Hi It’s a pretty good bet that the Vref is 5V
Bob > On Dec 23, 2021, at 8:42 AM, Wilko Bulte <[email protected]> wrote: > > hi, > > I am currently trying to revive a Trimble UCCM-LPS ex-telco GPSDO. > The model is a 57963-D according to the PCB silkscreen. > > Got the board without its OCXO but luckily my stash of surplus I have > discovered a Trimble OCXO labeled 72345-86. Given that that OCXO also has a > label UCCM-LPS it "should work". > > Joining the two resulted in: > > UCCM >syst:status? > > ------------------------------------------------------------------------------- > 57964-86 serial number S35DB68332 firmware ver 1.0.0.1-01 Ext > mode > ------------------------------------------------------------------------------- > Reference Status __________________________ Reference Outputs > _______________ > XX Ext Ref : [LOS] > TFOM 2 FFOM > 3 > UCCM A Status[OCXO WARMUP] > >>> GPS: [phase:-2.8E-09, settling] > ACQUISITION ...................................................[GPS 1PPS > Valid] > Tracking: 8 ____ Not Tracking: 3 ________ Time > ____________________________ > PRN El Az C/N PRN El Az GPS 13:28:51 23 Dec > 2021 > 15 71 212 37 5 6 195 > 24 45 272 43 30 7 85 ANT DLY 77 ns > 17 28 97 37 19 19 124 Position > ________________________ > 13 55 140 38 MODE Hold > 14 39 58 39 > 23 33 291 44 LAT N 51:xxx > 10 17 324 40 LON E 5:xxx > 12 7 212 34 HGT +27.54 m > (MSL) > > > > > ELEV MASK 5 deg > ------------------------------------------------------------------------------- > > Command complete > > Unfortunately it never went GPS locked. Longer story short: the pin of the > OCXO that (I think) should produce a Vref for the EFC circuitry produced > some random ~ 266mV. > > A quick experiment learned that the OCXO freq responds to the EFC voltage. > So, looks like the Vref circuit in the OCXO has died. > > Now the question: has anyone a working unit that they can measure the > correct Vref voltage from? > > For now I have fitted a 2.5V LM336 vref and I > see the EFC voltage go up and down a bit, with the output freq hovering > around 10MHz (+/- 4mHz roughly). > > tia, > Wilko > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe send an > email to [email protected] > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
