Troubleshooting; Troubleshooting Equipment Required; Self-Test Failures - Garmin GNC 250 Maintenance And Repair Manual

2.1

TROUBLESHOOTING EQUIPMENT REQUIRED

· 0-30 Volt DC / 6-Amp Power Supply
· Digital Multimeter
· 20 MHz Oscilloscope
· Adjust Power Supply to 14 Volts
2.2

SELF-TEST FAILURES

The GNC 250/300 monitors many of its internal functions and displays a message to alert the user
should a failure occur. The table below shows the recommended repair for each self-test failure
message.
Altitude input fail
Course input fail
(300 only)
Data card failed
Data card write fail
Fuel/Air input fail
Memory battery low
No altitude input
(300 only)
Osc needs adjustment
RAM failed
Receiver failed
Stored data lost
Configuration reset
EEPROM write fail

TROUBLESHOOTING

MESSAGE
Verify connections to altitude serializer/encoder
Verify connection between CPU Board and Comm
Receiver Board
Replace comm chassis sub-assembly
Replace CPU Board
Check ARINC 429/RS422 course input connections
Replace CPU Board
Replace NavData® card
Replace Interface Board (see Section 3.2.3)
Replace user data card
Replace Interface Board (see Section 3.2.3)
Check connections to fuel/air data system
Replace CPU Board (see Section 3.2.4)
Replace memory battery (see Section 4.1)
Verify connections to altitude serializer/encoder
Verify connections between CPU Board and Comm
Receiver Board
Replace Com/Chassis sub-assembly (see Section 3.2.2)
Replace CPU Board (see Section 3.2.4)
Replace GPS Receiver Board (see Section 3.2.5)
Replace CPU Board (see Section 3.2.4)
Replace CPU Board (see Section 3.2.4)
Replace CPU Board (see Section 3.2.4)
Replace GPS Receiver Board (see Section 3.2.5)
Replace memory battery (see Section 4.1)
Replace CPU Board (see Section 3.2.4)
Replace CPU Board (see Section 3.2.4)
SECTION 2
RECOMMENDED REPAIR*
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