Agilent Technologies 8590 L-Series Especificações descarregar pdf (Página 235)

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Chapter 4 235

Troubleshooting the Analyzer

Isolating an RF, LO, IF, or Video Problem

The analyzer may also fail the displayed average noise performance

veriﬁcation test.

1. Check the REF LVL CAL DAC value using

DISPLAY CAL DATA as

described in “Using the Internal Service-Diagnostic Routines.” This

type of problem causes the DAC value to be close to the 255

maximum.

2. Measure the 321.4 MHz input to the A9 third converter assembly by

connecting the CAL OUT to the INPUT 50Ω with a BNC cable.

75 Ω input only: Connect the CAL OUT to the INPUT 75Ω with the

75 Ω BNC cable.

Then, disconnect the W9 cable assembly from the third converter

and measure at the cable output.

The 321.4 MHz input typically measures between −36 and −39 dBm

with zero input attenuation.

3. Check the signal path from the analyzer input to the output of the

A14 log ampliﬁer assembly. Refer to “IF Power-Level Measurement”

located in Chapter 5 of this service guide.

If the displayed signal amplitude appears too

high

This problem is caused by high gain somewhere along the RF or IF

signal path. The displayed CAL OUT signal appears to have an

amplitude greater than −20 dBm. The excessive gain causes a

calibration error that makes the CAL OUT signal appear higher than

normal.

The

CAL AMPTD self-calibration routine may not fail.

• Check for a REF LVL CAL DAC value of 0 using

DISPLAY CAL DATA

as described in “Using the Internal Service-Diagnostic Routines.”

The values in the ERR column are 0.00 or have a negative value.

• Measure the 321.4 MHz input to the A9 third converter assembly by

connecting the CAL OUT to the INPUT 50Ω with a BNC cable.

75 Ω input only: Connect the CAL OUT to the INPUT 75Ω with the

75 Ω BNC cable.

Then, disconnect the W9 cable assembly from the third converter

and measure at the cable output.

The 321.4 MHz input typically measures between −36 and −39 dBm

with zero input attenuation.

• Check the signal path from the analyzer input to the output of the

A14 log ampliﬁer assembly. Refer to “IF Power-Level Measurement”

located in Chapter 5 of this service guide.

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