Chapter 9 435
IF Section
Troubleshooting Using the Diagnostic Software
Troubleshooting A5 Using Diagnostic Software
The IF diagnostics in the software include:
DC probe (using the TAM)
Gain checks
LC frequency checks
Xtal frequency checks
DC Probe
Using the up/down arrow, select "DC probe" in the IF diagnostics menu.
Connect the TAM (Test and Adjustment Module) and use the dc probe
as directed by the diagnostic software program. The current into each
IF filter or amplifier stage is measured and compared to limits. This
helps locate shorted or open components. An asterisk will appear at the
points of failure. An @ indicates a measurement error (bad setup, GPIB
not responding, test equipment error, or major failure).
NOTE In the following gain and frequency checks, an 8566B or 8563E is the
preferred spectrum analyzer.
Gain Checks
Using the up/down arrow, select "Gain checks" in the IF diagnostics
menu. An 3335A synthesizer/level generator is used as a stimulus and
a spectrum analyzer is used to measure the response. The gain of each
stage is measured and compared to limits. An asterisk will appear at
the points of failure. An "@" indicates a measurement error (bad setup,
GPIB not responding, test equipment error, or major failure).
LC Frequency Checks
Using the up/down arrow, select "LC frequency checks" in the IF
diagnostics menu. An 3335A synthesizer/level generator is used as a
stimulus and a spectrum analyzer is used to measure the response. The
center frequency tuning range and the bandwidth adjustment range
are measured for each pole. The LC pole selection menu allows selection
using the up/down arrows. Select "All Poles" first, unless a particular
pole is suspected to have failed. An asterisk will appear at the points of
failure. An "@" indicates a measurement error (bad setup, GPIB not
responding, test equipment error, or major failure).
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