05 pm
content: I think I have to write this, because I prematurely wrote something about the seller of the device.I have suspected the he is also read/write here but didn't knew it.I would like to apologize for my thoughtless words.