Hello Time-Nuts, I opened the LPFRS and removed the 4 electrolytic caps. One was completely dead. After I swapped them to new ones, everything worked fine. The phase ripple disappeared, the unit is now on par with the second one (or beyond my measurement capabilities...). So, I highly recommend this to every owner of a used LPFRS - it takes about 10 minutes. Thanks again for all the hints and have a nice weekend, Matthias Am 25.05.2017 um 12:46 schrieb Bob kb8tq: > Hi > > >> On May 25, 2017, at 4:12 AM, Matthias Jelen <Matthias.Jelen@gmx.de> wrote: >> >> Hi Angus, >> >> thanks for the hint. I read through this fairly long thread - the baseline seems to be: Replace the caps. >> >> Best regards, >> >> Matthias > > That’s what worked for mine ….. (at least most of them). In my case they arrived dead. > > Bob > >> Am 23.05.2017 um 21:44 schrieb Angus: >>> Hi, >>> >>> If you've not already looked, it would be worth checking on the >>> EEVblog since there were some discussions there on faults in these >>> units - particularly the capacitor and lamp voltage issues. >>> One of the temperature controllers could be a little unstable too. >>> >>> Angus. >>> >>> >>> On Tue, 23 May 2017 09:40:26 +0200, you wrote: >>> >>>> Hello Time-Nuts, >>>> >>>> i´ve been playing with some Rbs recently. >>>> >>>> I compared two LPFRS-01 to a PRS-10. One seems to behave quite well (compared to the specs given here: http://www.spectratime.com/uploads/documents/isource/iSource_LPFRS%20Spec.pdf) - short term stability specs are met), the other one shows quite some phase ripple (appx. 1 ns RMS with a frequency around 0.007 Hz) which spoils ADEV in the 60 - 200s range, very similiar to the typical GPSDO bump. Long term stabilty is OK. >>>> >>>> Unfortunatly I didn´t find any schematics on the web. Has anyone encountered a similiar problem with this unit? Any idea were this might come from? My first guess would be a problem in the control loop locking the VCXO to the Rb, but I have no clue which time constants are used in the PLL. >>>> >>>> Any hints are appreciated. >>>> >>>> Regards, >>>> >>>> Matthias >>>> >>>> _______________________________________________ >>>> 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. >>> _______________________________________________ >>> 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. >>> >> _______________________________________________ >> 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. > _______________________________________________ > 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. >