[time-nuts] 5061A Setup Questions

[Chris Hastreiter]

Hi All,



I’m currently working on combining a 5061A chassis with a 5061-6077 beam
tube that I acquired and I have a few questions I’m hoping this group can
help me with.  As background, my 5061A is a later model with serial number
prefix 2506A (originally built with options 001 and 004).  The beam tube is
from a 5061B.  I have the 05061-9052 and 05061-99001 manuals, but as my
unit is a later build it seems to have more in common with the 5061B
manual.  It looks like the 05061-9068 manual would be closer to my build,
does anyone have a PDF of that manual they’d be willing to share?



*A11 Cesium Oven Heater Setup*



The A11 assembly I have is 5061-6144 Series 2506 and is currently
configured for the high performance beam tube.  I see that I need to change
R6, R14, and R15 to work with the -6077 tube but one thing I noticed is
that R6 is currently 2.6k whereas the manual says it should be 4.3k for the
high performance tube.  Are there any changes or considerations I should be
aware of for R6 or should I simply use the 43.0k value specified in the
manual for standard performance?



I also noticed that there are what appear to be two thermocouple wires
coming out of silicone strain relief on the 5061-6077 tube.  These do not
appear in any manual as far as I can tell.  Does anyone know what they are
for?



*A15 C-Field Current Source*



I see that I need to change R21 from its current value of 310Ohms to
205Ohms to convert the unit for a standard beam tube.  However, this is
marked as a selected value component and the manual references this as a
part that would have come with the tube in the replacement procedure.  Does
anyone have a measurement for what the C-Field current should be in case I
need to tweak this value to get in the right range?



Also, from the archives of this list I see that the 5061 has been built
with two different zeeman frequencies corresponding to two different
synthesizer frequencies:



·         42.82kHz with 12.6317716MHz Synth

·         53.53kHz with 12.6317725MHz Synth



I have the 5061-6158 Series 2248 Synthesizer module and the 5061-6150
Series 2248 A15 module.  From that can I determine which synth frequency it
was designed for?  Alternatively, my plan was to reference a counter to the
5MHz output of the unit and count the synthesizer output to make a
determination.  Is there any problem with that approach?



*Electron Multiplier Voltage*



The 5061A manual discusses electron multiplier voltage in terms of setting
the voltage to match the marking on the tube and making ongoing adjustments
of the loop gain to achieve correct beam current / second harmonic
readings.  The 5061B manual, however, has the operator adjusting the
electron multiplier voltage throughout the life of the tube to maintain the
desired beam current.



Since the A15 module I have is the later design the circuit matches that of
the 5061B, but the adjustment potentiometer is on the PCB and not the front
panel.  I’m considering moving this to the front panel and adding the
necessary wiring so that I can set the electron multiplier voltage
according to the 5061B procedure.  Are there any other differences between
the 5061A and 5061B that I should be aware of that affect how the electron
multiplier voltage is set?



Thank you all for your help,



Chris