220 N9030B PXA Signal Analyzer Service Guide
Front End Control Troubleshooting
A15 Front End Control Assembly Troubleshooting
Figure 6-8 Connector Detail
The voltage should be ~21.5 VDC steady state at this point. When you switch
from Standard Path to uW Preselector Bypass, you should see a negative going
pulse to 0 VDC on the oscilloscope for ~15 mS before the voltage returns to
~21.5 VDC steady state. The oscilloscope triggering may need to be adjusted
to see the negative going pulse. This can be tested on both connectors that
contain the green wire.
Monitor the yellow or orange wires on each connector, one at a time. The
yellow or orange wire starts at ~21.5 VDC. When switching from uW
Preselector Bypass to Standard Path, you should see a negative going pulse to
0 VDC on the oscilloscope for ~15 mS before the voltage returns to ~21.5 VDC
steady state.
If both the green wires and the yellow or orange wires measure this pulse
correctly, the control logic from the A15, Front End Controller board is
operating correctly.
The black wire is ground.
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 16, “Assembly
Replacement Procedures” for the removal procedure. Press Mode, Spectrum
Analyzer, Mode Preset on the analyzer. Press Input/Output, RF Calibrator, 50
MHz, Freq, 50 MHz, Span, 0 Hz, Amptd, Attenuation, 10 dB, Amptd, More 1
of 2, Internal Preamp Off, System, Alignments, Auto Align, Off. 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 ~-23 dBm on the
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