I have had two 10811 with EFC problems that turned out to be lack of soldering of one internal joint. This is a large PTFE ferule with several leads including the varactor and trimmer going into it. For many years the leads all contacted but finally one lead developed an oxide film. A soldering iron fixed them very quickly. The serial numbers were widely separated, so it was not an unlucky batch problem. cheers, Neville Michie
On 16/11/2012, at 1:57 PM, Chris Howard wrote: > > You all were right, my targeting of the 50 ohm resistor > across the oscillator output does not seem to have solved the > problem. A good thing to do, probably, but not the answer. > > While I was all excited about the resistor change I also > mapped out the control voltage (EFC) vs frequency change. > I wrote it out but didn't pay much attention. Now > I've been pondering over that a bit. My next theory > is that my EFC maybe isn't really doing very much. > > First I need to know if I am reading this right. > My frequency counter is a Racal 1992 It reads > 9.99999997^6 as I write. A total of 9 digits > with a smaller "6" to the right. > > If I read this correctly, I'm looking at > 9,999,999.97 Hz ? If so, then I've got an EFC problem. > > My EFC mapping looks like this (this was done before > I adjusted the coarse control) > > > -4.94 VDC 9,999,999.95 > -3.70 9,999,999.95 > -1.24 9.999.999.93 > 0 VDC 9,999,999.93 > +1.21 9,999,999.92 > +2.44 9,999,999.92 > +3.67 9,999,999.91 > +4.90 VDC 9,999,999.90 > > It doesn't look to me like I am getting anything > like 1/2 hertz range using the EFC. If that's > the case than my controller card is frantically > steering but not getting the desired result. > > Or, if I'm reading it wrong, maybe that last digit > is 0-5 meaning 1/2 a hertz and I am all wet (again). > > This particular oscillator came out of an old HP counter > and I believe the EFC was wired to ground. So maybe > the thing has never been exercised. Are there versions > of the 10811 that don't have EFC guts inside? > > Hope I'm not boring you all to death. > > Chris > w0ep > > > > On 11/9/2012 11:26 PM, WarrenS wrote: >> Chris >> >> HP 10811 can't drift that much that fast unless something is near broken, or >> being connected wrong like gnds or PS voltage. >> Check the operation of the oven. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
