234 Chapter4
Troubleshooting the Analyzer
Isolating an RF, LO, IF, or Video Problem
If there is only a horizontal trace with no signal
or noise floor present
1. Check for a peak-detector failure by switching between the
positive-peak detector and sample detector modes.
2. Perform the 2 V reference detector and ground reference detector
diagnostic routines. Refer to “Using the Internal Service-Diagnostic
Routines” in this chapter.
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 analyzer displays a low signal level
A low signal level can cause the CAL AMPTD self-calibration routine to
stop if the REF LVL CAL DAC reaches 255. The routine does not store
the correction factors from an incomplete calibration; however, the
corrections from the incomplete calibration are temporarily retained
and can be viewed by displaying the calibration data (
DISPLAY CAL
DATA) as described in “Using the Internal Service-Diagnostic Routines.”
Refer to Chapter 14 for a description of the displayed error message.
Perform the following steps to help isolate the problem.
1. Check the amplitude of the CAL OUT signal and ensure that the
CAL OUT signal is properly connected to the analyzer input. (The
self-calibration routines perform an initial setup check. If the signal
level is below −40 dBm, the routine fails.)
2. Use
DEFAULT CAL DATA to set the REF LVL CAL DAC to a default
value of 200 by pressing the following analyzer keys.
FREQUENCY, − 2001, Hz
CAL, More 1 of 4, More 2 of 4
DEFAULT CAL DATA
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 analyzer displays a high noise floor
This problem can be due to low gain somewhere along the RF or IF
signal path.
The CAL AMPTD self-calibration routine compensates for the low gain
by increasing the gain of the A9 Third Converter assembly using the
REF LVL CAL DAC. The excessive gain may cause the high noise floor
by amplifying the noise level from the RF section, or over-driving a
stage in the IF section.
To Next Page
Loading...
Need help?
General
