This section contains
troubleshooting procedures for unit (second
echelon) maintenance level
personnel. The possible causes assume that
all operating controls are
properly set and that the LDF is properly
installed and connected for
a. External Problem Isolation.
When problem symptoms are noted
while the LDF is connected to an external data link, the LDF should be
connected by an equivalent link to the local backup LDF. The operations
should then be duplicated to see if the problem symptoms still exist.
This procedure eliminates the possibility of problems being the result of
data link or remote LDF troubles.
b. Parallel Problem Isolation. The symptoms listed assume that all
other functions are operating properly unless specifically noted
otherwise. When a transmit operation is specified, the receiving LDF is
is specified, the transmitting LDF is assumed to be operating properly.
c. Mode B Power-On Diagnostic Built-In Test.
At power-up during
Mode B operations, the software checks out the system through the
following tests: lamp test, programmable read-only memory (PROM)
checksum, random access memory (RAM) test, central processing unit (CPU)
test, short loop, and sync comparison test. During this diagnostic test,
the ERROR LED flashes at a 1-hertz rate. RCV, SEND, and LOAD LEDs are
used to indicate which test is being executed (Table 1.) If all tests are
run successfully, no LEDs are lit at the end of the diagnostic test. If
an error is found in one of the tests, the ERROR LED is lit continuously
along with the others to indicate which test is failing. The operator
may switch the LDF from Mode B to Mode A if the diagnostic test fails.
The LEDs go off but will come back on when the LDF is returned to Mode B.
Troubleshooting chart, Table 2, should be used if unit maintenance
personnel are available to perform the troubleshooting procedures. If
direct support maintenance level personnel are available, use the
troubleshooting charts provided in Chapter 4 of TM 11-5815-615-23. The
information provided in Table 2 is also included in the tables in Chapter
4; therefore, there is no need to reference this table when
troubleshooting at the direct support level.
When corrective action
requires operating the LDF, refer to TM 11-5815-615-10/TM 09955A-10/1.