A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)

[wkb]

Or induction of a nearby lightning strike killed the RF part of the rx?

[Bad_Driver]

Thanks for all your advices. The cap or resistor isn‘t soldered correctly, one side is loose.
Not a wrong soldering as some of you thought.
Antenna feeding with 5 volts works and the pigtail is ok.
Since I‘m in ongoing discussions with the chinese vendor I wait with further efforts.
I keep you informed.

[DM4DS]

Board Nr. 3 arrived.

What should I say?
Houston,.....

This time the SATs are tracking, the Survey is running, but no PLL lock 

Can´t find any problems on the board.
Wrote the Pyboard seller a message and pictures.

No luck with these things.

[Bad_Driver]

Pyboard Store offered another board with missing parts but with the GPS receiver in good condition
as replacement. I think this is a good compromise. No one can expect for 18€ full inspected and working
boards, there is always the risk of damage from the rough decommissioning process.
So I have to wait again. But more time for family before Xmas!

[DM4DS]

Nice to hear bad Driver that you found a solution.

mine isn´t working. I took parts from the one with the 0.5hz internal error to replace some parts, named U24-U26+ 2Cs in that area. Think to rememeber that I read here that U25 was a problem on one board with no locking PLL.

WKB send me a tested board but it has the same error! No locking PLL. The OCXO is "moved" in wide range from 9.999.993hz up to 10.000.007hz up and down , up and down. The Voltage measured goes from one to other extrem, OCXO follows, no surprise.

This board is locking GPS super fast, has really good RX with my bad antenna and doesn´t lock the PLL. 

Any ideas which part(s) to switch?
Thanks for Help

[Bad_Driver]

Mmh have no great idea. 

First I would replace the ocxo with an function generator and measure the
PLL voltage again some frequencies around 10.000.000 Hz to discover any pattern.
But will it help? No one knows....

[cdev]

2 ideas.

1.) Furuno manual on manualslib

2.) Email Furuno company

[wkb]

Can anyone in the possession of a Trimble UCCM please be so kind to measure if their OCXO produces a voltage on the middle pin
of the OCXO? Middle pin as in "the OCXO has a row of 3 pins and a row of 2 pins. I mean the middle pin in the row of 3".

I am no longer convinced that the OCXO used on this module produces a Vref. Maybe this module has an Vref somewhere on the board itself?

thanks in advance!

Wilko

[wkb]

Which obviously sucks rocks.. This board I sent over to DM4DS in Germany is the one PA0PBZ tested for me. And it worked for him using an original Symmetricom OCXO (an OCXO model which I did not possess).

This posting: https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/msg3287756/#msg3287756

Wilko
(who today is trying to understand his "forever Settling"  Trimble UCCM)

[wkb]

Can anyone in the possession of a Trimble UCCM please be so kind to measure if their OCXO produces a voltage on the middle pin
of the OCXO? Middle pin as in "the OCXO has a row of 3 pins and a row of 2 pins. I mean the middle pin in the row of 3".

I am no longer convinced that the OCXO used on this module produces a Vref. Maybe this module has an Vref somewhere on the board itself?

thanks in advance!

Wilko

Aha... there is a MAX1242 (U25) which is a 12bit DAC ADC on the back of the PCB. Its pin 4 is the reference voltage for the DAC. An unpopulated pair of pads, when populated, connects the OCXO Vref pins to that DAC  ADC



More research is called for..

[wkb]

More research is called for..

Actually there are 2 MAX1242. Both use the same reference apparently.  I would be very interested in the voltage level on pin 4, the DAC's ADC's reference input.

And: what does your R129 measure? It appears to have 300 as marking, but that is not at all what I measure?

Wilko

[cdev]

Maybe you can learn something useful from the long thread here on the TruePosition GPS boards?

 They also use a quite similar looking Furuno GPS.

They use different OCXOs though. Mine has a Bliley sine wave OCXO.

Sometimes they come up for sale for quite reasonable prices. (assuming they are working)

[DM4DS]

Yours must be a different board. On my 3 Boards U25 is a 5pin device. Also the area around looks totally different.

I´m using an OCXO (Bliley) which is working on one board.
Also tested 2 others , working on the "working" one. Another Bliley and 1 Trimble 12V.
With all 3 the same problem on the faulty boards: No Lock and the OCXO is moved ~7hz over/under 10Mhz if I measure the Output.

While I don´t have 2 antennas with enough skyview, i can´t test both side by side 
Must say that I don´t have reception inside building with any kind of antenna. We have steamed windows , type of these modern low energy house windows, which block almost everything. And for open window tests it´s too cold 

Tryed to communicate with Pyboard seller but no reaction yet. If he does not react until monday evening, I open a dispute  2 boards from him and none works.

Still any ideas welcome.

Wish a nice 3rd advent
DM4DS

Can anyone in the possession of a Trimble UCCM please be so kind to measure if their OCXO produces a voltage on the middle pin
of the OCXO? Middle pin as in "the OCXO has a row of 3 pins and a row of 2 pins. I mean the middle pin in the row of 3".

I am no longer convinced that the OCXO used on this module produces a Vref. Maybe this module has an Vref somewhere on the board itself?

thanks in advance!

Wilko

Aha... there is a MAX1242 (U25) which is a 12bit DAC ADC on the back of the PCB. Its pin 4 is the reference voltage for the DAC. An unpopulated pair of pads, when populated, connects the OCXO Vref pins to that DAC  ADC



More research is called for..

[Bad_Driver]

The hint with "True Position" sounds interesting but the only product I found
is an old pencil (seems to be a give away)

https://ebay.us/BN0VOQ
 
It would be interesting to understand if the boards use the Vref of the OCXOs or not.
I have several OCXOs on the shelf, some without internal Vref, some with Vref but
from my 3 TRIMBLE 34310-T 2 have a Vref lower than the needed Vcontrol for 10.000.000 Hz.

Has anyone measured the possible swing of the DAC? Is it limited to 12 V or to Vref of OCXO/other reference?

I used one of this TRIMBLEs (#4) for my HP 53131A as high stability time base and HP uses a 12 bit DAC as well but with
an internal reference not the OCXOs.

As example:
TRIMBLE #1:
Vref=5.9578 V 
Vc (10.000.000 Hz) = 5.9415 V
Delta V for 1 Hz Delta= 0.7517 V

TRIMBLE #2:
Vref=6.070 V 
Vc (10.000.000 Hz) = 8.1525 V
Delta V for 1 Hz Delta= 0.829 V

TRIMBLE #3:
Vref=5.977 V 
Vc (10.000.000 Hz) = 7.491 V
Delta V for 1 Hz Delta= 0.809 V

If the UCCM dosn't use the OCXOs reference I can use all 3 with the board (if I get one working)

[lamaral]

Today I got my Samsung UCCM delivered. All happy, hooked it up, got some console output but turns out it never gets to the UCCM prompt. It gets stuck in the last line of the snippet below.

Any ideas of what is going on here?

Code: [Select]

-> UCCM Manual Boot Start .....
 type any key to boot prompt mode ..........
 Start Auto Boot(1) .....
 Run to Internal Flash Image(Bank 1)......
 FusingTaskProcess start......
 start FPGA fusing from bank_1############
 Done Check .  OK

 Jump to Application......
�
 Probe test : PASS
 FPGA is already fused (0)
 Basic BackUp crc (0xF61C : 0xF61C)
 Basic Backup is read from BACKUP_BASIC_0 ....
 Log Backup is read from LOG_0 ....
 UCCM Application start...... 0x00, 0x00
 All Task Created......
 PllIsrTask start......
 DebugTaskProcess start......
 PllTaskProcess start......
 EngineTaskProcess start......
 TodEvenTaskProcess start......
 TodTaskProcess start......
 CtrlTaskProcess start......
 DataBackUpProcess start......
 vErrorChecks start......

[texaspyro]

What voltage are you running it at?   Mine are all are 6 - 6.5V, not 5V

[wkb]

5.5V should do. Mine is quite happy with that.

Wilko

[lamaral]

I have tried 5.0, 5.5 and 6.0V. Same outcome for all of them.

I'll try 6.5V also.

[texaspyro]

The Samsung units are rather picky.   They throw an alarm (but work) i f the voltage is off.  I use 6V dropped through a Schotky diode (for 5.6 V)

[wkb]

The Samsungs are indeed picky, I also have that experience here.

Using a PSU with a high enough power rating to accomodate the inrush current of the OCXO heater is also important. If the voltage drops during startup the GPSDO sometimes does not correctly start

Wilko

[wkb]

Wrt no UCCM prompt: did you try just hitting ENTER ?  I've seen them only produce a prompt after I did that.. no prompt was displayed on powerup.

[lamaral]

Thanks for the input so far
I did some more testing and no joy.

I'm powering the GPSDO up with a bench power supply, max current is 5A so there is plenty of capacity to deal with the inrush current, I would say.

I have tried pressing enter to get the UCCM prompt, but that didn't do it. Later I'll plug it into my linux PC and try different combinations of CR and LF, since I read somewhere that the Samsung ones mix it up quite a lot.

It's also worth to mention that I'm getting the ACT LED in a solid green and the Alarm LED in a solid red. If I press the MACT push button, the ACT LED starts blinking red and green rapidly, so I guess it's booting up OK, just not getting the terminal?

Also, do you get the same bootup messages on your Samsungs before they give you a prompt? And does that happen all in the same UART/Serial port?

[wkb]

I have tried pressing enter to get the UCCM prompt, but that didn't do it. Later I'll plug it into my linux PC and try different combinations of CR and LF, since I read somewhere that the Samsung ones mix it up quite a lot.

It's also worth to mention that I'm getting the ACT LED in a solid green and the Alarm LED in a solid red. If I press the MACT push button, the ACT LED starts blinking red and green rapidly, so I guess it's booting up OK, just not getting the terminal?

Also, do you get the same bootup messages on your Samsungs before they give you a prompt? And does that happen all in the same UART/Serial port?

Used Putty on a Windoze PC for connecting to the Samsung UCCM. It is all on the same serial port, the one on pins 32,33,34 on the FPT connector. Note that this is using real RS232 signalling (+ and - 12V)

-> UCCM Manual Boot Start .....
 type any key to boot prompt mode ..........
 Start Auto Boot(1) .....
 Run to Internal Flash Image(Bank 0)......
 FusingTaskProcess start......
 start FPGA fusing from bank_0############
 Done Check .  OK

 Jump to Application......

 Probe test : PASS
 FPGA is already fused (0)
 Basic BackUp crc (0x3689 : 0x3689)
 Basic Backup is read from BACKUP_BASIC_0 ....
 Log Backup is read from LOG_0 ....
 UCCM Application start...... 0x00, 0x00
 All Task Created......
 PllIsrTask start......
 DebugTaskProcess start......
 PllTaskProcess start......
 EngineTaskProcess start......
 TodEvenTaskProcess start......
 TodTaskProcess start......
 CtrlTaskProcess start......
 DataBackUpProcess start......
 vErrorChecks start......
        << had to push Enter here before the UCCM prompt appeared
 UCCM>

[lamaral]

Valuable lesson learned: Never forget your ground.

Turns out I forgot to wire the ground into the serial port. As soon as I got the ground right, it was a matter of pressing enter and magically the UCCM console popped up.

Thanks a lot for the help

[wkb]

Great that it works now!

Willo