LEFT ICU SHOWN
(RIGHT SIDE OPPSITE)

Interface Control Unit (ICU) - Installation

Figure 401

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747-400 MAINTENANCE MANUAL
 (b)  Right ICU - DM7951A, DM7951B and DM7951C
 S 034-008
 (5)  
Remove the four fasteners from the ICU base.

 S 024-009

 (6)  
Remove the ICU from the support bracket.

 TASK 21-31-10-404-010
 3.  Interface Control Unit (ICU) Installation (Fig. 401)_________________________________________
 A. Equipment
 (1)  (1) Sandpaper, 400 to 600 grit Aluminum Oxide- Commercially available
 B. Consumable Material
 (1)  
G01354 Tape - Vinyl Plastic - 2 inches wide, No. 271

 (2)  
B00148 solvent, Methyl Ethyl Ketone (MEK)

 (3)  
B00316 Solvent - Aliphatic Naptha, TT-N-95

 C. References
 (1)  
AMM 21-31-00/501, Cabin Pressure Control System

 (2)  
24-22-00/201, Manual Control

 (3)  
IPC 21-31-10 Fig. 1

 (4)  
WDM 21-31-12

 (5)  
SSM 21-31-02

 D. Access
 (1)  Location Zone
 151 Area Aft of Bulk Cargo Compartment, LH
 152 Area Aft of BUlk Cargo Compartment, RH

 E. Procedure
 S 424-011
 (1)  
Install the ICU on the support bracket with the electrical receptacles inboard.

 (2)  
Attach the ICU to the bracket with the four fasteners.

 S 434-013

 (3)  
Install the bonding jumper:

 S 434-012
 (a)  Clean the bond surfaces of the ground strap on the ICU as follows: 1) Use 400 to 600 grit aluminum oxide sandpaper to prepare the
 bond surfaces of the ground strap so that all surface finishes are removed and bright metallic bond surfaces are visible.
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 2)  Remove the minimum amount of material necessary to get bright metallic surface.
 (b)  Remove metal particles, dirt and any other contaminants from the bond surfaces as follows: 1) Pour clean, uncontaminated B00148 solvent, Methyl Ethyl
 Ketone (MEK), ASTM D740, onto clean BMS15-5, Class A
 absorbent wipers. 2) Wipe the surfaces with the solvent soaked wiper. 3) Immediately wipe surfaces dry with clean dry wipers until
 all solvent is removed from the surfaces. 4) Repeat the above three steps until the wiper shows no visible contamination or discoloration.
 (c)  Install the bonding jumper, bolt, three washers, and nut onto the ground strap of the ICU.
 NOTE: Make sure the bonding jumper, bolt, washers, and the
____ nut are clean. 1) Tighten the nut to a torque of 60 to 65 inch-pounds (6.8 to
 7.3 Newton-meters).
 2)  Make sure that the resistance between the ground strap and the bonding jumpers is a maximum of 0.01 ohm.
 S 434-014
 (4)  Install the electrical connectors on the ICU.
 (a)  
Left ICU - DM7950A, DM7950B and DM7950C

 (b)  
Right ICU - DM7951A, DM7951B and DM7951C

 S 864-016
 (5)  
Supply electrical power (Ref 24-22-00/201).

 S 864-017

 (6)  
Make sure the air/ground relay system is in the ground mode.

 S 744-018
 CAUTION: MAKE SURE THE PRESSURIZATION OUTFLOW VALVES ARE FREE TO
_______ MOVE. IF THE VALVE FLAPPERS ARE NOT FREE TO MOVE, THE MOVEMENT OF THE VALVES DURING THIS TEST CAN CAUSE DAMAGE TO EQUIPMENT.
 (7)  Do a ground test of the cabin pressure control system at one of the CMC CDUs (AMM 21-31-00/501).
 (a)  
Make sure the AUTO SELECT switch on the P5 overhead panel is on NORM.
　
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