Methods Of Fault Isolation; Fault Isolation Aids; Bit; General - Honeywell XK516D1 Maintenance Manual

9. Fault Isolation
A. General
This section contains information and instructions for fault isolation of the HF Transceiver.
The information is intended to aid in isolating and eliminating faults to the Module level.
B. Methods of Fault Isolation
Faults are generally recorded during operation by the Transceiver's continuous monitoring
system (BITE). Faults that occur during operation are stored according to ARINC 604 in the
internal fault memory with date, flight phase, and additional fault data. These fault reports can
be analyzed on the test bench, and used to assist in fault isolation.
The fault detection scope of the BITE encompasses faulty modules, and in some cases, faulty
functional assemblies on these modules. For the purposes of further fault analysis, an inter-
nal self-test can be triggered on the test bench. This self-test is also automatically executed
at power up and after every power interrupt greater than 5 seconds. The results of the
self-test may be used to determine whether any faults are still present, or to identify faults not
previously stored in memory.
(1) Unidentified faults
(a) In the event of a no-fault indication, or problem reports for which no additional fault
trouble-shooting data is provided, or where a malfunction is suspected, which has
not been recorded by the internal BITE, the Return-to-Service Test Procedure must
be performed. The Acceptance Test Procedure (ATP) involves checking the Trans-
ceiver functions by measuring the specified data. If no fault occurs during the test
procedure, the cause of the malfunction may be in the aircraft cabling or other con-
nected equipment.
(b) If the internal BITE function cannot be run, or cannot be displayed as a result of a
fault; i.e., a processor fault or a power supply fault, the basic voltage test procedure
must be executed (Refer to paragraph F). This voltage test checks all Transceiver
voltages and refers to Controller or Power Supply fault isolation procedures.
(2) Specified faults
(a) If the fault is known (FAULT indicator is ON), and the equipment is still found to be
defective, there may be no need to carry out a full ATP. Fault Isolation can begin at
the indicated level.
(b) Fault isolation involves locating the fault at module level on the basis of the results
of the BITE evaluation and execution of additional tests.
C. Fault Isolation Aids

(1) BIT

The built-in test (BIT) generally detects malfunctions and records these in the Transceiv-
er fault memory. The fault memory must be read out in order to obtain a fault report.
(2) Schematic Diagrams
A complete set of schematic diagrams covering the Transceiver and it's modules and
subassemblies is provided at the rear of this section.
I.B.1516A
Honeywell
COMPONENT MAINTENANCE MANUAL
PART NUMBER 964-0452
23-12-01
Page 115
Oct 25/02