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5.6
BOARD LEVEL FAULT ISOLATION
Figure 5-2 shows signal flow between individual circuit cards, and the jacks and/or test
points for measuring signal values. This information, along with the BITE check detailed in Para-
graph 5.4.2 and the Performance Tests detailed in Paragraph 5.5 should be used in isolating mal-
functions to the board level. Receiver settings, signal generator settings, and connector pin location
diagrams are
~hown
as part of Figure 5-2. The following procedures should be used to perform signal
level tests:
1. Set signal generator outputs as specified in Figure 5-2.
2. Set receiver front panel controls as specified in Figure 5-2.
3. Measure values indicated at each jack or test point using appropriate test equipment.
4. Tolerances are:
:!:3
dBm;
:!:O.S
volts.
Once a fault has been isolated, the faulty circuit card should be replaced in accordance with
the Receiver Assembly and Disassembly procedures detailed in Paragraph 5.7; and receiver proper
operation verified. Verification is accomplished by performing BITE check (Paragraph 5.4.2) and Per-
formanceTests (Paragraph 5.5).
5.7
RECEIVER ASSEMBLY AND DISASSEMBLY PROCEDURES
The following paragraphs outline the procedures for removal and installation of the individual
circuit card assemblies used in the RA6790/GM HF Receiver. A complete list of these assemblies
is
contained in SECTION VI, Replacement Parts List, of this instruction manual.
5.7.1
Preliminary Procedure
Prior to removing or installing any assembly it is necessary to disconnect the Receiver from
its power source. It is also necessary to remove the Receiver from the system (except to replace the
fus!:').
NOTE
Ensure that all system cables are disconnected from the Receiver prior .to re-
moving the Receiver from its mounts. Place the Receiver on a suitable work
space large enough to allow for positioning the Receiver either horizontally or
vertically as required for removal of the desired board. The only tools required
for LRU removal or installation are a flat-blade screwdriver and a screw starter.
Adequate light should be available for ease in reading internal cable, jack, and
connector numbers, and for aligning LRU mounting holes with corresponding
mounting fixtures on the receiver chassis.
CAUTION
Do not expose the Receiver to direct ultraviolet light while per-
forming the following steps. Such exposure may cause erasure
of data stored in the EPROMS.
5.7.2
Top and Bottom Covers
If boards A2, A3, A 7, or A8 are to be removed or installed, only the receiver's bottom cover
must be removed for access. If boards A4, AS, A6A 1, A6A2 or AIO are to be removed or installed,
5-16
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