Inconsistent Results; Erroneous Results; Blank Display; Automatic Fault Isolation - HP 8560A Service Manual

Inconsistent Results

Many of the signals measured by the TAM are digitally controlled. If inconsistent results are
obtained, or if failures appear in unrelated areas, the digital control may be at fault. Refer to
the manual troubleshooting procedures for those assemblies to isolate those failures.

Erroneous Results

If the TAM manual probe troubleshooting seems to be giving erroneous results, its
performance can be checked by placing the probe on the TAM test connector (A2Jll) located
on the A2 Controller Assembly and executing the manual probe diagnostics. If either of the
tests fail, the TAM is malfunctioning and should be serviced.

Blank Display

It is possible to use the TAM's Manual Probe Troubleshooting without a display if an HP-IB
printer is available. Refer to Chapter 12 for more information.

Automatic Fault Isolation

Automatic Fault Isolation (AFI) is designed to isolate most faults to one or two assemblies.
AFI can be run with the analyzer's cover in place and requires only the CAL OUTPUT signal
as a stimulus. The entire procedure takes less than 2 minutes to complete if no failures are
found.
AFI performs checks of five functional areas in a pre-defined sequence. The sequence
minimizes the chance of making false assumptions. The TAM checks the analyzer "from the
inside out ." For example, the ADC is checked before the IF is checked. This ensures that if no
signal is detected through the IF, the fault is in the IF Section and not a faulty ADC. (The
ADC measures the video signal from the IF Section.)
The sequence of checks is as follows:

1. Controller Check

2. ADC/Interface Check

3. IF/LOG Check
4. LO Control Check
5. RF Low Band Check

Display/Power Supply

AFI cannot check the Display/Power-Supply Section because this section powers the TAM
and provides the display of AFI results.
Controller Check
The TAM performs a check-sum of all ROMs, RAM
checked, since parts of the CPU could be nonfunctional while the TAM still operates. These
checks are very similar to those done by the analyzer at power-on.
6-12 General Troubleshooting
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