Keysight Technologies N9040B UXA Signal Analyzer Service Guide 243
Hardware Options
A21 Wideband Analog IF Troubleshooting
Verify the J18 Output
The J18 output is active only when the 40 MHz IF path is selected.
The following test can be used to assure the W41 cable and the switch on the
A21 Wideband AIF are good.
1. To select the 40 MHz IF path, press Meas Setup, IF Path. Tap IF Path and
choose 40 MHz from the drop down menu.
2. Turn on the 50 MHz calibrator as explained in the last section. Set the
center frequency to 50 MHz. Set the span to 0 Hz.
3. Connect A21J18 to a known good spectrum analyzer. Tune the spectrum
analyzer to 250 MHz. This port switches the 250 MHz IF that is input to the
A21 Wideband Analog IF to be routed to the A3J15 40 MHz Digital IF. If
this −23 dBm ±3 dB signal is present, you have verified the 250 MHz IF
from the A15J901 Front End Controller. If this signal is not present, verify
the signal is present on A15J901 of the A15 Front End Controller.
Verify the 2400 MHz Frequency Reference
1. Turn the instrument off.
2. Remove the instrument cover. Refer to Chapter 15, “Assembly
Replacement Procedures” in this service guide.
3. Turn on the signal analyzer and wait for the instrument to complete the
boot up process.
4. Press System, Alignments, Auto Align, Off.
5. Press Mode/Meas, IQ Analyzer, Complex Spectrum, OK.
6. Press Input/Output, RF Calibrator, 50 MHz
7. Press Meas Setup, IF Path. Tap IF Path and choose 255 MHz or 510 MHz
from the drop down menu.
8. Verify the 50 MHz signal is at −25 dBm on the analyzer display by pressing
FREQ, 50 MHz, SPAN, 1 MHz, Peak Search on the analyzer. The marker
readout should be 50 MHz at −25 dBm ±3 dB. If this reference signal is
measuring incorrectly, see Chapter 4, “RF Section Troubleshooting
(RF/Microwave Analyzers)” in this service guide.
9. Connect a known good spectrum analyzer to A21J3. Verify reference
signal at 2400 MHz at a level of + 9 dBm.
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