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GMA 240 Installation Manual Page 3-3
190-00917-01 Rev. A
3.5 Post Installation Checkout
CAUTION
Check wiring connections for errors before inserting the GMA 240 into
the rack. Incorrect wiring could cause internal component damage.
An in-aircraft checkout may be performed in the aircraft on the ramp with known good microphone,
headset, and avionics receivers.
3.5.1 Lamp Test
1. Apply power to the unit by rotating the pilot intercom knob clockwise.
2. Verify that all annunciators on the front panel are illuminated during initial power up.
3.5.2 Failsafe Operation Check
1. Turn the unit off by rotating the pilot intercom knob fully counter clockwise.
2. Check the failsafe operation by exercising the COM 1 microphone, microphone key, and monitoring
received COM 1 audio over the pilot headphone’s left earpiece.
3. If installed, check that the failsafe warning is heard in the pilot headphone’s left earpiece.
4. Turn the unit back on to continue testing.
3.5.3 Transceiver Operational Check
1. Perform a ramp test radio check by exercising the installed transceivers, microphone, microphone
key, and audio over the headphone.
2. Verify that communications are loud and clear and PTT operation is correct.
3.5.4 Intercom System (ICS) Check
NOTE
Stereo headsets are recommended if stereo jacks are installed.
Alternatively, the installation should employ stereo jacks with a
mono/stereo switch that disconnects the audio panel’s right channel
output from the jack’s ring contact when in mono mode. If a monaural
headset is used in a stereo jack, the audio panel’s right channel output is
shorted to ground by the mono headset’s plug. This causes excess power
supply current to be drawn. While this does not damage the unit’s output
circuitry, prolonged periods (especially at high volume) may cause the
internal power input fuse to open. This is because the unit is optimized
for low-power operation in systems with limited power budgets. In the
case of copilot/passenger positions wired in parallel, any stereo listener
will lose right channel audio when another passenger plugs in a mono
headset.
1. Set the intercom to the ALL mode [Pilot ISO LED off.]