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3. Verify reception of the signal by connecting a suitable speaker or headphones. If the
station is not heard (confirm that the station is on the air), observe the RF level
meter on the Mode LCD. If the signal strength meter (RF level) has no level indi-
cation, the Al Low Pass Filter Module is defective and should be replaced.
5.4.4
A4
~n
IF/AF (AF
Section) Check
If the RF level meter indicates a signal is present as specified in Paragraph 5.4.3, adjust the
front panel MAIN LINE LEVEL potentiometer (screwdriver - set) to determine if the signal can be ..
observed a t Line lout
(13-).
If the signal cannot be found the A4 Main IF/ AF board
(AF
portion)
is faulty and the A4 must be replaced.
.
5.4.5
AS ISB
(AF
Section) Check (if installed)
Tune to a known
lo~al
AM station. Depress the ISB pushbutton and listen for the presence
of the signal. 'If the signal cannot be heard, adjust the ISB LINE LEVEL potentiometer (screwdriver
adjust) on the front panel to determine if the signal can be heard or observed at Line 1 or Line 2
out
(13).
If not found, the AS ISB (AF portion) is faulty and ASmust be replaced.
5.4.6
A6Al Remote Serial Asynchronous Interface Check(if installed)
Receiver.
1. Ensure that all previous paragraphs have been successfully accomplished.
2. Connect a suitably wired remote terminal to the Receiver via connector A6Al W111
on the rear panel.
3. Enter $99GCR on the terminal keyboard and observe the results on the remote
display. If data
is
displayed, A6Al is functional. If data is not displayed, A6AI
is faulty and must be replaced.
NOTE
99 represents the receiver number. If the receiver number
is different, enter the desired number instead of 99.
This completes the Operational Checkout and Fault Isolation Procedures for the
RA6790/GM
5.5
RA6790/GM PERFORMANCE TESTS
RA6790/GM performance tests can be most effectively carried out if the technician gains
some degree of familiarization with the operating instructions and circuit descriptions'provided in
Sections III and IV, respectively. Parts lists and component location
diagrarr,~s
are located in Section VI,
These performance test procedures may be used for initial inspection, periodic checks and
to confirm performance specifications after repairs have been made. These tests determine Synthe-
sizer performance, Audio Power and Distortion, Gain Modes, and Final IF Frequency. The. tests
should be conducted only by skilled technicians using the equipment listed in Table 5-2.
All tests should be conducted using Figure 5-1 as a standard test set-up. Equipment should
be allowed a warm-up period of at least 30 minutes prior to conducting the test. If the Receiver
does not satisfactorily pass a test, refer to Paragraph 5.6, Board Level FatiIt Isolation.
5-10
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