803. Audio Tone Normal, Indication Problem -Fault Isolation
A. Description
(1) Indication does not show on the display when passing a marker, however audio tone is normal.
B. Possible Causes
(1)
VOR/marker beacon receiver, M1724.
(2)
Display electronics unit (DEU), M1808 (No. 1) or M1809 (No. 2).
(3)
Wiring.
C. Circuit Breakers
(1) This is the primary circuit breaker related to the fault:
CAPT Electrical System Panel, P18-1 Row Col Number Name A 1 C01374 RADIO NAVIGATION VOR/MKR BCN 1
D. Related Data
(1)
(SSM 34-32-11).
(2)
(WDM 34-32-11).
E. Initial Evaluation
(1) Do this task: Marker Beacon System -System Test, AMM TASK 34-32-00-730-801.
(a)
If the indication do not show on the display, then do the Fault Isolation Procedure below.
(b)
If the indications are normal, then there was an intermittent fault.
F. Fault Isolation Procedure
(1)
Do
this
task:
VOR/Marker
Beacon
Receiver
BITE
Procedure,
34-51
TASK
801.
(a)
If the VOR/marker beacon BITE test shows a fault, then go to the fault isolation task for the applicable maintenance message to correct the fault. 1) Do this task: Marker Beacon System -System Test, AMM TASK 34-32-00-730-801.
a) If the indication does not show on the display, then continue. b) If the indication is normal, then you corrected the fault.
(b)
If the VOR/marker beacon BITE test does not show a fault, then continue.
(2)
Do this check of the wiring between the DEU and the VOR/marker beacon receiver:
(a)
Remove the applicable DEU, M1808 (No. 1) or M1809 (No. 2). To remove it, do this task: Display Electronic Unit Removal, AMM TASK 31-62-21-000-801.
(b)
Remove the VOR/marker beacon receiver, M1724. To remove it, do this task: VOR/MKR Receiver Removal, AMM TASK 34-51-01-000-801.
(c)
Do a check for an open circuit between these pins of connector D3623B for the VOR/marker beacon receiver (VOR 1) and the connector for the DEU:
DEU VOR CONNECTOR CONNECTOR DEU 1 D3973B D3623B
pinC3 ------------------pinB13 pinD3 ------------------pinC13
EFFECTIVITY SIL ALL 34-32 TASK 803
D633A103-SIL BOEING PROPRIETARY -Copyright # Unpublished Work -See title page for details Page 205 Feb 15/2009
DEU 2 D3975B D3623B
pinC3 ------------------pinB13 pinD3 ------------------pinC13
(d)
If there is not continuity, then do these steps: 1) Repair the wiring. 2) Re-install the VOR/marker beacon receiver. To install it, do this task: VOR/MKR
Receiver Installation, AMM TASK 34-51-01-400-801. 3) Re-install the DEU. To install it, do this task: Display Electronic Unit Installation, AMM TASK 31-62-21-400-801. 4) Do this task: Marker Beacon System -System Test, AMM TASK 34-32-00-730-801. a) If the indications are normal, then you corrected the fault.
(e)
If there is continuity, then do these steps and continue:
1) Re-install the VOR/marker beacon receiver. To install it, do this task: VOR/MKR Receiver Installation, AMM TASK 34-51-01-400-801.
2) Re-install the DEU. To install it, do this task: Display Electronic Unit Installation, AMM TASK 31-62-21-400-801.
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