Garmin APOLLO GX SERIES, Service Manual

Page: 125 / 166

Garmin AT Rev --
© 2004 Garmin AT GX Service Manual 9-3
Symptoms
SYMPTOM CAUSE ACTION
Hold or flip/flop input
failure 1. External switch
2. Nav board
1. Check continuity of external switch.
2. Replace the NAV board. (See NAV
Board Replacement procedure.)
Squelch open or close
failure Factory alignment not to
current specification Replace Comm board. (See Comm
Board Replacement procedure.)
Can’t access data card
Data card failed
1. Data card
2. NAV board
1. Reinsert data card (make sure it is
right side up).
2. Try another data card.
3. Replace the NAV board. (See NAV
Board Replacement procedure.)
Loss of communication
with peripheral device 1. Serial port
configuration
2. Serial port
communication
3. NAV board
1. In the Test mode, check that the
serial port setup is correct.
2. Check the Serial port. (See Serial
Ports on page 7-13).
3. Replace the NAV board. (See NAV
Board Replacement procedure.)
Comm is interfering w/
GPS
(Some of the action steps
are assuming that there
are separate GPS and
Radio units.)
1. Harmonics from
Comm
2. Proximity of antennas
3. Aircraft component
interference
1. Install notch filter part # 162-1059
on GPS antenna coax connector on
the back of the chassis.
2. Try new RG-142 instead of RG-58
coax for Comm and GPS antennas.
3. Ground Nav/Comm and GPS racks
together and to A/C ground.
4. Rearrange the stack to get
maximum distance between the
GPS and Nav/Comm.
5. Separate the GPS and Nav/Comm
wiring at the back of the rack. Wrap
shielding around each bundle of
wires, then ground these to A/C
ground.
6. Minimize any extra wire lengths.
7. Try grounding wire shields at both
ends of the wire.
8. Separate Comm and GPS
antennas.
9. Isolate to interfering component.
10. Move GPS antenna from line of
sight with interfering equipment.
Comm not changing
frequencies 1. Channels locked
2. Comm board
1. Replace Comm board. (See Comm
Board Replacement procedure.)