Keysight NFA Series Noise Figure Analyzers Service Guide 197
RF Section Troubleshooting (N8973B, 74B, 75B Analyzers)
Troubleshooting
• Input Attenuator A
• Input Attenuator B
•Low Band Switch
• YTF Preselector
• RF Front End Assembly
— Input Attenuator A
— Input Attenuator B
—Low Band Switch
— YTF Preselector
If all the power levels and biasing from the A15 Front End Control board
measure correctly up to this point, the most probable cause would be the A13
Front End Assembly.
High Band #2 RF signal path utilizes a high band mixer internal to the A13
RF Front End Assembly for RF input frequencies from 13.6 GHz to
26.5 GHz. Since all the control voltages and biasing were already fully
tested, failures from 13.6 GHz - 26.5 GHz will most likely be caused by the
A13 RF Front End Assembly. If the failure is amplitude related, proper
adjustments such as frequency response and the YTF Preselector adjust
should be performed first before changing the A13 RF Front End Assembly.
Refer to Chapter 12, “Block Diagrams.” for details.
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