Keysight Technologies Option 503 Service Manual page 187

RF Section Troubleshooting (Millimeter-Wave Analyzers)
Troubleshooting
The LO input at W20, and the LO outputs were tested when performing the
First LO Verification.
It is possible to measure the W48 input cable to the Switched Filter where it
connects to A13A2J2, and the output of the Switched Filter at W49 where it
connects to A13A1J11. The A13A2 Switched Filter is not separately
replaceable, but being able to determine where the signal level is faulty, can
aid in verifying the faulty assembly. See the block diagram for signal levels.
When measuring W48, the analyzer must be powered down and ribbon
cable W28 on the Switched Filter removed to gain access to W48. Once
the measuring spectrum analyzer is connected to W48, the W28 ribbon
cable must be reinstalled, and only then can the analyzer be powered back
up. The ribbon cable is fragile so it cannot be bent out of the way to access
the cable, and should not be removed and installed with power applied.
Electronic Attenuator Test (Option EA3)
The electronic attenuator is aligned as part of the System Gain internal
alignment process. See the description of the initial alignments and the
location of the alignment history file in the Boot Up and Initialization
Troubleshooting chapter. Viewing the Alignment History file will tell you if
other alignment tests failed, and reveal which electronic attenuator steps
failed.
To verify the electronic attenuator operation on instruments with Option EA3,
set up the analyzer to view the 50 MHz calibrator signal on screen. Press
Input/Output, RF Calibrator, 50 MHz, Center Frequency, 50 MHz, Span,
500 kHz
Press Peak Search to place a marker on the calibrator signal, then press
Marker Delta
Activate the electronic attenuator. Press AMPTD, Attenuation, Enable Elec
Atten. Then press Elec Atten.
Press the up arrow key to step through all attenuator steps while monitoring
the marker delta readout. The signal level should not change more than 0.4 dB
as indicated by the marker delta readout.
If the attenuator switches slowly, or the signal is not present when the
electronic attenuator is switched into the signal path or the signal appears only
when the attenuator is switched on, suspect the control signals from the A15
Front End Controller are faulty or the A13 Front End assembly is faulty. If the
attenuator switches, but the switching error between attenuator settings is
greater than ± 0.4 dB, assure that any other internal alignment failures are
resolved since the System Gain alignment must run before optimum
performance is possible. Assure you have evaluated all causes before you
replace the Front End assembly.
If you determine the problem is at a frequency other than 50 MHz, perform the
low band flatness adjustment before replacing the Front End assembly.
N9030A PXA Signal Analyzer Service Guide 187