[time-nuts] Troubleshooting an HP 58503A

Matthew D'Asaro medasaro at mit.edu
Sun Oct 14 00:21:26 EDT 2018


It just locked!

-Matthew

On 10/13/2018 09:20 PM, Matthew D'Asaro wrote:
> All -
>     I think I have it fixed! The problem was a broken wire inside my 
> genuine HP 58532A antenna. I was suspicious of the antenna because it 
> didn't seem to matter if I had it connected or not - the 58503A 
> behaved exactly the same. I confirmed my suspicions by measuring the 
> DC current it drew. Zero. Something was wrong so I took it apart and 
> measured the resistance between the center conductor and the board and 
> found it to be infinity. As it turns out the center conductor of the 
> micro-coax that connects the N-connector to the board had broken right 
> where it was soldered on. It took a bit to figure out how to press the 
> center conductor out of the connector, reattach the coax, and press it 
> back in. To press it out I first had to unsolder the shield of the 
> coax and then I could use the back of a drill-bit placed in a vice to 
> force the center conductor out of the insulator. Once I had the cable 
> reattached, I could press it back in by placing it over the center 
> contact of a male N-connector and then screwing the two together. See 
> the attached pictures.
>
>     Anyway, once I had the antenna repaired it found satellites to 
> track immediately - I didn't even have to set an initial date or 
> location. It is about 2% of the way through its survey now and 
> hopefully will have locked in by morning.
>
> Thanks to all of you for your help!
>
> -Matthew D'Asaro
>
> On 10/13/2018 05:39 AM, Azelio Boriani wrote:
>> Try a SYSTem:PREset first, before sending the GPS:INITial.
>> On Sat, Oct 13, 2018 at 8:44 AM Matthew D'Asaro <medasaro at mit.edu> 
>> wrote:
>>> All -
>>>       I have made substantial progress on my HP 58503A, but I am not
>>> quite there yet. By watching the internal lights and the data on the
>>> processor bus I could see that the CPU was starting to boot and then
>>> restarting every ~15 seconds. Furthermore, the reset circuit didn't 
>>> seem
>>> to be working right. Sometimes when I power cycled it the front panel
>>> lights would flash to indicate a self-test, other times they would not.
>>> This seemed to indicate that the system was not being reset 
>>> correctly on
>>> start-up. More telling, when I manually triggered the reset generator
>>> chip, the system would not ever flash its front panel lights even 
>>> though
>>> I could see that the CPU was being reset per the internal lights.
>>>
>>>       The problem, as it turned out, was more mechanical than 
>>> electrical.
>>> As shown in the attached photo, someone had put the case back together
>>> with a screw that was too long! It dug into the board and cut two
>>> traces, one of which was the reset line for the UART chip (and probably
>>> some other chips as well - I didn't fully trace the line). Once I
>>> repaired these two traces (red wires in my picture) it booted right up
>>> and even passed its self-test!
>>>
>>>       However, the story does not end there. I now have it booting and
>>> appearing to "work" but I can't get it to track satellites. I manually
>>> set the location, date, and time with the following commands:
>>> GPS:INIT:DATE (date)
>>> GPS:INIT:POS (position)
>>> GPS:INIT:TIME (time)
>>>
>>>       I then setup the unit (inside, but with the GPS antenna near a
>>> window) and left it turned on overnight. However, no dice. The system
>>> does not display errors but won't track any satellites. Here is the
>>> results of a SYSTEM:STATUS? command:
>>>
>>> scpi > system:status?
>>> ------------------------------- Receiver Status
>>> -------------------------------
>>> SYNCHRONIZATION ........................................... [ Outputs
>>> Invalid ]
>>> SmartClock Mode ___________________________   Reference Outputs
>>> _______________
>>>      Locked                                     TFOM 9             
>>> FFOM     3
>>>      Recovery                                   1PPS TI  --
>>>      Holdover                                   HOLD THR 1.000 us
>>>   >> Power-up: GPS acquisition Holdover Uncertainty ____________
>>>                                                 Predict  --
>>>
>>> ACQUISITION .............................................. [ GPS 1PPS
>>> Invalid ]
>>> Tracking: 0 ____   Not Tracking: 14 _______   Time
>>> ____________________________
>>>                      PRN  El  Az  PRN  El  Az   UTC 05:08:22 [?] 11 
>>> Oct 2018
>>>                      * 1  -- ---  *10  -- ---   GPS 1PPS Invalid: not
>>> tracking
>>>                      * 2  -- ---   16  35  50   ANT DLY  0 ns
>>>                      * 3  -- ---  *23  55 129   Position
>>> ________________________
>>>                      * 5  -- ---   26  10  41   MODE Survey:      0% 
>>> complete
>>>                      * 6  -- ---   27  21  96 Suspended: track <4 sats
>>>                        7  57 267   30  25 257   INIT LAT N 47:42:01.770
>>>                      * 8  13 127                INIT LON W 
>>> 122:16:26.770
>>>                        9  81 141                INIT HGT          
>>> +20.00
>>> m  (MSL)
>>> ELEV MASK 10 deg   *attempting to track
>>> HEALTH MONITOR 
>>> .........................................................
>>> [ OK ]
>>> Self Test: OK    Int Pwr: OK   Oven Pwr: OK   OCXO: OK EFC: OK   GPS
>>> Rcv: OK
>>> scpi >
>>>
>>> Is there anything else I can try?
>>>
>>> Thanks in advance,
>>> Matthew D'Asaro
>>>
>>> On 10/07/2018 12:26 AM, Mark Sims wrote:
>>>> The 58503A needs a null-modem pinout serial cable to connect to a 
>>>> PC. The baud rate defaults to 9600:8:N:1
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