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190-01007-A1 System Maintenance Manual GTN 6XX/7XX Part 23 AML STC
Rev. 7 Page 5-2
The GTN COM does
not transmit.
The PTT input is not being pulled
low.
Check that the MIC 1 Transmit (P1003-
11) input is pulled low for transmit. The
state of this discrete input can be
monitored on the Discrete Inputs page
found on the GTN Diagnostics page.
See Section 3.4.5.
No transmit power to COM.
Make sure power input is connected to
the COM 44-pin connector P1003-30,
-43 and -44 and ground to P1003-37,
-38, and -40.
The input voltage is too low.
Increase input supply voltage to
>11VDC.
The side tone level is
too low or too high.
Wrong type of headsets or side
tone level needs adjustment.
If necessary, adjust the side tone level.
Side tone adjustment is found on the
COM Setup Config Mode page.
OBS Resolver won’t
calibrate.
Incompatible resolver or improper
connection.
Check the resolver specifications and
wiring.
OBS indication on
GTN does not agree
with OBS setting.
GTN resolver input not calibrated
correctly.
Check wiring and calibration.
Resolver has not been calibrated.
GTN TAWS Audio
not heard.
TAWS audio volume level set too
low.
Increase TAWS audio volume level.
Check wiring.
Check audio panel volume and
audio wiring.
Main software version has just
been updated.
Allow up to 5 minutes for the TAWS
audio clips to load. Cycle power on the
GTN and verify that TAWS audio is
working properly.
GTN is not receiving
heading from
compass system
(ARINC 429 heading
input used).
ARINC 429 input port speed not
correct.
Check ARINC 429 input port speed
setting for port that device is connected
to and verify that the speed is correct for
that device.
Wiring connections are incorrect.
The raw data being received by the GTN
can be monitored on the ARINC Inputs
page found on the GTN Diagnostics
page. See Section 3.4.5.
Check wiring.
Problem Possible Cause Corrective Action