20-41-01
ALL ú ú 01 Page 205 ú Oct 10/95
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
GROUNDING LUG
SEE A
SEE B
HINGE (3 LOCATIONS)
FWD
NOSE GEAR SHOCK STRUT
A
SHOCK STRUT LINKAGE OUTBOARD DOOR ROD
GROUNDING SHOCK POINT STRUT
BODY GEAR SHOCK STRUT DOOR LEFT SIDE (RIGHT SIDE IDENTICAL BUT OPPOSITE)
B
Static Grounding Point Location Figure 201
E00605
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20-41-01
ALL ú ú 01 Page 206 ú Oct 10/94
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
ELECTROSTATIC DISCHARGE SENSITIVE DEVICES - MAINTENANCE PRACTICES
_________________________________________________________________
1. General (Fig. 201)_______
A. This procedure contains these tasks:
(1)
Electrostatic Discharge Sensitive (ESDS) printed circuit board removal.
(2)
ESDS printed circuit boards installation.
(3)
ESDS metal encased units removal handling.
(4)
ESDS metal encased units installation handling.
(5)
Wire Integration Unit (WIU) covers removal.
(6)
WIU covers installation.
B. Many electronic line replaceable units (referred to as LRUs) contain micro-circuits and other sensitive devices which can be damaged internally by electrostatic discharges. These LRUs are identified as Electrostatic Discharge Sensitive (referred to as ESDS). The placards installed on the ESDS LRUs show that you must be careful. The persons who remove, install, and move the ESDS LRUs must know about static electricity and the protection from static discharges that is necessary.
C. Electrostatic charges can be caused by these: human bodies, hair, clothing, floors, equipment racks, and equipment units. An electrostatic discharge is electrostatic energy transmitted between materials of different electrical potentials. Electrostatic discharges from nylon clothing or human hair onto polyethylene or steel can cause damage to ESDS components. Damage to the internal components of an ESDS LRU can cause failure with one static discharge. System properties can change with time because of many static discharges.
D. The function of these procedures is to show the maintenance persons how to know and touch the ESDS LRUs. These procedures contain the precautions that are necessary to safely touch the units that are identified by the ESDS placard. Three types of decals are in used to identify the units with ESDS sensitive circuits. The military and commercial symbols are used on some units, while the international (JEDEC) symbol is used on most ESDS placard (Fig. 201). The ESDS printed circuit boards that are LRU's are identified with a "STATIC SENSITIVE" placard (Fig. 201).
TASK 20-41-02-002-053
2. ESDS Printed Circuit Boards - Removal_____________________________________
A. Equipment
(1)
Conductive Bags (Commercially Available)
(2)
Conductive Plastic Carrier (Commercially
Availavle)
(3)
Ohmeter
(4)
Wrist Straps, Conductive (Commercially
Availavle)
(5)
100% Cotton Twine - Commercially Available
(6)
ESDS Labels
(a)
JEDEC International Label - multi-source
(b)
3M - No. 7102
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20-41-02
ALL ú ú 01 Page 201 ú Feb 15/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
STATIC SENSITIVE
TYPICAL BOEING ESDS DECALS
Static Discharge Sensitive Devices Identifiers
Figure 201
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