Keysight N8973B User Manual

Keysight NFA Series Noise Figure Analyzers Service Guide 239
Front End Control Troubleshooting
A15 Front End Control Assembly Troubleshooting
Power Supply Verification
Looking at the test board, verify power supply green LED's DS5, DS6, DS7 and
DS8 located under the J2 connector are turned on. Additionally red LED's DS9
and DS10 should also be on. The power supply voltages are listed in the table
below.
If any of the power supply LED's are not turned on, see Chapter 2, “Boot Up
and Initialization Troubleshooting”.
Input Attenuator A Control Logic Verification (N8973B, 74B, 75B)
Press MODE/MEAS, Spectrum Analyzer, OK, AMPTD, Attenuation, Mech
Atten, 0 dB on the analyzer.
Attenuation LED's DS15-20 on the test board should be off.
When the input attenuation is changed from 0 dB to 2 dB, the 2 dB Step LED
DS15 should illuminate. When the input attenuation is changed from 2 dB to
4 dB, DS15 and DS16 should be illuminated as per Table 6-4.
If this is incorrect, the most probable cause is the A15, Front End Control
assembly.
The analyzer default setting for RF Coupling is AC mode. Verify the AC Select
LED DS14 is illuminated at this time. Press Input/Output, Select Input, RF, RF
Coupling, DC On on the analyzer. DS14 should turn off and DS11, DC Select
LED should illuminate. Switch the RF Coupling back to AC. If the LED's do not
illuminate correctly, the most probable cause is the A15 Front End Control
Assembly.
Table 6-3 Power Supply Voltages
LED Power Supply
DS5 +15 VDC
DS6 +9.0 VDC
DS7 +5.2 VDC
DS8 -15 VDC
DS9 +25 VDC
DS10 +25 VDC
Table 6-4 Input Attenuator A LED’s
Attenuator Setting (dB) DS15 DS16
0OFFOFF
2ONOFF
4ONON

Keysight N8973B Specifications

General

Brand	Keysight
Model	N8973B
Category	Measuring Instruments
Language	English