238 Chapter4
Troubleshooting the Analyzer
Using the Internal Service-Diagnostic Routines
Using the Internal Service-Diagnostic
Routines
The 8590 E-Series and L-Series spectrum analyzers, 8591C cable TV
analyzers, and 8594Q QAM analyzers have an internal
service-diagnostics routine menu available within the calibration
menus.
Reference voltages and ramps are routed through a MUX located on the
A7 analog interface board assembly. These voltages and ramps can be
displayed on the analyzer or on an oscilloscope by connecting a probe to
A7TP2 when a service-diagnostic routine is performed. The only
exception is the 2VREF and GNDREF, these reference voltages
originate on the A16 processor/video board assembly.
The service-diagnostic routines included in this section are the most
useful routines used to help isolate problems with the A7 analog
interface and A16 processor/video board assemblies. Illustrations are
included with each procedure to show the expected displayed results.
Access the service-diagnostic routine softkeys by pressing the following
analyzer keys.
CAL, More 1 of 4, More 2 of 4
SERV DIAG
Note that whenever an analyzer setting has been changed while in a
service-diagnostic routine, you must return to the service-diagnostic
routine softkey menu by pressing the key sequence listed above.
If a flat line appears at midscreen
When a service-diagnostic routine is selected and only a flat line
appears at midscreen, connect an oscilloscope to A7TP2. If the expected
signal is there, then the ANA_TEST line is either shorted or open. This
can be caused by bent pins or solder bridges on either the A7, A16, or
A15 board assemblies. This condition will cause the frequency
calibration routine to fail, as it uses this line to set up the sweep ramp
at the beginning of the calibration routine.
If a service-diagnostic routine fails
When a service-diagnostic routine fails, it is recommended to continue
verifying the rest of the service-diagnostic routines to isolate a failure
for further troubleshooting. For example, the main coil driver is
dependent on the sweep ramp and the −10 V reference to function
properly.
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