2. External Power Receptacle Check
A. General
(1) Repeated use, particularly in dusty localities, results in receptacle pin and plug socket wear which can cause poor electrical contact and overheating. Receptacle pin overheating can also be caused by loose or corroded connections of the electrical conductors to the inner ends of the pins. Wear, overheating and resulting oxidation along with corrosion, all cause pin and socket dimensions to change. Therefore, scheduled periodic checks of receptacle pins and ground power plug sockets should be made.
B. External Power Receptacle Pins Check
(1)
General
(a) The 115 volt, 3 phase external power receptacle contains four ac input circuit pins
0.435 to 0.437 inch in diameter and two dc control circuit pins 0.310 to 0.312 inch in diameter. The six pins are fixed in an insulating plastic base and are threaded on the inboard ends to provide for connecting electrical cables. The pins are not removable for individual replacement. A damaged or undersized contact pin will require replacing the insulating support base containing the six pins.
(2)
Equipment and Materials
(a) Ground Power Plug and Receptacle Wear Gauge Set - F70284-1 consisting of the following: 1) F70284-2, wear gage, ac power pin 2) F70284-3, wear gage, dc power pin 3) 1N-25, instrument scale
NOTE: The Wear Gage Set - F70284-1 is also used to check the external power unit (ground power supply) plug sockets.
(3) Check external power receptacle pins.
(a)
Open GND SERV circuit breaker on right load control center P6 and push battery switch on overhead panel P5 to OFF.
(b)
Check ac pins.
1) Try to put wear gage F70284-2 on AC pin A.
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CAUTION: DO NOT USE EXCESSIVE FORCE TO PUSH WEAR GAGE ON PINS. THE WEAR GAGE IS A GO NO/GO GAGE AND SHOULD NOT FIT OVER THE PIN. TO MUCH FORCE ON THE PIN CAN CAUSE DAMAGE.
2) Repeat step 1) for pins B, C and N.
3) If any pins fail to pass test or are otherwise deformed, insulating support base including six pins should be replaced.
(c) Check dc pins.
1) Try to put wear gage F70284-3 on DC pin E.
CAUTION: DO NOT USE EXCESSIVE FORCE TO PUSH WEAR GAGE ON PINS. THE WEAR GAGE IS A GO NO/GO GAGE AND SHOULD NOT FIT OVER THE PIN. TO MUCH FORCE ON THE PIN CAN CAUSE DAMAGE.
2) Repeat step 1) for pin F.
3) If any pins fail to pass test or are otherwise deformed, insulating support base including six pins should be replaced.
(d) Close GND SERV circuit breaker panel on P6.
3. External Power Receptacle Neutral Pin to Main Landing Gear Grounding Stud Continuity Check
A. General
(1) This check examines for continuity between the neutral pin on the external power receptacle and the ground stud located on the airplane main landing gear.
B. Neutral Pin to Grounding Stud Continuity Check
(1)
Equipment and Materials
(a) Low Resistance Ohmmeter
(2)
Prepare to check the continuity between the receptacle pin and the main landing gear grounding stud.
(a)
Remove electrical power from the airplane.
(b)
Open the door to access the external power receptacle.
(3)
Check the continuity between the receptacle neutral pin and the main landing gear grounding stud.
(a)
Use the low resistance ohmmeter to measure the resistance from the neutral pin on the external power receptacle to the main landing gear grounding stud.
(b)
Make sure the resistance does not exceed 0.1 ohms.
(c)
If the resistance exceeds 0.1 ohms, examine the external power receptacle for damage according to the external power receptacle inspection described above.
(d)
If the problem continues, examine and repair the wiring between the external power receptacle neutral pin and the associated ground stud.
(4)
Put the airplane back to its usual condition.
(a) Close the access door for the external power receptacle.
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BUS PROTECTION PANEL - REMOVAL/INSTALLATION
1. General
A. This procedure contains two tasks. The first task is the removal of the bus protection panel (BPP). the second task is the installation of the BPP. After the installation, there is an operational test of the BPP. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：737 AMM 飞机维护手册 电源 ELECTRICAL POWER(61)
