[time-nuts] HP5061B Peak to Valley Ratios

[Donald E. Pauly]

We are having trouble getting beam current on our #2 HP5061B.  Ion
current has gone down in a week from 10 to zero. It looks like the rf
chain is working normally.  Both HV power supplies had to repaired.
Beam current is all the way up and which gives 2 on the meter. We are
preparing to do the Low Frequency Coil test mentioned on page 5-22
section 5-175.

I got this idea from that procedure.  On our good #1 instrument we set
the beam current at 20 with normal lock.  The middle coax J2 which
carries 12.631 mc to the harmonic generator was removed next.  The
beam current instantly dropped to 2.  We set the beam current with the
front panel control at 10 to 30 and all three settings dropped about
10 to one when the cable was pulled.  This ratio seems to be a good
indicator of beam tube quality.  I don't see it in the manual, but the
fine five turn pot oscillator control works much better than the
course adjustment for setting peak beam current.  It also works better
for setting the control voltage to zero.  The push to turn course
frequency control slot has been chewed up by the previous owner.

We are planning to get an oscilloscope display of the main and
secondary lobes similar to page 4-31 Figure 4-43.  If it works we will
post it.  It should show both the dc and ac parts of the beam current
as the 137 cps sweep goes from one extreme to the other.  Will anyone
having any experience with the Low Frequency Coil test kindly post on
the subject?  This is NOT the Zeeman frequency test.