Symmetricom 5071A, Assembly And Service Manual

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2. Service
Top-Level Diagnostic Tree (Diagnostic Section 1)
63
1.6.1 5071A Profiling Results Evaluation
A 5071A Profiling report example appears on the next page. You can use the
example along with the explanations below to interpret your instrument’s
profiling results.
VCXO Control Value
The present A19 VCXO adjustment state is shown by the
VCXO Control
value
. This value normally changes with time as a result of aging in A19.
There is no resulting loss of performance.
If the value is outside the -90% to +90% range, then the A19 VCXO Set-Point
Adjustment (3.9.1.7 and 3.9.1.8) should be performed as soon as is
convenient.
The instrument will experience a Fatal Error if the value reaches
±
100%.
Depth of Modulation
The
Depth of Modulation
can help isolate faults to either the CBT or the
instrument electronics.
A “
Band 3
” modulation depth combined with a peak-output current below
100 nA indicates deteriorating CBT performance.Be sure to thoroughly
diagnose the entire instrument before considering the A17 CBT to be at fault.
Contact Symmetricom for further assistance.
Signal to Noise Ratio
The
Signal to Noise Ratio
is an estimate of the current overall operating
condition of both the CBT and instrument electronics.
•
If the result is
Band 1
, the instrument’s stability should meet
specification. CBT problem is unlikely.
•
If the result is
Band 2
, the test is indeterminate. High probability that CBT
is performing to specifications.
•
If the result is
Band 3
, instrument stability will probably not meet
specification. CBT problem is likely. Consult Chapter 1 on Performance
Tests to confirm poor performance.
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