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.je...@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
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