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A

747-400 MAINTENANCE MANUAL 
SEE  A 
28-VOLT AC MAIN SEE C TRANSFORMER 

SEE  B 
28-VOLT AC GROUND SERVICE 
BUS TRANSFORMER 
SEE  C 
P6 MAIN POWER DISTRIBUTION PANEL 
A 
28-VOLT AC 
TRANSFORMER 
(TYPICAL) 

P414 POWER DISTRIBUTION CENTER - LEFT B 
TERMINAL COVER 
C

28-Volt AC Transformer Location
Figure 1

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A
747-400 MAINTENANCE MANUAL
 28-VOLT AC TRANSFORMER - REMOVAL/INSTALLATION
_____________________________________________
 1.  General_______
 A.  This section has two tasks. One task is the removal of the 28-volt ac main transformer (T94) and the 28-volt ac ground-service bus transformer (T150). The other task is the installation of the transformers.
 B.  The installation task includes an operational test of the transformers.
 C.  The main transformer is installed in the P6 panel. The ground-service bus transformer is installed in the P414 panel.
 TASK 24-53-01-004-001
 2.  28-Volt AC Transformer Removal (Fig. 401)______________________________
 A.  References
 (1)  
24-22-00/201, Manual Control

 (2)  
IPC 24-53-01 Fig. 1

 (3)  
IPC 24-53-06 Fig. 1

 (4)  
WDM 24-53-21, 24-53-32

 (5)  
SSM 24-53-01, 24-53-02

 B.  
Access

 (1)  
Location Zone 117 Electrical and Electronics Compartment, LH 222 Control Cabin, RH

 (2)  
Access Panel
 P6 Main Power Distribution Panel
 P414 Power Distribution Center - Left

 C.  
Procedure

 S 864-002
 (1)
Make sure all electrical power is off (Ref 24-22-00/201).

 S 014-003

 (2)
Open the applicable panel to get access to the transformer.

 ~.......................... | Equipment Number | ............................ | Transformer | Panel | ............................ | T94 | P6 | | T150 | P414 | 2.............…............1
 S 034-021
 (3)  
Disconnect the electrical leads from the transformer:

 (a)  
Remove the screws, the washers, and the nuts that attach the terminal cover to the transformer.

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A 747-400 MAINTENANCE MANUAL 
SEE  A 
CSEE TRANSFORMER (T94) 28-VOLT AC MAIN 

SEE B
28-VOLT AC GROUND SERVICE
BUS TRANSFORMER (T150)

SEE C
P6 MAIN POWER DISTRIBUTION PANEL A
28-VOLT AC TRANSFORMER (TYPICAL)
TERMINAL NUT AND WASHER (3 PLACES)
P414 POWER DISTRIBUTION CENTER - LEFT
NUT
B
(2 PLACES)FLAT WASHER LOCK WASHER
(2 PLACES)
(2 PLACES) SCREW
TERMINAL
(2 PLACES)
COVER
C NOTE: TERMINAL LEADS
NOT SHOWN FOR CLARITY.
28-Volt AC Transformer Installation Figure 401
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