(c)  
Do a continuity check between these pins of connector D3623B for the VOR/marker beacon receiver and connector D2501A for the remote electronics unit:

D3623B  D2501A
pinC4 ------------------pinA15 pinD4 ------------------pinA14

(d)  
If there is not continuity, then do these steps: 1) Repair the wiring. 2) Re-install the remote electronics unit. To install it, do this task: Remote Electronics

Unit (REU) Installation, AMM TASK 23-51-01-000-802. 3) Re-install the VOR/marker beacon receiver. To install it, do this task: VOR/MKR Receiver Installation, AMM TASK 34-51-01-400-801. 4) Do this task: Marker Beacon System -System Test, AMM TASK 34-32-00-730-801. a) If the audio tone is normal, then you corrected the fault for the audio tone, continue for the indications problem.

(e)  
If there is continuity, then do this step and continue:

1)  Re-install the remote electronics unit. To install it, do this task: Remote Electronics Unit (REU) Installation, AMM TASK 23-51-01-000-802.
(4)  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 continuity check between these pins of connector D3623B for the VOR/marker beacon receiver (VOR 1) and the connector for the DEU:

EFFECTIVITY SIL ALL  34-32 TASK 802 
D633A103-SIL BOEING PROPRIETARY -Copyright # Unpublished Work -See title page for details  Page 203 Jun 15/2009 

DEU  VOR 
CONNECTOR  CONNECTOR 
DEU 1  D3973B  D3623B 
pin C3  ------------------ pin B13 
pin D3  ------------------ pin C13 
DEU 2  D3975B  D3623B 
pin C3  ------------------ pin B13 
pin D3  ------------------ pin C13 
(d)  If there is not continuity, th en 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 for the indications problem.
(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.
(5)  Do this check of the display electronics unit (DEU) if there are still indications problem:
(a)  
For
the
applicable
DEU,
do
this
task:
DEU
Self-Test
Procedure,
31-62
TASK
802.

(b)  
If the DEU shows FAILED, then do these steps:

1) Replace the DEU, M1808 (No. 1) or M1809 (No. 2).
These are the tasks:
Display Electronic Unit Removal, AMM TASK 31-62-21-000-801,
Display Electronic Unit Installation, AMM TASK 31-62-21-400-801.
2)  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.
(6) Replace the remote electronics unit, M1353 if there are still audio tone problems. These are the tasks: Remote Electronics Unit (REU) Removal, AMM TASK 23-51-01-000-801, Remote Electronics Unit (REU) Installation, AMM TASK 23-51-01-000-802.
　
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