9
SECTION 2
TROUBLESHOOTING
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.
MESSAGE
RECOMMENDED REPAIR*
Altitude input fail
Verify connections to altitude serializer/encoder
Verify connection between CPU Board and Comm
Receiver Board
Replace comm chassis sub-assembly
Replace CPU Board
Course input fail
(300 only)
Check ARINC 429/RS422 course input connections
Replace CPU Board
Data card failed
Replace NavData® card
Replace Interface Board (see Section 3.2.3)
Data card write fail
Replace user data card
Replace Interface Board (see Section 3.2.3)
Fuel/Air input fail
Check connections to fuel/air data system
Replace CPU Board (see Section 3.2.4)
Memory battery low
Replace memory battery (see Section 4.1)
No altitude input
(300 only)
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)
Osc needs adjustment
Replace GPS Receiver Board (see Section 3.2.5)
Replace CPU Board (see Section 3.2.4)
RAM failed
Replace CPU Board (see Section 3.2.4)
Receiver failed
Replace CPU Board (see Section 3.2.4)
Replace GPS Receiver Board (see Section 3.2.5)
Stored data lost
Replace memory battery (see Section 4.1)
Configuration reset
Replace CPU Board (see Section 3.2.4)
EEPROM write fail
Replace CPU Board (see Section 3.2.4)
