[time-nuts] Z3805A GPS module going deaf, what modules can replace it?

Mike Cook michael.cook at sfr.fr
Fri Feb 13 21:05:21 UTC 2015


The model number is that of an Oncore VP. It is easy to remove the receiver from the unit for testing independently. That might be worth a try. Maybe reseating it may help if there is any continuity problem on the pins. Unfortunately you will probably need another VP to replace a dead one. IIRC, I did try to replace a VP in my Z3801A with a UT+ , but it would not work. 


"Ceux qui sont prêts à abandonner une liberté essentielle pour obtenir une petite et provisoire sécurité, ne méritent ni liberté ni sécurité."
Benjimin Franklin

> Le 13 févr. 2015 à 20:28, John Stone <johns at ks.uiuc.edu> a écrit :
> 
> Hi,
>  I've got a Z3805A that I bought off ebay a couple of 
> years ago, and it recently started going deaf, beginning
> with an apparent loss of sensitivity leading to holdovers, 
> and more recently, receiver errors reported in the system 
> status.
> 
> I have the Z3805A, a thunderbolt, and one of the recently discussed
> KS-24361 units sharing the same GPS antenna via a four output
> 58536A distribution box.  I've run the Z3805A on its own
> separate antenna and compared its signal levels with the
> other units, and it has clearly developed some issue.
> After a power cycle, I can get it going by initiating a
> survey, but after a day or two of running it will lose 
> all sats, and in some cases the status command will show
> "GPS Rcv: Err".
> 
> I queried the hardware info on the GPS in this unit and 
> from what I've gathered, it's one of the earliest motorola
> Oncore GPS receivers based on the "B1121P1114" model number.
> What GPS module models can I put into a Z3805A to get it 
> running again?  Any tips are appreciated, including suggestions
> for tests I could run on the GPS module, the power supply, or
> other items that might be common failure points.
> 
> I've included the output from scpi queries below, and the 
> status from the KS-24361 attached to the same antenna 
> for comparison:
> 
> *IDN?
> HEWLETT-PACKARD,Z3805A,3542A00943,3543B-A
> 
> :DIAG:LIF:COUN?
> +29437
> 
> :DIAG:IDEN:GPS?
> "COPYRIGHT 1991-1995 MOTOROLA INC.",
> "SFTW P/N # 98-P39972M     ",
> "SOFTWARE VER # 8          ",
> "SOFTWARE REV # 4          ",
> "SOFTWARE DATE  13 JUL 1995",
> "MODEL #    B1121P1114     ",
> "HDWR P/N # _              ",
> "SERIAL #   SSG0120281     ",
> "MANUFACTUR DATE 5M18      ",
> "OPTIONS LIST    IB        "
> 
> 
> Failing Z3805A system status output:
> ------------------------------- Receiver Status -------------------------------
> 
> SYNCHRONIZATION ........................................... [ Outputs Invalid ]
> SmartClock Mode ___________________________   Reference Outputs _______________
>   Locked to                                  TFOM     9             FFOM     3
>   Recovery                                   1PPS TI  --
>   Holdover                                   HOLD THR 1.000 us
>>> Power-up: GPS acquisition                  Holdover Uncertainty ____________
>                                              Predict  --
> 
> ACQUISITION .......................................... [ GPS 1PPS CLK Invalid ]
> Satellite Status __________________________   Time ____________________________
> Tracking: 0        Not Tracking: 0            GPS      08:51:14 [?] 12 Feb 2015
>                                              1PPS CLK Absent or freq error
>                                              ANT DLY  180 ns
>                                              Position ________________________
>                                              MODE     Survey:      0% complete
>                                                       Suspended: no track data
>                                              INIT LAT N  40:08:01.714
>                                              INIT LON W  88:12:27.166
> ELEV MASK 10 deg                              INIT HGT         +198.59 m  (MSL)
> HEALTH MONITOR ...................................................... [ ERROR ]
> Self Test: OK    Int Pwr: OK   Oven Pwr: OK   OCXO: OK   EFC: OK   GPS Rcv: Err
> scpi > 
> 
> 
> For comparison, here is what my recently acquired Z381x / KS-24361 GPSDO
> says, driven from the same antenna:
> 
> -------------------------- Secondary Receiver Status --------------------------
> SYNCHRONIZATION ............................................. [ Outputs Valid ]
> SmartClock Mode ___________________________   Reference Outputs _______________
>>> Locked to GPS                              TFOM     3             FFOM     0
>   Recovery                                   1PPS TI +10.0 ns relative to GPS
>   Holdover                                   HOLD THR 1.000 us
>   Power-up                                   Holdover Uncertainty ____________
>                                              Predict  3.7 us/initial 24 hrs
> 
> ACQUISITION ................................................ [ GPS 1PPS Valid ]
> Tracking: 8 ____   Not Tracking: 2 ________   Time _____ +1 leap second pending
> PRN  El  Az  C/N   PRN  El  Az                GPS      19:22:10     13 Feb 2015
>  1  23 302   37    11  15 278                GPS 1PPS Synchronized to GPS Time
>  4  32 269   43    18  18 138                ANT DLY  60 ns
> 12  20  49   38                              Position ________________________
> 14  66  30   46                              MODE     Hold
> 22  53 146   39                              
> 25  36  90   38                              LAT      N  40:08:00.925
> 31  61 216   42                              LON      W  88:12:26.995
> 32  43 310   46                              HGT              +200.94 m  (GPS)
> ELEV MASK 10 deg                              
> HEALTH MONITOR ......................................................... [ OK ]
> Self Test: OK    Int Pwr: OK   Oven Pwr: OK   OCXO: OK   EFC: OK   GPS Rcv: OK 
> 
> 
> Cheers,
>  John Stone
> 
> -- 
> NIH Center for Macromolecular Modeling and Bioinformatics
> Beckman Institute for Advanced Science and Technology
> University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
> http://www.ks.uiuc.edu/~johns/           Phone: 217-244-3349
> http://www.ks.uiuc.edu/Research/vmd/      
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