The OCXO is powered from the 5V rail of the UCCM, so I wonder how a Vref=5V would work? A bit of headroom wouod be required to make a reference circuit work.?
Wilko > On 23 Dec 2021, at 18:15, Bob kb8tq <kb...@n1k.org> wrote: > > Hi > > It’s a pretty good bet that the Vref is 5V > > Bob > >> On Dec 23, 2021, at 8:42 AM, Wilko Bulte <wilko.bu...@xs4all.nl> 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 -- time-nuts@lists.febo.com -- To unsubscribe send an >> email to time-nuts-le...@lists.febo.com >> To unsubscribe, go to and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an > email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.