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

[Bryan]

Thanks for taking the time to test. I will try the same this weekend and report back.

p.s. With the receiver off the board are you seeing any activity on the MCU/ main board. Is the MCU transmitting anything or is it silent so to speak.

[PA0PBZ]

I did not take the receiver from a working main board, so I can't test that.

[Bryan]

I did not take the receiver from a working main board, so I can't test that.

Well, hooked up the receiver off board the same as you did, it's dead. No output at all

[Bryan]

Does anyone happen to have a datasheet or specs for the OCXO. All I can find is that it is likely made by C-MAC at one time and rebadged.

[Jacobo]

Having a problem with Trimble 57964. GPS works fine, module can see 7 to 9 satellites. However it never enables output. Initially it looks like this

Code: [Select]

UCCM >stat

               - UCCM Slot STATE-

1-1. #Now ACTIVE STATUS ---------------- [Alarm]
1-2. #Before ACTIVE STATUS ------------- [OCXO Warm]
2-1. #Reference Clock Operation -------- [Not Used]
2-2. #Current Reference Type ----------- [GPS]
2-3. #Current Select Reference --------- [GPS 1PPS]
2-4. #Current Reference Status --------- [Good Accuracy & Stable]
     #GPS STATUS ----------------------- [Available]
     #Priority Level ------------------- [LINK > GPS]
     #ALARM STATUS
     #H/W FAIL [ LINK ]
     #OPERATION ALARM ------------------ [LINK ]
3-1. #PLL STATUS ----------------------- [ENABLE]
3-2. #Current PLL MODE ----------------- [ENABLE][/font]

but after a while switches to external reference

Code: [Select]

UCCM >stat

               - UCCM Slot STATE-

1-1. #Now ACTIVE STATUS ---------------- [Alarm]
1-2. #Before ACTIVE STATUS ------------- [OCXO Warm]
2-1. #Reference Clock Operation -------- [Not Used]
2-2. #Current Reference Type ----------- [NONE]
2-3. #Current Select Reference --------- [X1PPS]
2-4. #Current Reference Status --------- [Good Accuracy & Stable]
     #GPS STATUS ----------------------- [Available]
     #Priority Level ------------------- [LINK > GPS]
     #ALARM STATUS
     #H/W FAIL [ LINK ]
     #OPERATION ALARM ------------------ [LINK ]
3-1. #PLL STATUS ----------------------- [ENABLE]
3-2. #Current PLL MODE ----------------- [ENABLE]

Logs are as follows

Code: [Select]

UCCM >diag:log:read:all?

Log status:   8 entries

L00:16/11/01.23:24:23 Log cleared
L01:99/08/22.00:00:01 Output mode: Alarm
L02:99/08/22.00:00:01 Power up start
L03:99/08/22.00:00:01 A/S change: Slave(HIGH)
L04:99/08/22.00:00:01 REF_SEL change: LINK(HIGH)
L05:16/11/01.23:27:12 Ref available
L06:16/11/01.23:28:27 Ref Change: GPS
L07:16/11/01.23:28:28 Ref chang: External PPS

and SYSTem:STATe? output are

Code: [Select]

UCCM >syst:stat?

-------------------------------------------------------------------------------
57964-05     serial number  86927905     firmware ver  1.0.0.2-01 W-CDMA  mode
-------------------------------------------------------------------------------
Reference Status __________________________   Reference Outputs _______________
XX Ref 8KHz 0: [LOS]
XX Ref 8KHz 1: [LOS]                          TFOM     9            FFOM      1
XX Ref 8KHz 2: [LOS]                          UCCM A Status[ALARM]
XX Ref 8KHz 3: [LOS]
>> GPS: [phase:+1.3E+01, settling]
ACQUISITION ...................................................[GPS 1PPS Valid]
Tracking: 8 ____   Not Tracking: 4 ________   Time ____________________________
PRN  El  Az  C/N   PRN  El  Az                GPS      23:31:27     01 Nov 2016
 22   3  13   41    17  -- ---
  7  53 243   41    15  -- ---                ANT DLY  0 ns
  9  74 193   41    31  -- ---                Position ________________________
 23  59  71   46    19  -- ---                MODE     Hold
  8  21  48   44
 27  24  91   43                              LAT      S  34:YY:XX.607
  3  17   3   43                              LON      E 150:ZZ:WW.968
 30  26 270   36                              HGT               +76.55 m (MSL)




ELEV MASK  5 deg
-------------------------------------------------------------------------------
Regards, hope I'm just missing some command, as I bought this module a while ago and been waiting for GPS antenna to test it, so return period is over on this purchase...

[ZigmundRat]

Have you tried:

SYNC:REF:DISABLE LINK
SYNC:REF:ENABLE GPS
REF:TYPE GPS
OUTP:TP:SEL PP1S

This should force the ref to GPS (and the output to 1PPS).

[Nuno_pt]

On the ACTIVE STATUS the GPS is presenting an ALARM.

Run the hardware alarm? and operation alarm? to see where te error came from.

[Jacobo]

Hi ZigmundRat,

Have you tried:

SYNC:REF:DISABLE LINK
SYNC:REF:ENABLE GPS
REF:TYPE GPS
OUTP:TP:SEL PP1S

This should force the ref to GPS (and the output to 1PPS).

Good point, I was wandering myself. I have tried those commands, all worked except REF:TYPE GPS. which complains - Parameter error

Hi Nuno_pt,

On the ACTIVE STATUS the GPS is presenting an ALARM.

Run the hardware alarm? and operation alarm? to see where te error came from.

No alarms, both operation and hardware alarms return NONE.

[Nuno_pt]

Do you've the GPS antenna connected?

[Jacobo]

Do you've the GPS antenna connected?

Yep. 7 to 9 satellites are visible at any given time.

[Jacobo]

I suspect the OCXO is a culprit. I have connected frequency counter to OCXO output directly and tried to change VFB pin voltage - no frequency shift at all. The issue is that I'm not 100% sure in my frequency counter, this GPSDO was purchased to calibrate it;) Still I think short term stability is enough to check OCXO...

Anyone knows what frequency swing I should expect from Trimble 65256 OCXO?

[Bryan]

Confused, you say no output, but yet say there is output from the OCXO. Do you mean there is no output on the SMA/B connector for 10Mhz but output from the OCXO itself ?

[Jacobo]

Confused, you say no output, but yet say there is output from the OCXO. Do you mean there is no output on the SMA/B connector for 10Mhz but output from the OCXO itself ?

Sorry for confusion. that's correct, no output from SMB connector of GPSDO, I'm checking directly on OCXO pin. After more close look it seems that swing from 0 V to 4 V produces frequency change about +-4Hz. I think it must be an order of magnitude bigger +-40Hz or something.

So I'm still suspect OCXO not able to adjust frequency and PLL can't lock a loop, so it switch to external ref.

[Bryan]

Hmm, so you suspect that the OCXO is defective as it can not be adjusted by the PLL and the MCU is kicking the 10Mhz output off. I suppose that is a possibility. I assume you have done the factory reset. What is the voltage on the OCXO REF pin. I would also carefully look over the board with a magnifying glass and look for any ripped off SMD components. I think it's, more likely there is a missing or defective component that is causing the loss of the 10Mhz output to the connector i.e. the output to the buffer, amplifier etc.. I would even try back tracing a bit on the SMA/B connector and see if that leads anywhere.

[Jacobo]

Hi Bryan,

Thanks for your advise. You are right, I did perform factory reset - it didn't help. actually I have some suspicions, but I didn't want to touch board until I'm negotiating a return... but just now I got response from eBay seller - this scum want's me to return it back, so he can sell it again! and he was brave enough to write it in eBay message! So I might have no other choice but try to fix it myself... and escalate to eBay for a full refund..

Soo.... back to business... vref is 2.7V from memory. Fvb pin swap from 1V to 4V on startup and then stays at 2.7V all the time. Though I can't see much frequency change on OCXO output during startup... +- few Hertz is all I can see. Which is most likely is not enough to lock the loop.

Also after some hours with DMM I found that D13 is short, supposed to be a 2.8V Zener diode according to marks on it. (I have Trimble 57963-B).

[Bryan]

If I recall the control range is 0-5v, so I would suspect that if you are sitting at  2.7v you are fine. If the PLL could not lock would it not be trying to adjust the voltage downward or upwards to the extreme ends of the control range. Hopefully the shorted zener is the issue. Earlier in the thread there is a couple high resolution photos of the board. I would carefully compare looking for a missing SMD component. The boards are really handled rough.

What equipment are you testing the OCXO frequency with?. Strange that the OCXO frequency is only varying slightly upon warm up, unless these are very good OCXO's !!  Would be so great if there was a schematic or flow diagram for these.

Pretty much standard for the response you received from the seller. Which seller was it.

[Jacobo]

Hi Bryan,

that's what I observe - Fvb pin jump from 0.5V to 4.4V during module init, and if I check at that moment it will say that ref is GPS, then module switch to external ref and Vfb back to 2.4V.

And during that 0.5V to 4.4V swing I can see only 10 Hz change on OCXO output pin. obviously that's not enough, so OCXO still my suspect.

As for shorten zenner - I have unsoldered it and pads where zenner supposed to be still short, while zenner itself looks ok. so short must be somewhere else. but I can't find the trace, as it short to the ground... There are too many pins:(

PS: I don't want to name seller as of yet.. But his name been mentioned in t his thread several times;)

[PA0PBZ]

Also after some hours with DMM I found that D13 is short, supposed to be a 2.8V Zener diode according to marks on it. (I have Trimble 57963-B).

Where is this D13? I can't find it on the pcb.
Is your L20 damaged? It is a weak point and used to couple the 10 MHz signal from the OCXO.

[Bryan]

Hi Bryan,

that's what I observe - Fvb pin jump from 0.5V to 4.4V during module init, and if I check at that moment it will say that ref is GPS, then module switch to external ref and Vfb back to 2.4V.

And during that 0.5V to 4.4V swing I can see only 10 Hz change on OCXO output pin. obviously that's not enough, so OCXO still my suspect.

Hmm, that does sound suspect. Perhaps another member could test their working board. Mine is broken so can't test. OCXO can vary quite a lot in the control range and some are fairly narrow so having a 10Hz change may be completely normal. My money is a component missing/broken or defective on the board. If you have a good accurate frequency monitor you could easily yank the OCXO off the board power it up and test it with a variable power supply on the control pin to see what it takes to get to 10MHz. That should eliminate the OCXO and put the blame on the PLL or feedback circuitry.

Another thing to look for is the circuitry around the Mact switch. This switch can put the board in a state where it's outputs a rough 10MHZ if a antenna disconnect is going to occur., what I never got around to testing is does it just set the Vfb pin to 2.5v as a ballpark or so or does it keep the last vfb voltage and hold it their until the unit goes out of holdover. But I think it notifies the user via the RS232 port if activated.

Ok, I think I know which seller. I often wonder why as a seller they advertise as working and then be faced with refunding money for the defective ones. I suppose it's because if you advertised them as for parts only nobody would buy at the going rate. Probably more economical all around to refund the buyers that complain loud enough. Another topic I suppose.

[Jacobo]

PA0PBZ, I can't see any damaged or missing components on the board. D13 is under GPS receiver. After more detailed observation I think that's by design. So at that moment I don't think this is an issue.

Bryan, I can't believe that OCXO have 1ppm regulation, I think crystal aging would be around 5ppm... so regulation must be much wide, so I have ordered a new OCXO and waiting it to arrive.
As for MACT switch - as far as I can say it just enable output, while board still trying to do it's things - like locking OCXO to GPS or whatever reference is. So MACT doesn't impact Vfb at all, to my best understanding.

Another question is how PLL works - I can observe 9.765606kHz signal in PLL UP/DOWN outputs, meaning that this is frequency phase detector is working on. It's 10MHz / 1024, so it's obvious how to get it from OCXO frequency. However, I can't understand how they obtain reference frequency from GPS, as far as I understand there is nothing with such a frequency that comes from GPS sygnal... Anyway it comes from FPGA, so I can't really tell how PLL works, so I assuming it works.

[enaxy]

Hi.
I am from Slovakia. Trimble 57964-15 GPSDO bought from eBay . It works fine.
 Connection via HyperTerminal COM1 is right. But when I run LADY HEATHER or TBOLTMON I do not see anything.

 COM communication I have configured your 9600 8N1 and thus also communicate via Telnet / HyperTerminal.

 Where can I have a problem that Lady Heather and TBOLTMON shows nothing? Thank you.

UCCM Slot STATE-

1-1. #Now ACTIVE STATUS ---------------- [Master]
1-2. #Before ACTIVE STATUS ------------- [OCXO Warm]
2-1. #Reference Clock Operation -------- [Not Used]
2-2. #Current Reference Type ----------- [GPS]
2-3. #Current Select Reference --------- [GPS 1PPS]
2-4. #Current Reference Status --------- [Good Accuracy & Stable]
     #GPS STATUS ----------------------- [Available]
     #Priority Level ------------------- [LINK > GPS]
     #ALARM STATUS
     #H/W FAIL [ LINK ]
     #OPERATION ALARM ------------------ [LINK ]
3-1. #PLL STATUS ----------------------- [ENABLE]
3-2. #Current PLL MODE ----------------- [NORMAL 2 MODE]

[deepskyridge]

TBOLTMON and Lady Heather both use TSIP for comms, the UCCM does not use TSIP.

There was some work on Lady Heather to support the UCCM but I have not seen anything recently.

Gary

[texaspyro]

 Where can I have a problem that Lady Heather and TBOLTMON shows nothing? Thank you.

The version of Lady Heather that works with these "UCCM" receivers should be out in a couple of weeks (really!).  I've been writing some MUCH better documentation for it.  It's up to 3000 lines long now, and I have another 300 or so more to do.

I also just added support for talking to the management interface of the Oscilloquartz Star-4 receivers.

[enaxy]

Thank you so much for your work. I'm excited. It's like a gift for Christmas

[Confucian]

I got my simple 1 in 4 out 10MHz distribution working. The RF transformers are probably overkill but I found them at eBay auction: #251401324712 and could not resist.
Schematic attached and bare PCB at cost if anyone else is interested.

Finally got my distribution amps sorted, Thanks NivagSwerdna for the PCB's and the relevant info. Dont like MCX connectors so went SMA, I used single sided pcb and Lidl's Sardine tins to make screened enclosures.