757 AMM 飞机维护手册 STANDARD PRACTICES - AIRFRAME(150)

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 B.  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 substances of different electrical potentials. Electrostatic discharges from nylon clothing or human hair onto polyethylene or steel can damage 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.
 C.  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).
 D.  This procedure contains these tasks:
 (1)
ESDS Printed Circuit Board Removal

 (2)
ESDS Printed Circuit Board Installation

 (3)
ESDS Metal Encased Unit Removal Handling

 (4)
ESDS Metal Encased Unit Installation Handling

 TASK 20-41-01-002-001
 2.  ESDS Printed Circuit Board Removal__________________________________
 A.  Equipment
 (1) Conductive Bags - 3M type 2100
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757 
MAINTENANCE MANUAL 
ELECTROSTATIC 
MAIN EQUIP CTR SHELVES  GROUND JACK 

Static Sensitive Devices Identifiers
Figure 201

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MAINTENANCE MANUAL

Onboard Wrist Strap Stowage
Figure 202

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MAINTENANCE MANUAL

 (2)  
Conductive Plastic Carrier - Electrical
 Insulation Suppliers PCC-700

 (3)  
Ohmmeter

 (4)  
Wrist Straps - 3M 2066 or 2067

 (a)  A wrist strap is kept on the plenum of the racks E3 and E4 in the main equipment center (Fig. 202).

 (5)  
100% Cotton Twine - Commercially Available

 (6)  
ESDS Labels

 (a)  
JEDEC International Label - multi-source

 (b)  
3M - No. 7102

 

 B. Remove the Printed Circuit Boards with the STATIC SENSITIVE placards
 NOTE: The placards on the outer area of the card files show the cards
____ that contain the ESDS printed circuit boards that are LRU's.
 S 862-039
 CAUTION: MAKE SURE YOU KEEP CONTAMINATION OR UNWANTED MATERIAL AWAY FROM
_______ THE SENSITIVE DEVICE. CONTAMINATION OR UNWANTED MATERIAL NEAR THE SENSITIVE DEVICE CAN CAUSE A MALFUNCTION IN THE SENSITIVE DEVICE.
 (1)  Remove the system electrical power with the applicable
 Removal/Installation procedure.

 S 862-037
 WARNING: USE A WRIST STRAP WITH A MINIMUM GROUNDING LEAD RESISTANCE OF
_______ 250 KILOHMS AND A MAXIMUM OF 1.5 MEGOHMS. USE OF A LOW RESISTANCE WRIST STRAP CAN CAUSE INJURY TO PERSONS IF A HIGH VOLTAGE SOURCE IS TOUCHED.
 (2)  Do these steps to do a test of the wrist strap resistance:
 (a)  
Use an ohmmeter to make sure the wrist strap assembly has a minimum resistance of 250 kilohms and a maximum of 1.5 megohms.
　
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