Symmetricom 5071A, Assembly And Service Manual

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2. Service
Top-Level Diagnostic Tree (Diagnostic Section 1)
44
1.0.9 Delayed Failures, Warnings, and
Messages
The error messages covered in sections 1.1.1, 1.2.1, 1.3.1, and 1.4.1
describe the error conditions which can occur respectively at power-up,
during self-test, during servo lock-up, and immediately following servo lock-
up. Error conditions can occur later than this, for example due to component
failure, aging, or progressive loss of CBT performance. These will be
described as delayed error conditions.
Delayed error conditions include “Fatal Errors” which result in the instrument
going off-line, “Warnings” of unsatisfactory internal conditions which do not
necessarily cause operation to fail completely, and “Messages” which are
advisory.
Use the following information to investigate possible malfunctions. Examine
the instrument's log and record any error conditions which have occurred
before beginning troubleshooting.
1.0.9.1 Delayed Fatal Errors
Operational fatal errors are usually caused by a significant malfunction of one
of the instrument's functional blocks. These errors will usually prevent
subsequent operation and can be diagnosed in the usual way using the top
level diagnostic procedure.
1.0.9.2 Delayed Warnings
Warnings which occur in normal operation may not always require the
instrument to be removed from service, especially when some loss of
performance is tolerable. For example declining CBT performance will result
in a “
CBT signal low
” warning. This warning is only issued once, as it
does not cause the instrument to stop operating.
Some errors may occur due to transient conditions, or perhaps be caused by
unusually strong external EMI (Electro-Magnetic Interference). Such error
conditions can be cleared using the front-panel
Shift , 5 , Enter sequence.
When ever possible, however, the instrument should be run through
Operational Verification procedure as a precaution. The procedure in section
1.4.1 can be used to investigate the cause of warnings.
1.0.9.3 Delayed Advisory Messages
Advisory messages have several degrees of importance, and may occur
together with fatal errors. Messages are discussed in section 1.7.1.