Author Topic: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver) (Read 470027 times)

TheSteve · « **Reply #75 on:** January 09, 2016, 11:51:04 pm »

TiN bought a Trimble GPSDO with the 73090 OCXO but it should be pretty similar - he took excellent high res pics you can see here:
https://www.eevblog.com/forum/repair/repair-temexspectratime-lpfrslpro-10mhz-rb-generator-%28drifting-like-mad%29/60/

Maybe they can help you find any other faults.

btw, mine also had one capacitor crushed, but it was a bypass cap so I just soldered in a 0.1 uF.

davebb · « **Reply #76 on:** January 11, 2016, 10:51:53 pm »

Hi Steve They are good photos but I am trying to fix my Symmetricom, the seller did ask if I wanted a replacement,and I said yes, we will see how that goes
Thanks Dave,
I have also sold my Icom-7000

Macbeth · « **Reply #77 on:** January 11, 2016, 11:14:08 pm »

Quote from: davebb on January 11, 2016, 10:51:53 pm

Hi Steve They are good photos but I am trying to fix my Symmetricom, the seller did ask if I wanted a replacement,and I said yes, we will see how that goes
Thanks Dave,
I have also sold my Icom-7000

If it's the same seller as mine then don't waste your time. He makes you wait to the ebay limit and asks you to wait a few days extra when it's clear he didn't send a replacement out at all...

Just ask for a refund and be done with it. In fact logically there is no more reasonable option - get the refund, then just buy another one if you trust the seller. Allowing them the option to have an extra month while holding on to your money encourages them to try all their Won Hung Lo tricks of deception taught by no other than Fu Manchu himself

guido · « **Reply #78 on:** January 16, 2016, 05:37:34 pm »

Also got a symmetricom today. Bought from flyxy2015. Arrived fast. It was clearly DOA, the xtal was not on the pcb but was separate in the plastic bag. Don't think it happened during shipping, packaging was fine. Also the housing of the coil next to it was damaged. Later i found a tiny cap on the pcb which had shifted and was only connected on one side.

Futher testing reveiled that the DC to DC converter doesn't work

These things are clearly shipped without any checking

TheSteve · « **Reply #79 on:** January 17, 2016, 12:25:29 am »

Quote from: guido on January 16, 2016, 05:37:34 pm

Also got a symmetricom today. Bought from flyxy2015. Arrived fast. It was clearly DOA, the xtal was not on the pcb but was separate in the plastic bag. Don't think it happened during shipping, packaging was fine. Also the housing of the coil next to it was damaged. Later i found a tiny cap on the pcb which had shifted and was only connected on one side.

Futher testing reveiled that the DC to DC converter doesn't work
These things are clearly shipped without any checking

Take pictures and file for a refund. As was previously stated only ask for a refund, don't let them tell you they will ship you another because they never will.

radar_macgyver · « **Reply #80 on:** January 17, 2016, 12:56:42 am »

Possibly naive question: if so many units are arriving with components ripped off the board, etc., clearly these units have taken a beating. I can imagine they were literally ripped out of some base station equipment for scrap. If this is the case, would the OCXOs have suffered damage too? If so, how would one determine this?

edpalmer42 · « **Reply #81 on:** January 17, 2016, 01:52:28 am »

Quote from: radar_macgyver on January 17, 2016, 12:56:42 am

Possibly naive question: if so many units are arriving with components ripped off the board, etc., clearly these units have taken a beating. I can imagine they were literally ripped out of some base station equipment for scrap. If this is the case, would the OCXOs have suffered damage too? If so, how would one determine this?

All of these surplus OCXOs, GPSDOs, Rubidium Standards, etc. are potentially junk because of the way they've been (mis)handled. That's why they're priced at a fraction of their original value. The only thing you can do is cross your fingers and hit the 'buy' button. I suspect some of the sellers just ship them out and if there's a problem, they ship another. As long as the percentage of bad units is low, everyone wins - eventually.

If an OCXO was damaged by being beat up you could see one or more of the following:
- totally dead
- off frequency
- high harmonics
- high phase noise
- oven dead
- oven stuck on
- assorted intermittents

You get the idea.

Ed

guido · « **Reply #82 on:** January 17, 2016, 08:32:17 pm »

yeah, it's surplus stuff. Formally used in e-bay terms means that it should be working. But most of my gear needed work after buying, this GPS unit is quite modern for me

I got the serial port working and let it run for a while. It locked without problems. Compared my home-brew TXCO/GPS unit with this one on the scope. Looked good, which is more or less a confirmation that the home-brew unit is not that bad.

I need to get a better GPS antenna. Now using small ones behind a window. Not ideal.
And i would like to put a micro on the serial port to show the status on a display.

shempe · « **Reply #83 on:** January 20, 2016, 10:53:23 pm »

My Unit arrived today, not unharmed.

Have not checked it yet.
First I need to clean it, and I am waiting for new IPA.

edit: fixt picture provider

Macbeth · « **Reply #84 on:** January 20, 2016, 11:11:10 pm »

Quote from: shempe on January 20, 2016, 10:53:23 pm

My Unit arrived today, not unharmed.

Looks a lot like my one - the GPS connector has been ripped off the board. I can't view the higher res pics because for some reason FLICKR thinks this is "adult content" and I am not going to sign up for that.

I wish people would just use

which is totally anonymous, no ads, no signups and is free. Or just use eevblogs forum image upload for smaller stuff in the right format.

Macbeth · « **Reply #85 on:** January 20, 2016, 11:42:36 pm »

I think they just hired some brutes to rip the cables out of these things. I mean, there is no excuse for ripping the GPS antenna MCX socket off, the cable isn't even screwed into it.

My own one had a failed 5V to 12V booster module (the TI PTN04050C). You can get them on AliExpress but they aren't cheap. I got an ebay XL6009 booster to do the job instead. But beware - If you do not supply enough amps to begin with @ 5-5.5V then it goes into some weird PSU current sinking destruction mode! In fact I can't run my board with my DP832 no matter what initial amps I set it, while it will run fine on other PSU's providing enough current is used to start it (1.6A @ 5V).

shempe · « **Reply #86 on:** January 21, 2016, 02:38:02 pm »

yes brutes ...
I looked at the pcb today and it looks like only the MCX for the GPS antenna is not there, and a ripped of cap in the lower left corner. Could be worse.
I bought a few pigtail, GPS antenna, and a few dc step up modules just in case, this should arrive in the next days.

Thank´s for the info about current sinking destruction mode I hope my old HP 6267B is up for the task.

davebb · « **Reply #87 on:** January 21, 2016, 09:40:32 pm »

Hi due to the brilliant photos that shempe posted it looks as i now have mine working,it is running a Survey,when i looked at u25 to l17 in the photo i could see there was a track going to the 2 caps to the left of u25 that i had left out as my u25 inverter had been ripped off the board,
thanks Dave

Command Complete
UCCM-P > SYSTem:STATus?
-------------------------------------------------------------------------------
090-03861-03 serial number W561028299 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: 1.33e-08]
ACQUISITION ................................................ [ GPS 1PPS Valid ]
Tracking: 6 ____ Not Tracking: 2 ________ Time ____________________________
PRN El Az C/N PRN El Az GPS 21:27:39 21 JAN 2016
2 27 83 40 24 23 135 GPS Synchronized to UTC
6 17 41 35 31 31 303 ANT DLY +0.000E+00
12 47 71 43 Position ________________________
14 43 245 42 MODE Survey: 13.6% complete
25 82 332 35
29 41 193 37 AVG LAT N 50:51:38.301
AVG LON W 0:56:00.451
AVG HGT +16.08 m (MSL)

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

Command Complete
UCCM-P >

Command Complete
UCCM-P > POSSTATus
-----------------------------------------------------------------------------
1/21/2016 21:37:30
-----------------------------------------------------------------------------
Position : LAT(N 50:51:38.202) LON(W 0:56:0.300) H(23.20 m MSL)
-----------------------------------------------------------------------------
Geometry : PDOP(28.0) HDOP(17.5) VDOP(17.5)
-----------------------------------------------------------------------------
Channel Status
num of visible sats > 8
num of sats tracked > 6
------ Receiver Channel State ------
CH 0 > SateID(2) TrackMode(pos avail) SigValue(39)
CH 1 > SateID(6) TrackMode(pos avail) SigValue(34)
CH 2 > SateID(12) TrackMode(pos avail) SigValue(41)
CH 3 > SateID(14) TrackMode(pos avail) SigValue(41)
CH 4 > SateID(25) TrackMode(pos avail) SigValue(39)
CH 5 > SateID(29) TrackMode(pos avail) SigValue(44)
CH 6 > SateID(0) TrackMode(code search) SigValue(0)
CH 7 > SateID(0) TrackMode(code search) SigValue(0)
CH 8 > SateID(0) TrackMode(code search) SigValue(0)
CH 9 > SateID(0) TrackMode(code search) SigValue(0)
CH 10 > SateID(0) TrackMode(code search) SigValue(0)
CH 11 > SateID(0) TrackMode(code search) SigValue(0)
-----------------------------------------------------------------------------
Rcvr Status(1) :
-----------------------------------------------------------------------------
Antenna Voltage: 5088 mV, Antenna Current: 28 mA
----------------------
UCCM-P > STATus

- UCCM Slot STATE -

1-1. #Now ACTIVE STATUS ---------------- [Master]
1-2. #Before ACTIVE STATUS ------------- [Master Holdover]
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
UCCM-P >

davebb · « **Reply #88 on:** January 22, 2016, 11:44:34 am »

Hi my Symmetricom is doing a survey when ever the power is switched off is there a command to stop this,as my trimble only did this once when i first powerd it up when i received it
Thanks Dave

davebb · « **Reply #89 on:** January 22, 2016, 10:46:08 pm »

Hi if I connect 2.1-3.6v batt to pin 7 vbck ,on the gps module would it stop the unit from doing a Survey every time it is powered off then back on,
Thanks Dave

TheSteve · « **Reply #90 on:** January 22, 2016, 11:25:20 pm »

Its interesting the Trimble and Symmetricom modules don't behave exactly the same being they were clearly designed to be swapped in place of each other. Obviously when in commercial basestation cellular use they would be expected to never lose power.

Macbeth · « **Reply #91 on:** January 22, 2016, 11:53:59 pm »

Indeed. Also the power input being protected with a 10A SMD fuse... WTF? I've found anything over 1.6A is good enough to kickstart it and it then drops immediately to a much lower power consumption. However, the input at the 10A fuse goes through a 8A schottky rectifier and right on to the powering up of the external GPS antenna. I guess they use much more demanding antennas than my "GPS mouse 3.3-5V" in the original application

davebb · « **Reply #92 on:** January 23, 2016, 12:11:15 am »

Hi Steve
yes I was surprised to see that,i would like to know that others are getting the same results as there was a lot of damage to the board,it does seem to be working well now,when I fitted a new u25 inverter ic I used kaynar wire then put hot glue over the top of u25, also I have now found the 1pps signal on both units,like you say the pulse width is short, the u-blox gps 1pps is a lot easier to see, the Symmetricom gps seems a bit more sensitive then the trimble unit
Thanks Dave

davebb · « **Reply #93 on:** January 23, 2016, 12:35:34 am »

Hi Macbeth
Does your Symmetricom do a Survey every time it is powered off then back on
Thanks Dave

Macbeth · « **Reply #94 on:** January 23, 2016, 12:57:34 am »

davebb, Yes it does... Takes a couple of hours...

davebb · « **Reply #95 on:** January 23, 2016, 01:12:40 am »

ok thanks for that, I may try fitting a batt to the pin 7 then that should do it I hope,unless it is just in the Symmetricom firmware to run the Survey after main power out,
Thanks Dave

TheSteve · « **Reply #96 on:** January 23, 2016, 02:29:56 am »

Other then perhaps receive sensitivity it sounds like the better unit to get is the Trimble. No high inrush current, no DC to DC boost supply to fail and it remembers where it is. My Trimble is also plenty sensitive and 12 channel, my Nortel/Trimble unit is 8 channel as is my HP 58540A. I would still like a Symmetricom to compare to but 3 GPSDO's is probably enough.
btw, they all report the same location but only the HP gets the correct elevation, both Trimble designed units are 20 meters off.

davebb · « **Reply #97 on:** January 23, 2016, 02:03:08 pm »

Hi I just fitted a 3v cr2032 batt as a gps batt backup to pin 7 on the gps ,and it did not stop the unit doing a Survey after power out
Dave

Vgkid · « **Reply #98 on:** January 23, 2016, 06:18:28 pm »

Does anyone know the value(something acceptable would work) and size of c108. It is missing, and would be my first smd component i have worked with.

davebb · « **Reply #99 on:** January 23, 2016, 06:59:04 pm »

Hi for c108 I used a 1nf (102) as that's what I had laying around and its working fine,
and you don't have to use a smt cap just use a std cap and solder that to the pads then use some hot glue over it
Dave 2E0DMB


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Author Topic: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver) (Read 470027 times)

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