(d)  
Continue to hold the cargo door switch in OPEN position and read the DC voltage on the voltmeter.

 (e)  
If the voltage is 1 volt DC or more, then the shorted diode is in one or more of the remaining latch actuators. 1) If the voltage is less than 1 volt DC, then the shorted

 diode is in this group of latch actuators.

 (f)  
Continue to do a check for the shorted diode in the remaining groups of latch actuators with each of these circuit breakers closed:

 NOTE: Close each circuit breaker and do a voltage check until
____ you find the group of (4) latch actuators that has a shorted diode. You will have to find the defective latch actuator in this group before you do a check for the remaining group (s) of the latch actuators.
 1) LATCHES 1-4L
 2) LATCHES 1-4R
 3) LATCHES 5-8R

 (g)  FOR A GROUP OF (4) LATCH ACTUATORS THAT HAS A SHORTED DIODE; Do these steps to find the defective latch actuator: 1) Open the applicable circuit breaker that contains a shorted
 diode.
 2)  With the door control switch held in OPEN position, manually crank each latch actuator a minimum of 25 turns in the open direction.
 3)  If the voltmeter reads 1 volt DC or more, then the actuator is defective.
 (h)  Replace the defective latch actuator (Ref 52-31-05/401).
 S 085-010
 (4)  
Make sure to remove the voltmeter.

 F.  
Put the Airplane Back To Its Usual Condition

 (1)  
Make sure the door is fully closed, latched and locked.

 S 415-012
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 52-31-05
 ALL  ú ú 02 Page 504 ú Feb 18/00
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 S 865-011
 (2) Remove electrical power, if it is not necessary (Ref 24-22-00/201).
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 52-31-05
 ALL  ú ú 02 Page 505 ú Feb 10/94
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 NOSE CARGO DOOR PORTAL LATCH FITTING - REMOVAL/INSTALLATION
___________________________________________________________
 1.  General_______
 A.  This procedure has two tasks:
 (1)  
The removal of portal latch fittings on the nose cargo door.

 (2)  
The installation of portal latch fittings on the nose cargo door.

 B.  
There are two sets of the portal latch fittings on the nose cargo door: The first set is the actuator-pin portal latch fittings which includes fittings 1-8 L&R. The second set is the fixed-pin portal latch fitting which includes fittings 9-10 L&R and 11.

 C.  
The actuator-pin latch fittings on door structure are not removable or adjustable, but the bearings can be replaced.

 D.  
The fixed-pin latch fittings 9 L&R and 11 on the door structure are not removable or adjustable.

 TASK 52-31-06-004-001
 2.  Portal Latch Fitting Removal (Fig. 401)____________________________
 A.  References
 (1)  
24-22-00/201, Manual Control

 (2)  
52-31-05/501, Nose Cargo Door Latch Actuator

 B.  
Access

 (1)  
Location Zone
 801 Nose Cargo Door

 C.  
Prepare For Removal

 S 864-003
 (1)  
Supply electrical power (24-22-00/201).

 S 864-004

 (2)  
Open the nose cargo door to get access to the portal latch fitting.

 S 864-005

 (3)
Open these circuit breakers and attach the DO-NOT-CLOSE tags:

 (a)  
On the Auxilary External 2 Power Center-Right panel P715: 1) 715XX, NOSE CARGO DOOR

 (b)  
On the Power Distribution Center-Right panel P415: 1) 415F16, NOSE CARGO DOOR CONTROL

 (c)  
On the Nose Cargo Door Power panel H122: 1) DOOR LIFT 2) PULL UP CAM 3) LATCHES 1-4R 4) LATCHES 1-4L 5) LATCHES 5-8R 6) LATCHES 5-8L

　
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