S 394-082
 (2)  Apply a bead of BMS 5-95 sealant to the faying surfaces of the DME antenna as shown in Fig. 401 (AMM 51-31-01/201).
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747-400
MAINTENANCE MANUAL

 NOTE:____Make sure that no air gets caught under the sealant. Fill more than the necessary level so you can make the surface smooth and level.
 (a)  
Make a smooth 45-degree bead with the spatula.

 (b)  
Remove the unwanted sealant.

 (c)  
Let the sealant dry.

 (d)  
Apply a pressure seal around the electrical connector.

 S 864-025
 (3) Remove the DO-NOT-CLOSE tags and close these circuit breakers:
 (a)  P7 Overhead circuit Breaker Panel
 1) 7B8 NAV RADIO DME L
 2) 7B19 NAV RADIO DME R

 J. Put the Airplane Back to Its Usual Condition
 S 864-020
 (1)  Remove electrical power if it is not necessary (AMM 24-22-00/201).
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747-400 MAINTENANCE MANUAL
 AUTOMATIC DIRECTION FINDER SYSTEM - DESCRIPTION AND OPERATION
_____________________________________________________________
 1.  General (Fig. 1 and 2)_______
 A.  The Automatic Direction Finder (ADF) system is a navigational aid which receives radio signals from 190 to 1750 kHz and provides bearing to selected stations relative to the airplane centerline. Signal sources used are standard AM broadcast and low frequency nondirectional beacons.
 B.  Two ADF systems are installed in the airplane (Left ADF and right ADF). Each system consists of one receiver and one combined sense/loop antenna. The ADF frequency and mode selections are done manually from the Control Display Unit (CDU) through the FMC (Ref 34-61-00) or directly from the CDU if both FMCs fail.
 C.  The ADF system receives an electromagnetic wave transmitted by a ground station. The loop antenna intercepts the magnetic portion of the wave and couples this signal to the ADF receiver. The sense antenna intercepts the electric portion and couples this signal to the receiver. The bearing information and fault status from each ADF receiver are sent on an ARINC 429 bus to the Radio Magnetic Indicator (RMI) (Ref 34-22-00) and to the left, right, and center EFIS/EICAS Interface Units (EIUs) (Ref 31-61-00).
 D.  The EIUs multiplex this information with input from other airplane systems and provide a single output to the captain's and first officer's Navigation Display (ND), which displays ADF bearing output.
 E.  The ADF system also receives identification codes from nondirectional beacons and radio signals from a standard AM broadcast station. The receiver processes these signals and sends the audio output to the Audio Management Unit (AMU) of the flight interphone system (Ref 23-51-00).
 F.  From the AMU, the audio output can be heard over the cockpit speakers and pilot's headsets. The mode selection and volume control of the audio signals can be adjusted from the Audio Control Panels (ACPs).
 G.  Extensive self-tests and fault status of each ADF system are available through the Central Maintenance Computer (CMC) (AMM 45-10-00/201), which also receives ADF status from the EIUs.
 2.  Component Details (Fig. 1)_________________
 A.  ADF Receiver
 (1)  
The ADF receivers (2) are located in the center equipment center (E9). This equipment center can be accessed by a door located at the bottom centerline of the fuselage.

 (2)  
The ADF receiver processes the rf signals from the antenna. It operates at the frequency selected on the CDU. The receiver provides bearing and/or audio output signals accordingly.

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