[time-nuts] Troubleshooting an HP 58503A
Matthew D'Asaro
medasaro at mit.edu
Sun Oct 14 04:20:47 UTC 2018
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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