David, David I. Emery skrev: > On Mon, Mar 23, 2009 at 04:17:00PM -0400, phil wrote: >> Firmware for that vintage is out of the question now. It is my understanding >> that newer receiver boards solved that issue. My question, could some newer >> generic receiver module be programmed/interfaced to replace that board? I >> don't have a component level manual on that receiver. > > > I have a 9390 with Rb - currently in deep retirement - that I > acquired in 2000. It locked OK after I repaired the 16.368 MHz oscillator > lock circuit, but had the rollover date problem.
What magical GPS week number did we just hit? http://www.ngs.noaa.gov/CORS/Gpscal.html The time of failure matches the entering of GPS week 1524. This is an interesting number as it is exactly 1024 + 500. 500 seems like an fairly arbitrary GPS week number to use as a base number. It matches... 1989-08-06: http://csrc.ucsd.edu/scripts/convertDate.cgi?time=0500+0 So the magic GPS week roll-over bias is now known for these. > I eventually was given a small PIC microcontroller based adapter > card from a defunct 9390 someone else owned that went between the Trimble > GPS board and the Datum mother board and fiddled the serial data > messages from the GPS to correct the GPS date (as I remember it, it > added the leading 1024 bit in a 16 bit field). This corrected the date > so it read correctly. > > This Datum mini board was apparently at least one of the fixes > that Datum provided customers for the GPS date rollover bug - there may > also have been some updated firmware for the motherboard, I forget. Strange option to make a separate board rather than modify the firmware. > I did disassemble the PIC code, but what I did with the results > I forget... other than decide what the board did to the data stream. > > I did have a copy of the schematic and a user manual for the Datum > 9390 I got from Symetricomm/Datum - this definitely did NOT include much > info on the Trimble GPS board and as I remember it the manual didn't > match the firmware I had all that well nor did the schematic match > the hardware I had exactly either. Wohooo! >> I too have a couple of those units that we use simply for the disciplined >> rubidium 10 meg out even though the week and year is and has been off for >> some time. >> Phil > > I guess it is time to look up the GPS date in weeks and see how > close to the next rollover it is... > Can be any week now... but week 1536 (1024 + 512) seems like a likely arbitrary week like anyone... Maybe it is time for me to get a GPS L1 tester... Cheers, Magnus _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.