HP Z3815A GPSDO - Page 1
Forum section: electronics / projects

author: shinjiikari0601
author_rank: Newbie
timestamp: July 05, 2016, 01:04:09 am
content: Hello all,I've recently started getting back into being a little bit of a time-nut, and have fired up my two HP Z3801A's for the first time in a few years. Was happy to see them obtain a lock and settle down quickly. Last week, I also had two new additions arrive; two HP Z3815A's. These are the raw cards, not the more friendly boxed versions that occasionally appear on various sites. I know the basics of these units... Power requirements and pins, GPS antenna connection, etc. I also understand the console port has a similar SCPI command set as the Z3801A's, which I am familiar with. I've heard that there is some unofficial documentation out there. My attempts to contact the author of said documentation has failed, with bounced emails to a couple addresses I was able to track down.Was curious if anyone had any experience with these, and if so, what you think of them, and any quirks you may have ran into (for instance, the Z3801A's have a bug which causes the OCXO status bits to get 'stuck' and can require a bit of prodding to get them back into a functional state). Also, what need drove you to start working with GPSDO's? Mine has always just been a curiosity in accurate time distribution, and I use them to synchronize devices via SNTP and NTP (I know, a lot of trouble to go through, when I could just point my NTP clients at one of the NIST NTP pools or similar providers).Thanks!

author: Vgkid
author_rank: Super Contributor
timestamp: July 05, 2016, 05:06:37 pm
content: @ unit 01I remember seeing some unoficial pin outs several years ago,but cannot find anything now. Try looking into the older /newer variants as well. Once you find the comms port, Lady Heather should work.

author: shinjiikari0601
author_rank: Newbie
timestamp: July 05, 2016, 11:23:59 pm
content: Thank you for the reply. I've tracked down some additional information last night, confirming the pinout information I had seen floating around the net, and expanding upon it a bit. Looks like there's still a lot of unknowns about the unit, particularly the purpose of a large number of the PECL pairs on the main connector. However, the main 'important' signals have all been documented. Planning on ordering a new Rigol scope this week... Maybe researching some of the unknowns of these units and perhaps being able to contribute a bit of knowledge back to the community could be a good way to get to know the Rigol I am looking at.Would also like to see if I can get a dump of the firmware from one of the units. Maybe I could extract the strings at least, and make sure all the SCPI commands are accounted for.Anyway, thanks again for the input!

author: shinjiikari0601
author_rank: Newbie
timestamp: July 06, 2016, 12:54:15 am
content: Finally powered up my two Z3815A's... Looks like one of them is as happy as a GPSDO can be whilst not tracking satellites (haven't made the antenna adapter pigtail yet):Code:scpi > :SYST:STAT?[ Unlocked ] ------------------- GPSR 2 Status --------------------------------SYNCHRONIZATION ........................................... [ Outputs Invalid ]SmartClock Mode ___________________________ Reference Outputs _______________Locked TFOM 9 FFOM 3Recovery 1PPS TI --Holdover HOLD THR 1.000 us>> Power-up: GPS acquisition Holdover Uncertainty ____________Predict: --ACQUISITION .............................................. [ GPS 1PPS Invalid ]Tracking: 0 ____ Not Tracking: 0 ________ Time ____________________________GPS 00:10:56 [?] 01 Jan 1994GPS 1PPS Invalid: not trackingANT DLY 0 nsPosition ________________________MODE Survey: 0% completeSuspended: track <4 satsINIT LAT N 34:44:00.000INIT LON E 135:21:00.000INIT HGT +0.00 m (MSL)ELEV MASK 10 degHEALTH MONITOR ...................................................... [ ERROR ]Self Test: OK Int Pwr: OK Oven Pwr: OK OCXO: OK EFC: OK GPS Rcv: OKAlarms: Antennascpi >My second unit, well, it's not nearly as happy :-/Code:scpi > :SYST:STAT?[ ALARM ] ---------------------- GPSR 2 Status --------------------------------SYNCHRONIZATION ........................................... [ Outputs Invalid ]SmartClock Mode ___________________________ Reference Outputs _______________Locked TFOM 9 FFOM 3Recovery 1PPS TI --Holdover HOLD THR 1.000 us>> Power-up: GPS acquisition Holdover Uncertainty ____________Predict: --ACQUISITION .............................................. [ GPS 1PPS Invalid ]Tracking: 0 ____ Not Tracking: 0 ________ Time ____________________________GPS 00:14:28 [?] 01 Jan 1994GPS 1PPS Invalid: not trackingANT DLY 0 nsPosition ________________________MODE Survey: 0% completeSuspended: track <4 satsINIT LAT N 34:44:00.000INIT LON E 135:21:00.000INIT HGT +0.00 m (MSL)ELEV MASK 10 degHEALTH MONITOR ...................................................... [ ERROR ]Self Test: OK Int Pwr: Err Oven Pwr: OK OCXO: Err EFC: OK GPS Rcv: OKAlarms: OCXO, Power, 10MHz, 19.8MHz, 19.6608MHz, Antennascpi >Had a feeling that I'd be lucky if one out of two of them was usable. Was hopeful, but I guess the realistic part of me wasn't holding my breath....Guess I'll start poking around some, to see if its perhaps a power supply issue, or some other repairable cause.Thanks!

author: Vgkid
author_rank: Super Contributor
timestamp: July 06, 2016, 12:58:51 am
content: @ unit -01:Do both units look the same?On the Time-Nuts mailing list, it looks like there several similiar units floating around. I assume that was your post on the TN list, today.

author: shinjiikari0601
author_rank: Newbie
timestamp: July 06, 2016, 01:55:15 am
content: Vgkid,Yes, twas I. I've been a long time lurker on the list. Recently re-subscribed.They are both the HP units, not the CIC units. Both the raw cards, not the packaged versions.Spent a few minutes probing around just now, and it appears I've got a power supply issue in the second unit. There's a couple test points, which are near zero on the bad unit, while hanging near -13VDC and +15VDC on the good unit.Output from the error log:Code:Log 098:20101101.00:00:00: Power onLog 099:20101101.00:00:01: Self-test failedLog 100:20101101.00:00:01: 19.6608 MHz FailLog 101:20101101.00:00:01: 19.8 MHz FailLog 102:20101101.00:00:01: 10 MHz FailLog 103:20101101.00:00:01: Selftest FailLog 104:20101101.00:00:04: 12A is out of tolerance, value: 0.85Log 105:20101101.00:00:04: Power FailLog 106:20101101.00:00:05: 12C is out of tolerance, value: 0.26Log 107:20101101.00:00:05: -12A is out of tolerance, value: -6.08Log 108:20101101.00:00:05: -12C is out of tolerance, value: -6.06Log 109:20101101.00:00:05: -12E is out of tolerance, value: -6.08Log 110:20101101.00:00:08: Internal OCXO FailI will tear the unit down further in the next few days, to trace the PSU further. Nice to have a working unit to compare against, though. Its obvious that part of the power supply is working fine, given the uC and associated components are booting up enough to communicate, perform self tests, and indicate failure on the front panel LED's.Maybe once I get the PSU issues sorted out, the rest of the errors will vanish... Assuming I've not already done permanent damage by running it in this state. I have pulled the OXCO module for now so that any voltage surges or other power issues don't fry it (if its not already).Thanks!