[time-nuts] Troubleshooting an HP 58503A
Matthew D'Asaro
medasaro at mit.edu
Sun Oct 14 04:21:26 UTC 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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