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MAINTENANCE MANUAL

 (b)  
Make sure the forward lateral guide rails retract and stay in that position.

 (c)  
Put the LATERAL GUIDE switch in the NORMAL position.

 (d)  
Put the joystick in the FWD or AFT position for the forward compartment to extend the forward lateral guide rails.

 (e)  
Release the joystick to the center when the forward lateral guides are fully extended.

 G. Put the Airplane Back to Its Usual Condition
 S 865-041
 (1)  
Put the POWER DRIVE SYSTEM switch in the OFF position.

 S 095-042

 (2)  
Remove the safety barrier for the cargo door.

 S 415-043

 (3)  
Close the cargo door (AMM 52-34-01/401).

 S 865-044

 (4)  
Remove electrical power if it is not necessary (AMM 24-22-00/201).

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747-400 MAINTENANCE MANUAL
 TRAY MOUNTED POWER DRIVE UNIT - REMOVAL/INSTALLATION
____________________________________________________
 1.  General
_______
 A.  This procedure contains these tasks:
 (1)  
The removal of the power drive unit (PDU).

 (2)  
The installation of the power drive unit (PDU).

 B.  The PDU's provide powered means of moving cargo within the forward and aft cargo compartments. Each PDU has an internal motor, a self-lifting cam, and two rubber covered drive rollers. The PDU's are installed in both the ballmat area and in the roller trays. The procedures that follow are the same for all PDU's.
 C.  References
 D.  AMM 24-22-00/201, Manual Control - Maintenance Practices
 E.  AMM 52-34-00/001, Forward/Aft Cargo Doors - Description and Operation
 F.  IPC 25-53-01, Illustrated Parts Catalog
 TASK 25-53-01-004-001
 2.  Power Drive Unit (PDU) Removal (Fig. 401)
______________________________
 A.  Prepare for the removal
 S 864-002
 (1)  
Supply electrical ground power (AMM 24-22-00/201).

 S 014-003

 (2)  
Open the cargo compartment door (AMM 52-34-00/001).

 S 864-004
 WARNING: USE CARE WHEN WORKING NEAR THE OPENING OF THE CARGO COMPARTMENT
_______ DOOR. INSTALL A SAFETY BARRIER, IF IT IS NECESSARY. INJURY TO PERSONS CAN OCCUR IF THEY FALL THROUGH THE OPENING OF THE DOOR.
 (3)  
Push the CAUTION switch-light on the cargo control panel until it starts to flash.

 S 864-005

 (4)  
Make sure the POWER DRIVE SYSTEM switch on the cargo control panel is in the OFF position.

 S 864-006

 (5)  
Open the circuit breaker, and attach DO-NOT-CLOSE tags, for the applicable PDU.

 (a)  
For the forward compartment, the circuit breaker is on the P86 Forward Lower Cargo Equipment Panel.

 (b)  
For the aft compartment, the circuit breaker is on the P59 Aft Lower Cargo Equipment Panel.

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747-400 MAINTENANCE MANUAL
 B. Remove the PDU
 S 044-007
 (1)  
Disconnect electrical connector and ground strap with two washers, and remove four socket head cap screws.

 S 024-008

 (2)  
Remove PDU from its mounting structure.

 TASK 25-53-01-404-009
 3. Power Drive Unit (PDU) Installation (Fig. 401)
___________________________________
 A. Prepare for the removal
 S 864-010
 (1)  
Supply electrical ground power (AMM 24-22-00/201).
　
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