Agilent Technologies 8752C, Service Manual, Page: 280 / 510

Phase Lock Diagnostic Routines
P erform the following steps to determine at what frequencies and bands the
phase lock problem occurs .
1.
Press 4
PRESET
5 4
SYSTEM
5
N
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
SERVICE MENU
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
SERVICE MODES
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
PLL AUTO OFF to
switch o the automatic phase-locked loop . Normally , when the phase-locked
loop detects lock problems , it automatically aborts the sweep and attempts to
recalibrate the pretune cycle . Switching o PLL A UTO defeats this routine .
2.
Press
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
PLL DIAG ON to switch on the phase-locked loop diagnostic service
mode . In this mode , the phase lock cycle and subsweep number are displayed
on the analyzer display . (See \Service modes menu" in the \Service Key
Menus and Error Messages" chapter for more information.)
3.
Press
N NNNNNNNNNNNNNNNNNNNNNNNNNNNN
PLL PAUSE to pause the phase lock sequence and determine where the
source is trying to tune when lock is lost.
Refer to \Source theory" in the \Theory of Operation" chapter for additional
information regarding band related problems . Then use the procedures in this
chapter to check source functions at specic frequencies .
Broadband P ower Problems
This section assumes that a power problem exists across the full frequency
range , but that no error message is displayed on the analyzer . The problem will
only eect the reection test port. Assemblies in question include:
A3 source
A30 dual directional coupler
any cables from the A3 source to the output of the reection test port
7-40 Source T roubleshooting