180 Keysight Technologies N9040B UXA Signal Analyzer Service Guide
Front End Control Troubleshooting
A15 Front End Control Assembly Troubleshooting
RF Signal Tracing
Refer to Chapter 4, “RF Section Troubleshooting (RF/Microwave Analyzers)”
for this method of troubleshooting if you are unable to use an Oscilloscope
Verifying Narrowband IF Out (A15J900)
The outer cover and top shield need to be removed to verify A15J900 I.F.
output to the A2 Analog IF assembly. Refer to Chapter 15, “Assembly
Replacement Procedures” for the removal procedure. Press MODE/MEAS,
Spectrum Analyzer, OK, Mode Preset on the analyzer. Press Input/Output, RF
Calibrator, 50 MHz, FREQ, 50 MHz, Span and toggle from Swept Span to Zero
Span. Press Amptd, Attenuation, 10 dB, Amptd, Signal Path and verify
Internal Preamp Low Band toggle is set to Off. Press System, Alignments,
Auto Align and choose Off from the drop-down menu. Disconnect the cable
marked J900 that plugs into the top of the A15, Front End Controller board and
connect a functioning spectrum analyzer where the cable was plugged in.
J900's output should be 322.5 MHz at ~-20 dBm on the functioning spectrum
analyzer if the Front End Controller board is switching this level correctly. If -20
dBm is not being measured correctly, remove the cable labeled J902 from the
Front End Controller board and measure the output of that cable. This should
also measure 322.5 MHz at ~-20 dBm. If the output of the J902 cable
measures correctly and yet the output of J900 is incorrect, the most probable
cause is the A15, Front End Controller board.
Reconnect all cables to their correct location when finished with the
measurements.
IMPORTANT When plugging in an mmcx connector, a distinct “snap” should be heard
when the cable is seated correctly.
Verifying Aux IF Out, Rear Panel (Option CR3, CRP, ALV only)
The Aux I.F. output connector on the rear panel of the UXA is installed on each
instrument; however the actual Aux I.F. output frequency will vary depending
on the options installed. These options are all enabled with a license key. The
first step in verifying the Aux I.F. output is the make sure the option is licensed
by pressing System, Show, System on the analyzer and make sure the option
identifies itself in the table.
The I.F. switch path and frequency generation occurs on the A15, Front End
Controller board. This troubleshooting procedure provides the instrument
setups to verify options CR3, CRP and ALV. Test the Aux I.F. output based on
the options installed in the analyzer.
Standard UXA
No test to perform.
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