(e)  
Attach a breakout box to the rack connector where the black box was installed.

 CAUTION: DO NOT ATTACH LIVE CIRCUIT CABLES TO THE INPUT OF THE TDR.
_______ VOLTAGES MORE THAN 5 VOLTS CAN CAUSE DAMAGE TO THE SAMPLING GATE OR TUNNEL DIODE.
 (f)  Connect the adapter cable from the TDR to the applicable test points on the breakout box.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 20-11-31
 ALL  ú ú 06 Page 203 ú Feb 18/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

747-400
MAINTENANCE MANUAL

DISTANCE FROM
LIQUID
START OF CABLE
CRYSTAL
CURSOR TO CURSOR
DISPLAY

CABLE  COEFFICIENT  PER DIVISION  OF VP  VALUE  OF VP  VALUE 
CONNECTION 
TDR FRONT PANEL 

Time Domain Reflectometer Controls
Figure 201

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 20-11-31
 ALL  ú
 ú  01  Page 204
 ú  Oct 10/91 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 (g)  
Connect a 50 ohm terminator to the open end of the applicable cable.

 (h)  
Set the NOISE FILTER on the TDR to 1 avg.

 (i)  
Set the VERT SCALE to 500 mp.

 (j)  
Set the DIST/DIV switch to show the full cable length.

 NOTE: For example, for a 20 foot cable it will be necessary
____ to have 4 divisions on the display if you use 5 ft/DIV. If you do not know the cable length, set the DIST/DIV to 200 ft/DIV and continue to decrease the DIST/DIV until you see the full waveform. With a 50 ohm terminator attached, the applicable cable will show as a length of no limit.
 (k)  Set the Vp controls for the applicable cable.
 NOTE: The left control is the first number and the right
____ control is the second number of the Vp value.
 (l)  Make allowance for the adapter cable and breakout box.
 1)  Measure the distance from the BNC on the TDR to the start of the applicable cable.
 NOTE: This is the length of the adapter cable.
____
 2) Turn the NOISE FILTER control to HORZ SET REF. 3) Turn the <>POSITION control to move the cursor until the
 distance shown is equal to the adapter cable length. 4) Push STORE. 5) Turn the NOISE FILTER control to 1 avg. 6) Make sure you see 0.000ft. on the LCD.
 NOTE: This is the start of the applicable cable.
____
 S 282-003
 (2)  Examine the applicable cable (Fig. 202):
 (a)  
Examine the waveform shown on the LCD.

 (b)  
Make sure you have a straight line waveform equal to the length of the applicable cable (if known).

 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 20-11-31
 ALL  ú ú 05 Page 205 ú Feb 18/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

747-400
MAINTENANCE MANUAL

TEST PULSE
RISE IN IMPEDANCE CAUSED
LEAVING TDR REFLECTED

BY FRONT PANEL CONNECTOR
PULSE
SEE
O
O N
O F F
O F F
O F F
WAVEFORM
NOISE CAUSED BY NEARBY ELECTRICAL
EQUIPMENT, CAN BE REDUCED WITH
THE NOISE FILTER

O N
O F F
O F F
O
O F
F F
F

USUAL CABLE CONDITIONS

Time Domain Reflectometer Displays
Figure 202 (Sheet 1)

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 20-11-31
 ALL  ú ú 01 Page 206 ú Oct 10/91
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
　
中國航空網 www.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：747-400 AMM 飛機維護手冊 STANDARD PRACTICES - AIRFRAME(85)