Keysight Technologies N9040B UXA Signal Analyzer Service Guide 179
Front End Control Troubleshooting
A15 Front End Control Assembly Troubleshooting
Verifying SW3 (Option LNP only)
Since there is a ribbon cable from the A15J802 to SW3, it is not feasible to use
a voltmeter or oscilloscope to measure the control voltages. For testing SW3,
the “click” test can be used.
Press Mode Preset on the analyzer. Press FREQ, 5 GHz, SPAN, 1 MHz. Verify
the optional preamplifier is off by pressing AMPTD, Signal Path and verify the
Internal Preamp Low Band toggle is in the Off position. The Internal Preamp
toggle must be Off in order to test SW3. Press AMPTD, Signal Path, uW Path
Control, Low Noise Path Enable on the analyzer. You should hear a distinct
“click” noise from SW3 when the low noise path is selected. Now press uW
Path Control and select Standard Path. SW3 will “click” again and return to
the standard RF path.
Another way of testing this switch is using an RF signal. This is described in the
RF Section Troubleshooting chapter, under the high band troubleshooting
section.
Verifying SW1 and SW2 (Option MPB)
SW1 and SW2 can be verified three different ways:
—“Click” Test
— R.F. Signal Tracing
“Click” Test
This test changes between two different path modes. When this is done a
distinct “click” noise from SW1 and SW2 can be heard. Since both switches
switch at the same time, it is difficult to decipher if one is switching and the
other is not.
Press Mode, Preset on the analyzer. Press FREQ, 5 GHz, SPAN, 1 MHz,
AMPTD, Signal Path, uW Path Control. Standard Path is the default. Select
uW Preselector Bypass and you should hear a distinct “click” noise if the
control logic from the A15 Front End Control board is getting to SW1 and SW2.
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