Agilent Technologies HP 8719D Service Manual page 293

Ext I&f
13. (Rear panel external reference input)
This node is used to detect an external reference voltage. If an external
reference (timebase) is used, the voltage level should be about -0.6V. If an
external reference is not used, the voltage level should be about -0.87V.
100
14.
Counter ON: analog bus
Reading: .100 MHz
This node counts the Al2 100 kHz reference signal that is used on Al3
(the fractional-N analog assembly) as a reference frequency for the phase
detector.
VCO
15. Tune (Al2 VCO tuning voltage)
This node displays the tuning voltage for the Al2 VCO. It is used in the
reference assembly VCO tune adjustment.
16. LO (2nd converter reference)
Counter ON: analog bus
Reading: 9.996 MHz
This node counts the 2nd LO used by the 2nd converter assemblies to
produce the 2nd IF of 4 kHz.
PL Ref
17. (Phase lock reference)
Counter ON: analog bus
Reading: 1 MHz
This node counts the reference signal used by the phase comparator circuit
on the All phase lock assembly.
VCXO Tune (40 MHz
18.
This node displays the voltage used to fine tune the Al2 reference VCXO to
40 MHz. You should see a flat line at some voltage level (the actual voltage
level varies from instrument to instrument). Anything other than a flat
line indicates that the VCXO is tuning to different frequencies. Refer to
the frequency accuracy adjustment in the "Adjustments and Correction
Constants" chapter.
1 O-34 Service Key Menus and Error Messages
VCXO tuning voltage)