SECTION
1
DESCRIPTION AND OPERATION
1.1
INTRODUCTION
This manual provides functional testing and assembly-levelrepair information for the GARMIN GMA 340,
GMA 340H and GMA 340 Dual ADF Audio Panels. Reference to GMA 340 throughout this manual refers to all
versions of the unit. Information pertaining to the installation and operating instructions can be found in the
GMA 340 Audio Panel Installation Manual, 190-00149-0
1.
This manual is designed to aid the bench technician
in isolating failures
co
the assembly level only. If necessary, the GMA 340 can be returned to GARMIN for all
service work, including maintenance and repair. Contact GARMIN at the following address for more details:
GARMIN
1200
E.
151st
Street
Olathe,
KS
66062
1-913-397-8200 or 1-800-800-1020
1.2
GENERALDESCRIPTION
The GARMIN GMA 340
is
a
panel mounted TSO’d audio panel that provides control of the aircraft audio
system. The GMA 340 provides flexibility in switching up to three microphone and audio transceiver
communication inputs. Audio selection ofNAV 1,NAV 2, ADF, DME and marker audio is available on the
GMA 340 and GMA 340H. In addition, selection of ADF 1and ADF 2 is provided on the GMA 340 Dual ADF.
The GMA 340 includes a voice activated (VOX) intercom system and a three-lamp marker beacon receiver and
display. One or two stereo entertainment inputs are also provided. (One on the GMA 340 Dual ADF, two on the
other units.)
The VOX intercom uses rotary knobs for volume and squelch adjustment while selection of
all
other functions is
accomplished with the use of pushbuttons.
Marker HI and LO and button annunciation is accomplished with LED devices. Front panel backlightingof
button function, squelch and volume control knobs is provided by LED’Scontrolled by the aircraft lightingbus.
On the GMA 340 and GMA 340H the split com function allows the pilot and copilot to talk on Com
1
and Com
2
simultaneously.
The unit is constructed from high quality materials and uses surfacemount components extensively. Specialized
equipment and procedures are required to repair circuit boards having surface-mounted components. GARMIN
does not authorize the repair of GMA 340 circuit boards. If necessary, circuit boards and assemblies for the
GMA 340 can be economically replaced through the GARMIN board exchange program.
The following assemblies and printed circuit boards can be field replaced:
0
Front Panel Assembly-Contains the front panel bezel, button key cap assembly, marker beacon lamp
assembly and front panel board assembly.
0
Marker Beacon Lamp Rack Assembly-Contains marker beacon incandescent lamps and lamp rack.
Fits onto the front panel assembly.
0
Flexible Circuit Cables-Connects the frontpanel to the main circuit board assembly.
190-00149-02
Rev
B
1-1
The document reference is online, please check the correspondence between the online documentation and the printed version.
