(2)  
Access Panel
 125B Access Door Electronics - Left

 D.  Procedure
 S 865-300
 (1)  
Supply electrical power (AMM 24-22-00/201).

 S 865-301

 (2)  
Close these circuit breakers:

 (a)  P7 Overhead Circuit Breaker Panel
 1) 7B3 RADIO ALT L

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747-400 MAINTENANCE MANUAL
 2) 7B4 RADIO ALT C
 3) 7C21 RADIO ALT R

 S 015-330
 (3)  
Open the access door (125B) on body section 42 to get access to the radio altimeter R/Ts (AMM 06-09-02/201).

 S 745-302

 (4)  
Do the BITE test:

 (a)  Push and release the TEST switch on the front panel of the left RA receiver/transmitter. 1) Make sure the conditions that follow occur:
 a) The TEST IN PROGRESS display is shown on the LCD screen for approximately 5 seconds. b) The TEST COMPLETE NO FAILURES display is shown on the LCD screen for approximately 25 seconds. c) The captain's EADI display shows 40 +/- 2 feet for 30 seconds.
 d)  Approximately 30 seconds after the TEST switch was pressed and released, the P/N and S/W display is shown on the LCD screen and the applicable EADI display shows -6 +/- 2 feet.
 S 745-290
 (5)  Do the BITE test again except do it for the right R/T and then the center R/T.
 E.  Put the Airplane in its Usual Condition
 S 415-329
 (1)  
Close access door 125B if access is not necessary
 (AMM 06-09-02/201).

 (2)
Remove electrical power if it is not necessary (AMM 24-22-00/201).

 S 865-291
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 RADIO ALTIMETER RECEIVER/TRANSMITTER - REMOVAL/INSTALLATION
___________________________________________________________
 1.  General
_______
 A.  This procedure has two tasks, a removal and an installation of the radio altimeter receiver/transmitter (R/T). The installation procedure also has a test of the R/T unit.
 B.  The CMC has a Shop Faults menu item for the R/Ts, but the R/Ts can not give Shop Fault data.
 NOTE: Do not try to get Shop Fault Data from a radio altimeter R/T.
____
 TASK 34-33-02-004-001
 2.  Radio Altimeter Receiver/Transmitter Removal
____________________________________________
 A.  General
 (1)  
There are three R/Ts installed adjacent to each other in the E9 equipment rack in the center equipment center. A knurled clamp-nut holds each R/T in its position.

 (2)  
The removal procedure is the same for each R/T unit.

 B.  References
 (1)  
20-11-22/401, E/E Rack Mounted Components

 (2)  
24-22-00/201, Manual Control

 C.  Access
 (1)  Location Zone
 117 Electrical and Electronics Compartment

 D.  Procedure
 S 864-002
 (1)  Open the circuit breaker for the applicable radio altimeter R/T and attach a DO-NOT-CLOSE tag:
 (a)  P7 Overhead Circuit Breaker Panel
 1) 7B3 RADIO ALTM L
 2) 7B4 RADIO ALTM C
 3) 7C21 RADIO ALTM R

 S 024-026
 CAUTION: DO NOT TOUCH THE CONNECTOR PINS OR OTHER CONDUCTORS ON THE
_______ R/T UNIT. IF YOU TOUCH THESE CONDUCTORS, ELECTROSTATIC DISCHARGE FROM YOUR BODY CAN CAUSE DAMAGE TO THE R/T UNIT.
 (2)  Do this procedure to remove the R/T unit: Remove the E/E Box (Ref 20-11-22/401).
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