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Page 4-56
GNS 400W Series Maintenance Manual
Rev. A
190-00356-05
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In the absence of 90 modulation.
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In the absence of both 90 and 150 Hz modulation.
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In the absence of RF.
The G/S +FLAG output must be 0 ± 25 millivolts (Flagged) when measured at the G/S +FLAG
J6-30 and G/S -FLAG (G/S COMMON) J6-31 outputs with a standard glideslope deviation test
signal at 334.7 mHz (108.10 mHz LOC freq) when the RF level is lowered to the flag threshold
level such that it causes the course deviation output (G/S +UP) J6-32 to be less than 50% of
standard deflection. 50% of standard deflection is 39 millivolts. Flag threshold deflection
percentage must be greater than 50%.
Spurious Response
The RF level of an undesired image frequency test signal of 245 mHz must be greater than -27
dBm to produce an AGC level equal to that of a desired frequency having a level of -87 dBm
when the glideslope receiver is tuned to 335 mHz. The undesired test signal must consist of a
standard glideslope signal in which the 150 Hz signal is modulated at 30%.
4.8 TESTING
FAILURES
Table 4-6 lists recommended actions based on main board failures that may occur during testing.
Perform the recommended actions in the order given in the table. For all other boards, replace the
board if any failure occurs during testing.
Table 4-6. Testing Failures
⎯
Main Board
TEST FAILURE
RECOMMENDED ACTION
BUS Power
Return the unit for service
Push Button Response
Check Applicable Flex
Replace Keyboard
Replace CDU
Return the unit for service
Rotary Knobs
Check Applicable Flex
Replace CDU
Return the unit for service
Data Card Tests
Return the unit for service
Photocell
Check Applicable Flex
Replaced Keyboard
Replace CDU
Return the unit for service
Lighting BUS Input
Return the unit for service
Lighting BUS AC
Return the unit for service
Lighting BUS DC
Return the unit for service
Memory Battery Voltage
Replace Memory Battery
Display Pattern Test
Check Applicable Flex
Replace CDU
Return the unit for service
Display Max Level Test
Replace Inverter Board