(4)  
This message shows when the inertial system display unit does not receive 28v dc power signal from ADIRUs.

B.  Possible Causes
(1)
ISDU, P5-70

(2)
Wiring problem

(3)
ADIRU, M1749 (left) or M1752 (right)

EFFECTIVITY

34-21 TASKS 807-809
SIL ALL
Page 214 D633A103-SIL Oct 15/2008

C.  Circuit Breakers
(1)  These are the primary circuit breakers related to the fault:
CAPT Electrical System Panel, P18-1
Row Col Number Name
E 5 C01009 ADIRU LEFT DC
E 7 C01007 ADIRU LEFT AC

CAPT Electrical System Panel, P18-2
Row Col Number Name
E 8 C00425 ADIRU LEFT EXC

F/O Electrical System Panel, P6-1
Row Col Number Name
C 14 C01008 ADIRU RIGHT AC
C 15 C00426 ADIRU RIGHT EXC
C 17 C01010 ADIRU RIGHT DC

D.  Related Data
(1)
(SSM 34-21)

(2)
(WDM 34-21)

E.  Initial Evaluation
(1)  Make sure that these circuit breakers are closed:
CAPT Electrical System Panel, P18-1
Row Col Number Name
E 5 C01009 ADIRU LEFT DC
E 7 C01007 ADIRU LEFT AC

CAPT Electrical System Panel, P18-2
Row Col Number Name
E 8 C00425 ADIRU LEFT EXC

F/O Electrical System Panel, P6-1
Row Col Number Name
C 14 C01008 ADIRU RIGHT AC
C 15 C00426 ADIRU RIGHT EXC
C 17 C01010 ADIRU RIGHT DC

(2)  
For
the
applicable
ADIRS,
do
this
task:
ADIRS
BITE
Procedure,
34-21
TASK
801.

(3)  
If the maintenance message does not show on the CDU and the ISDU is powered, then you corrected fault.

(4)  
If the maintenance message shows on the CDU, then do the Fault Isolation Procedure below.

F. Fault Isolation Procedure
(1)  Do this check for 28v dc power signal:
(a)  
Remove the ISDU. To remove it, do this task: Inertial System Display Unit Removal, AMM TASK 34-21-02-000-801.

(b)  
For the left ADIRU:
1) Remove the safety tag and close this circuit breaker:

CAPT Electrical System Panel, P18-2
Row Col Number Name
E 8 C00425 ADIRU LEFT EXC

(c)  
For the right ADIRU:
1) Remove the safety tag and close this circuit breaker:

F/O Electrical System Panel, P6-1
Row Col Number Name
C 15 C00426 ADIRU RIGHT EXC

(d)  
Do a check for a 28v dc from pin 3 to pin 4 (ground) of the connector D2169.

(e)  
Do a check for a 28v dc from pin 3 to pin 4 (ground) of the connector D2183.

(f)  
If there is a 28v dc at pin 3 of connector D2169 and D2183, then do these steps: 1) Install a new ISDU. To install it, do this task: Inertial System Display Unit Installation,

EFFECTIVITY SIL ALL  34-21 TASK 809 
D633A103-SIL BOEING PROPRIETARY -Copyright # Unpublished Work -See title page for details  Page 215 Oct 15/2008 

AMM TASK 34-21-02-400-801. 2) For
the
applicable
ADIRU,
do
this
task:
ADIRS
BITE
Procedure,
34-21
TASK
801.
3) If the maintenance message does not show on the CDU and the ISDU is powered, then
you corrected the fault.
(g)  If there is not a 28v dc at pin 3 of connector D2169 or D2183, then continue.
(2)  Do this check of the wiring between the ADIRUs and the ISDU:
(a)  
Remove the ADIRUs. To remove it, do this task: Air Data Inertial Reference Unit Removal, AMM TASK 34-21-01-000-801.

(b)  
Remove the ISDU. To remove it, do this task: Inertial System Display Unit Removal, AMM TASK 34-21-02-000-801.
　
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