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

[NivagSwerdna]

Indeed you have C73 missing as I did.  No idea how they managed to lose that one!

In the section between C119 and R89 I also have an unpopulated chip spot so I don't think you have that part missing.

If you look super close it's quite easy to spot the genuinely missing components as the pads are rough

Your board is pretty typical, shame about the antenna connector but again par for the course.. I guess the soldering wasn't good enough to cope with the loving dismantling the board went through in its last hours.

(You should delete the out of focus images; my eyes are squiffy now)

[Macbeth]

Is there a +ve and -ve regulated supply on the board?

The reason I ask is that looking at the 10MHz output... https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/msg913093/#msg913093 it is exactly the right shape so drive both my counter and my function generator. I believe the Siglent spec is 3v3 pp and the Racal counter something similar.

I haven't found any negative rails on the board. You are thinking of op-amps that require +/- supplies maybe?

I would suggest that the 10MHz is simply capacitor coupled - hence the lack of any DC. Trap for young players or maybe I don't quite understand?? 

[NivagSwerdna]

Indeed I'm in the bottom of a young player trap.  I've been doing some research and I think I like the look of LT6551 and perhaps some elements of the TAPR circuit... especially like the 1:1 RF Transformer.  Looks like I can achieve what I want with very few components.  This project is a huge distraction... I never intended to get a GPSDO!

[Nuno_pt]

Indeed you have C73 missing as I did.  No idea how they managed to lose that one!

In the section between C119 and R89 I also have an unpopulated chip spot so I don't think you have that part missing.

If you look super close it's quite easy to spot the genuinely missing components as the pads are rough

Your board is pretty typical, shame about the antenna connector but again par for the course.. I guess the soldering wasn't good enough to cope with the loving dismantling the board went through in its last hours.

(You should delete the out of focus images; my eyes are squiffy now)

Thanks for the help, can you measure the C at the right of that chip, I'm my board is missing that one.

I've deleted the out of focus, sorry for that, I've just upload everything.

So let's see tomorrow what I got here.

 The power (+5V) is plug on the fuse where it says F1?
Where is the GND?

Or is there some better places?

[NivagSwerdna]

I soldered +5V to the end of the fuse F1 and GND to the end of the big Tantalum Cap above that.

Incidentally, the ribbon cable (https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/msg893582/#msg893582) has a group of pins that are 5V and then a group of pins that are GND.

Do not exceed 5v1

[Macbeth]

Do not exceed 5v1

Also power up with at least 1.7A CC. I've found anything much below makes the DC/DC converter go into self destruct mode, whistling away, clamping the DC down to ~3V... It's also not DP832 PSU friendly, try a higher CC on that or find another supply... My guess is an unregulated would make that TI PTN04050C happy as it doesn't fight the constant current mode. 

[Nuno_pt]

Well I've one PSU 15V 35A, so power shouldn't be a problem.

I just have to find the value for C73 and for the C at the left of R89 and right of the chip, on the bottom side of the board.

I suppose C73 should be similar of C94, bypass cap 0.1uF  .
I've here some 100nF 50V and 25V, maybe it will do

But the other I don't have any clue. 

[PA0PBZ]

Had a look at my board and they are both bypass caps, so 0.1u should be fine.

[Nuno_pt]

Had a look at my board and they are both bypass caps, so 0.1u should be fine.

Thanks PA0PBZ, I'll put the two back in, and take another look at the board, then power it up, to see if it lights up anything.
I've measure C62 and C94 and they measure 28.78µF at 120Hz. 

SMA in smd on it's way, to replace all the connectors.

[kutte]

hi to all,
received my Symmetricom board yesterday. As to be exspected some damage could be seen. On the top side xtal y1 is missing, inductor L20 was ripped off. On the botton side capacitor C26 and resistor R83 were missing.
R83 could be easily identified as 103 (10kOhm), C26 is in neighbourhood of C27 which I measured as 1.2 uF. I put in 0.56 uF as a provisory measure.
Inductor L20 I measured as 5uH and replaced with a new one. Since xtal Y1 is missing, I suggested it to be 22.118.400 Hz. Is there any kind soul able to confirm this value?
Unit seems to be working fine when injecting 22118400 Hz from an external generator.
regards Goetz

[Nuno_pt]

My Y1 is mark as B22.11840.

[PA0PBZ]

I've measure C62 and C94 and they measure 28.78µF at 120Hz. 

You are measuring one of the power lines, there's a lot of parallel caps on there

[Nuno_pt]

Ok then 100nF 25V in there, then let's see if it can bring the magic.

Will try with one little GPS antenna that I've here in the bin, don't know if it's active or not.

I've one TTL to mini USB from other project will try to connect it.

Will power it with 6V from an 35A power supply, should be enough.

[PA0PBZ]

I've one TTL to mini USB from other project will try to connect it.

The port is RS232 level, not TTL.

[NivagSwerdna]

Will power it with 6V from an 35A power supply, should be enough.

Indeed, should be enough to fry the onboard DC-DC converter which is rated at 5.5V MAX.

[Nuno_pt]

The port is RS232 level, not TTL.

Doing more than one thing at same time, gives this.

[Nuno_pt]

Will power it with 6V from an 35A power supply, should be enough.

Indeed, should be enough to fry the onboard DC-DC converter which is rated at 5.5V MAX.

So 5 or close enough, should be better. :-)

[NivagSwerdna]

The GPS module RX/TX are at TTL levels.  The board serial I/O, as appears on the pin header, is at RS232 levels.  You can interface with both.

[Nuno_pt]

I've power it today with around 5V after soldering the C73 and also the cap near R89 and the chip, replace both with 100nF 25V caps.
When power DS1 will start red, DS2 will start green, DS1 will go out and DS2 will start blinking green.
DS3 and DS4 will start red, DS3 will turn steady green, DS4 go out, but after a few he came back with both red and green leds light up.
The GPS doesn't have an antenna connected, and even with the antenna connected is the same.

The OCXO is getting warmer as the time pass.

Is this behavior normal on the led's?

Only got one RS232 to TTL module.

Update: I got the attach from one program, but can't find one that let me send commands to the GPS, the file was grap on the GPS pinout, with one TTL to RS-232 USB converter.

What program do you guys use for terminal to send the commands?

[NivagSwerdna]

re: flashing LEDs

Probably; Not sure what they all do, even less sure what they do in fault condition.  In happy state there is a 1Hz Green flasher and a more rapid Green flasher.

You really need to interface with the RS232 level pin-header, that is where you do fun stuff.

Snooping on TX from GPS to GPSDO is good for driving a display or NTP server.  I see you have SV with 0 satellites, not surprising with no antenna!
You can also snoop on RX which shows commands from GPSDO but you can't inject there since it is driven by the GPSDO.

Get a RS232 interface going.

I use Putty because it's on my PC for other things but there are others... RealTerm?

You're not going to get far without an antenna!

[Nuno_pt]

NivagSwerdna thanks.

Well the antenna was an old one from the junk box, I've open it and found it with water and all rusty inside, so no antenna at all. (Maybe this is the cause of the state of DS4?)
Will have to order a new one, don't know yet if one small or one bigger one.

Tomorrow will add one DB9 and connect directly to the DB9 on the PC.

I've Putty also and RealTerm, will have to look better to see where to send the commands.

Regarding the Led's, I'm not sure also about what they do, but all the voltages on the testing points are present and spot on. (I can put here my measurements of the testing points tomorrow).

The OCXO will warm up.

[NivagSwerdna]

re: Antenna eBay auction: #201464346512 is what I have

[Macbeth]

eBay auction: #201464346512 is what I have

That looks exactly the same as mine!

@Nuno_pt

You really want to use the terminal at the RS232 port which is pretty obvious really. Quite strange to go straight in and tap the GPS receiver? All the LEDs will match up with the STATUS, SYST:STAT and other diagnostics. You also have an error log to examine. Looking at LED's will leave you in the dark 

[NivagSwerdna]

>>> All the LEDs will match up with the STATUS, SYST:STAT and other diagnostics.
It's not really that obvious though is it?

The wiring shows... https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/msg909870/#msg909870

4 LEDs, two of which are dual LED... i.e. 6 LEDs in total.

The green sides of both dual LED are driven by the FPGA, otherwise all the others are driven by the microcontroller.  The command LED:GPSLock? seems to suggest that one might correlate to GPS Lock.... maybe the 1Hz flasher?

The mapping isn't obvious.

Code: [Select]

UCCM-P > STATus

                 - 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 ----------- [LINK]
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 ]
3-1. PLL STATUS ------------------------ [Enable]
3-2. Current: PLL MODE ----------------- [NORMAL 2 MODE]
Command Complete

Code: [Select]

UCCM-P > SYSTem:STATus?
-------------------------------------------------------------------------------
090-03861-03   serial number W560935175   firmware ver 1.0.0.2-01     LINK mode
-------------------------------------------------------------------------------
Reference Status __________________________   Reference Outputs _______________
   Ref 8KHz 0: [LOS]
                                              TFOM     2             FFOM     0
                                              UCCM-P Status[ACTIVE]

>> GPS: [phase:  1.00e-08]
ACQUISITION ................................................ [ GPS 1PPS Valid ]
Tracking: 6 ____   Not Tracking: 4 ________   Time ____________________________
PRN  El  Az  C/N   PRN  El  Az                GPS      10:37:32     29 APR 2016
 10  15 323   42    12  10 205                GPS      Synchronized to UTC
 13  53 130   32    15  77 234                ANT DLY  +5.000E-08
 17  23  98   34    20  27 219                Position ________________________
 18  32 292   34    24  48 267                MODE     Hold
 19  11 128   34
 28  37  52   43                              LAT      N  51:25:23.592
                                              LON      W   0:17:26.904
                                              HGT                +9.30 m  (MSL)




ELEV MASK  5 deg
-------------------------------------------------------------------------------

Command Complete
UCCM-P >


[Nuno_pt]

Morning,

I'll have to move my PC, from the other room to my bench if I want to have native RS-232, on the bench I only have a laptop with USB.
I've here one of this converters eBay auction: #http://www.ebay.com/itm/FT232RL-FTDI-Serials-Adapter-Module-Mini-Port-f-Arduino-USB-to-TTL-3-3V-5-5V-GM-/262136733739?hash=item3d0891202b, from what I could find in the web, on the pins we can plug the TTL levels like I was doing yesterday for the Furuno.

But on the sides there are holes for other connections, on the web they say that an cable to RS-232 can be connected on the side holes.

Board ----> RS-232
TXD  ----> Pin 3
RXD ----> Pin 2
GND ----> Pin 5

Will this work?
Since they pass to the FTDI chip and exit the Mini-USB.