Agilent Technologies 8590L Service Manual page 431

Analyzer Options and Block Diagrams
First LO Distribution Amplifier (LODA) 8593E, 8594E, 8594Q, 8595E, 8596E Option 009
IS THE TEST SIGNAL AT THE PROPER LEVEL?
Comments
Preamplifer ON
432
TREE 5: Average Power Test Problems
Problems/Reasons
If the problem appears with the
preamplifier ON (PREAMP ON
OFF, ON is underlined) the root
cause is likely to be the
preamplifier or the preamplifier
control.
Diagnostic/Fix Action
1. Evaluate the preamplifier. Refer
to "Set up to use the preamplifier" in
the "Making Measurements"
chapter of the user's guide for your
QAM analyzer.
a. Remove the 8770 test signal,
then apply the CAL signal to
the RF input.
b. Do the "Measuring the
Preamplifier Gain" procedure
to find out what suspect
preamplifier gain truly is. It
should be 23 ±3 dB. If it is
not, the problem is in the
preamplifier.
c. Test the preamplifier control
by turning the preamplifier
on and off, using
.
OFF
2. If you cannot control the
preamplifier, the problem is in the
preamplifier control board. Swap
the preamplifier control board with
a "known" good board.
3. If the problem persists, replace
the DSP with a "known" good board.
Rerun the test to see if it passes. If
so, save the bad board and the
matching test data for division
analysis.
4. If swapping the DSP does not
work, perform an analyzer self
calibration. Troubleshoot as a
spectrum analyzer platform
problem if it does not pass.
PREAMP ON
Chapter 10