I bought the very Last Symmetricom SA.22C in the shop!

[Johnny B Good]

 Did you also verify the 5v rail (pin 6)?

[Name00]

Yes, the 5V rail is good, all voltages look fine measure at point of connections (the pins), I've also verified the GPS pulse and tracked it's output.   I'm able to talk to the interfaces using Lady Heather which I presume also means the unit is fully functional.  Lady heather reports the same thing I'm seeing no Rubidium Lock, the Lock pin also stays high, the manual indicates a +/- 21ppm cyclying for lock without verifying the exact ppm sweep, I see it cycle back and forth on a scope.

I'm waiting for confirmation from the seller it's okay to take it all apart.

[Johnny B Good]

 If the warranty sticker is still intact, I'd be more inclined to request a return with a full refund on the basis of it being "Not fit for purpose" by reason of it being DoA.

 I'm assuming from the fact you've asked the seller for permission to open it up that it had been described as a fully functioning item in the seller's description. The seller will most likely demand some video evidence demonstrating the issue.

 BTW, if you're going to video the scope display and voltage readings, place the camera on a tripod or other suitable support. This will maximise the benefit of processing the video into a more compact format using a video conversion/ compression app (I use Handbrake for this).

 Although the SA.22C is a modernised and more compact version of the venerable LPRO - 101 (same single board smd construction - no pesky electrolytics to spoil your day), unlike the LPRO, no one AFAIAA, has produced / published a comprehensive fault finding guide that could help you repair the more common and fixable faults. Unless you're prepared to do some reverse engineering, the best you can hope for is visually spotting a dry joint or a damaged component (a cracked mlcc, maybe?).

 If the seller gives you permission to open it up, then by all means do so. You never know, contrary to (my) expectations, you just might spot a suspicious looking component / bad solder joint or a broken wire which might allow you to effect a repair. Also, of course, you may be able to detect the glow of the rubidium vapour lamp which will tell you that the lamp itself is still intact.

 If no glow is visible that can also indicate a failure of the excitation oscillator circuit which energises the lamp. If you haven't already done so, it'll be worth downloading the latest LPRO repair guide simply to get some useful hints on how to do some basic tests (temperatures, frequency emissions from the lamp exciter oscillator, voltages and so on).

 Anyway, that's the best I can offer for now.  However, it might be worth posting the results of the health data (w command) for comparison against my own health data (reply #1).

[Name00]

I've opened the unit it all looks clean.  Nothing obvious.  I think the dMP17 value is low looking at yours it seems to translate to around 13.x volts, mine is measuring around 11.x.   According to the life, it's been up for 92.6K hours, ~10.5 years

Mine:
  dMP17: 41306B00.

Yours:
  dMP17: 4159F035.

Going to try to trace the power circuit, maybe a bad cap or resistor somewhere.   I see a slight glow from the lamp.  "w" output below, removed the serial number.


AData:
  SCont: 6012
  SerNum: XXXX
  PwrHrs: 169DC
  PwrTicks: 117E242
  LHHrs: 169DB
  LHTicks: 15576AE
  RHHrs: 169DB
  RHTicks: 14CCDDD
  dMP17: 41306B00.
  dMP5: 3D526F32.
  dHtrVolt: 413FD842.
  PLmp: 3F749718.
  PRes: 3F9D564D.
  dLVthermC: 3C00C400.
  dRVthermC: B8B8C000.
  dLVolt: 3B729566.
  dMVoutC: C931DBB3.
  dTempLo: 41440000.
  dTempHi: 42AF0000.
  dVoltLo: 41389C7C.
  dVoltHi: 4177ACFA.
  iFpgaCtl: 2023
  dCurTemp: 42600000.
  dLVoutC: 3E070F74.
  dRVoutC: 3DECB6DA.
  dMV2demAvg: BA298800.

[EDIT 1] I removed the reply and updated this post instead.  I upped the voltage from a bench power supply to  16v and got a lock.  I was going to initially replace the LM2941CS, however, after tracing the power circuit some more under a microscope and trying to figure out the various parts, I noticed small pits on the solider around Z501, R108, R57, and R28, figuring maybe it was a dry solder.  Ended up apply using a heat gun, and soldering iron, cleaned up most of the solder that may have been marginal.  It's now running solid on 15v with the dMP17 under lady heather at 13.5v

[EDIT 2]  I've run this on a survey fixed location of a LEA-5T (one of those Huawei modules), seems to produce a be far more stable 1 PPS signal when compared to a TAU1201 GNSS module.    Although the unit doesn't seem to be producing any PPS out signal.   Am I missing something?

[cncjerry]

I did a quick scan, and I didn't see anybody mention x72. I have two of these. The second one I just bought, it was in a trutime module. Both mine have quite a few hours on them but they work great. I've never seen version 6 of the software. I also can't remember if the Acmos output is based on the RB disciplined circuitry?  They reference it to a the 60Mhz crystal though some have other crystals, 30Mhz is also known to be available. 

I like these units but they need a heatsink and that takes away from the size.  LH will set the tuning word in both of the versions I have (4.24 and 4.34).  You need version 6 of texaspyro's LH.  Then it is under the '&' command.  You feed it 1pps from somewhere, possibly a well surveyed GPSDO, and it calculates the tuning word and sets it.  Though I have then written it many times after setting it, if it reboots, it is back to factory.  Also, you can set the service pin phase to 0 or 1, that will keep you from thinking it is broken.  The more recent one I have has limits on the control word for output.

Mark (Texaspyro) and I worked together on some of the heatsink mechanics.  I drilled the heatsinks.  He sent me an adapter board, you can get others on eBay now, or design your own and JLCpcb will run them off and have 5 of them to you in a week.  The dimensions are in the manual.  Note that you need specific loading on the sine output as spec'ed in the manual.  Like 150pf and 50r within 4inches of the output.

I run one all the time and tune it twice a year against my symmetricom GPSDO.  Phase noise is poor but stability is good.  The 2nd I plan to discipline with a GPSDO.   

[ohmjke]

Hi everyone.

Worthy of note is the firmware version which predates the later version 6.05C which offers customer access to the 1PPS configuration, along with being able to enable sine wave output.

Johnny B Good, were you able to use 1PPS Synchronization with unit version 6.02c?
Maybe there is some command to enable it in versions earlier than 6.05C?
Or some way to update firmware?

[Johnny B Good]

 roma176 had kindly provided instructions on how to configure it using LH v6 in reply #17 last July by which time I'd just shelved the project in order to concentrate on the LPRO 101 based RFS project. So the answer is "Not just yet.".

 Thanks for attaching the LH screenshot BTW. That should give some clue as to what to expect when I upgrade LH from v 5.0 (I just checked the version installed in my winXP VM).

 I think I'm just about done with the LPRO project, essentially an issue of achieving a stable base plate temperature within +/- 5mK over an ambient temperature range of 14 to 27 deg C.

 I'd recently started experimenting with PID libraries as a possible alternative to my custom in-line coding efforts but finding the documentation as clear as mud on exactly how you're meant to pass a complex set of tuning parameters or even how to link my set point, base plate temperature and fan control variables to the PID.

 As a result I've resorted back to my custom code, based on feed forward with a sort of PID fine tuning of the feed forward control. I made a further refinement which seems to have extended the upper limits of the control range. Even though the fan is powerful enough to hold the base plate to its 36.05 deg set point at an ambient of 32 deg, getting it to perform with a reasonable level of accuracy and stability beyond a maximum of 29 deg has proven impossible to achieve thus far so I might just have to simply live with this shortcoming and take consolation in the fact that I'd managed to get it to cope with close to freezing temperatures (4 deg C) during previous low temperature test runs.

 As for getting a PID library function to work any better than my own controlling algorithm, I suspect it may not even come close (but I'm willing to be proved wrong).

 I'm planning to do another low temperature test Friday night / Saturday morning to make sure my high temperature improvement hasn't compromised its low temperature performance. If it passes the low temperature test, I'll leave it in my garage/workshop to keep the hobby room work bench uncluttered enough to allow me to further experiment with the SA.22C and LH. I might have some news to report in a few days time (or not).

 Whatever the result, I'll be putting that aside in order to complete my MK III ZED 9 T based GPSDO project which I'd also set aside some 5 or 6 months ago. Basically, my problem is that I've got two too many projects than I can cope with right now.

[ohmjke]

Oh, I missed "and so on".
Thought these are the only options:

pressing s and 40 you can set SINE 40%
pressing a and 0 you can disable ACMOS

Will check next time I return to this project.
Thanks.

One more question - does anyone have information where this oscillators (Sa.22c or LPRO-101, for example) actually used?
According to info from seller I bought mine unit it was extracted from some GSM(?) base station. But no more detailed info.
I thinking maybe it is possible to find entire base station on sale and it will be cheaper...
Mine Sa.22c cost was ~$450

[testpoint1]

Oh, I missed "and so on".
Thought these are the only options:

pressing s and 40 you can set SINE 40%
pressing a and 0 you can disable ACMOS

Will check next time I return to this project.
Thanks.

One more question - does anyone have information where this oscillators (Sa.22c or LPRO-101, for example) actually used?
According to info from seller I bought mine unit it was extracted from some GSM(?) base station. But no more detailed info.
I thinking maybe it is possible to find entire base station on sale and it will be cheaper...
Mine Sa.22c cost was ~$450

most of the Rb module just comes from CDMA base station, but SA.22C and X72 are not, since the strange interface of SA.22C, the price of SA.22C is cheap, I am design a mechanical adapter for it, in orfer to use the SA.22C for replace X72 and LPRO, and I will design 2 PCB for the SA.22C.

[lugaw]

Is it possible to change the factory reference crystal on the unit? 

I am planning to buy a unit that doesn't output 10Mhz it only ouput 9.8304MHz from factory.

[Name00]

One more question - does anyone have information where this oscillators (Sa.22c or LPRO-101, for example) actually used?
According to info from seller I bought mine unit it was extracted from some GSM(?) base station. But no more detailed info.
I thinking maybe it is possible to find entire base station on sale and it will be cheaper...
Mine Sa.22c cost was ~$450

If you get ones with 60K+ hours on them, they come from GPRS-EDGE base stations.

Is it possible to change the factory reference crystal on the unit? 

I am planning to buy a unit that doesn't output 10Mhz it only ouput 9.8304MHz from factory.

I don't believe it's possible without changing the firmware, If you have the unit and TTL serial hooked up first power up the unit and you should see the crystals listed there to confirm,

SA22C by Symmetricom, Inc., Copyright 2006
   SA22 Version 6.02C of 7/2006; Loader Version 3
   Mode CN41  Flag 0000  [5D68]ok

Unit serial code is XXXXXXXXXX-h, current tuning state is 6
Crystal: 60000000hz, ACMOS: 10000000.0hz, Sine: 10000000.0hz
Ctl Reg: 0000, Res temp off: -1.6261, Lamp temp off: -2.0584
FC: enabled, Srvc: low

Name00, did you buy from hamradiomarket? They claim all their modules are tested.

No, I got mine from a e-recycler that gets them sporadically and removes them from base stations.  I tried to convince him to give me the cables and heat sink mount, he wanted way too much for those, so I ended up building an adapter from 1.0mm headers, solder and shrink wrap, version 2 involved getting 1.0mm hole pitch breadboard, ethernet cable, and  DC-DC 15v to 5v, and soldering to secure the ethernet cable as my trace, primitive but usable.

most of the Rb module just comes from CDMA base station, but SA.22C and X72 are not, since the strange interface of SA.22C, the price of SA.22C is cheap, I am design a mechanical adapter for it, in orfer to use the SA.22C for replace X72 and LPRO, and I will design 2 PCB for the SA.22C.

I also noticed ebay now has pre-made boards from the "famous" BG7TBL (for those from familiar with his counters  and GPSDO).    I've ordered one and will test.

[Name00]

I decided to make it a separate post.

Some updates, I still have not been able to get my unit to output 1 pps, I ended using a picdiv to do this for sync from GPS pps then driven from the 10MHz from the SA.22C.

Second I've gotten the unit partially tuned to the GPS.  it's an involved process but will outline for anyone interested, I now have 3 unit totally in-sync with a small deviation but drift between them at about  7ns per 18 hours based on my scope (1 unit tuned below to the GPS and the other tuned to the pps of the first unit using picdiv).

Steps used:

1) Get LH 6.14, a GPS that outputs a PPS, a terminal software (putty?) for com access and of course a ttl - serial and interface working for the unit.
2) Use a very stable GPS module (I've used the "Huawei" GPS modules both the ublox LEA-8T and the trimble -- the trimble one is far superior as it actually does it's survey automatically and synthesizes the pps! while you need to manually tune the ublox and it's PPS will vary to the GPS signal quality)
3) start up your terminal software, set the control register to 0 (it enables everything) and exit
4) Make sure the SA.22C has been running for  at least 6 hours
5) Start lady heather, set the com port and issue /rxsa (/rxsb if confirm a non 60Mhz crystal??).
6) issue "&" then "a" in lady heather, and give it a period of 12 hours (43200)
7) let it run and complete note what it's set the DDS to, if you have any value at e-13 leave it there's no point it's already as good as it gets based on it's spec sheet..
if you have e-12 or worst (ie anything at e-11, e-10, or e-9), take the first set of numbers so let's say -5.1234e-10.  take that and do -5.1234 x 10^(12-##) so in this example -512.34
9) start up the terminal software
10) set the dds to 0 (f then 0)
11) set the dds to the value from 7 (from example f then -512.34)
12) save  (t and 5987717)
13) exit terminal software, repeat 5 to 12, until your last 2 reading are e-12 or you get a e-13, and if you never get to 2 e-12 then your GPS pps has way too much variability.

Notes:
-- if you have a scope you can check it or if you have a GPSDO, you can also compare it to that to verify you've moved to the right direction and stability before doing step 12.
-- from what I can tell the t does save the f value on save, once saved the f value seems to be reset to 0 again, or I lucked out in my limited testing between 3 units split in the method above.
-- j command in the terminal software clearly shows it is tracking the pps (you can remove the source and see the value change).

[zrq]

Beware of this ebay seller: Comp-Electronics 4U Online. I got a SA.22c from them in "Used" condition, but it apparently never lock. Let's see how he/she responds to my message.