S 865-141

 (19)
 Put the toggle switch on the squib circuit test box to the OFF position.

 S 865-143

 (20)
 Turn and hold the APU fire handle fully clockwise.

 S 735-144

 (21)
 Make sure the APU BTL DISCH light on the squib circuit test box is on.

 S 975-145

 (22)
 Measure and make a record of the voltage on the multimeter (V1).

 S 865-146

 (23)
 Put the toggle switch on the squib circuit test box to the ON position.

 S 975-147

 (24)
 Make a record of the voltage on the multimeter (V2).

 S 865-148

 (25)
 Release the APU fire handle.

 (a)  Make sure the handle moves quickly to in 10 degrees or less of the center position.

 (26)
 Make sure the multimeter shows 0 | 2 volts.

 (27)
 Turn the handle to the horizontal position.

 (28)
 Push in the fire handle to the usual position.

 S 865-046

 (29)
 Put the toggle switch on the squib circuit test box to the OFF position.

 S 735-149
 S 865-150
 S 865-138
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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A
747-400 MAINTENANCE MANUAL
 S 015-047
 (30)
 Get access to the fire shutdown module for the APU, M869, which is installed in the right wheel well for the main landing gear.

 S 865-048

 (31)
 Pull the fire control handle on the fire shutdown module for the APU, M869.

 S 735-049

 (32)
 Make sure the APU BTL DISCH light on the squib circuit test box is off.

 S 865-050

 (33)
 Push and hold the APU EXTINGUISHER DISCHARGE button on the fire shutdown module, M869.

 S 735-051

 (34)
 Make sure the APU BTL DISCH light on the squib circuit test box is on.

 S 975-052

 (35)
 Make a record of the voltage on the multimeter (V1).

 S 865-053

 (36)
 Put the toggle switch on the squib circuit test box to the ON position.

 S 975-054

 (37)
 Make a record of the voltage on the multimeter (V2).

 S 865-055

 (38)
 Release the APU EXTINGUISHER DISCHARGE button on the M869 module.

 S 735-056

 (39)
 Make sure the multimeter shows 0 | 2 volts.

 S 735-142

 (40)
 Make sure the APU BTL DISCH light on the squib circuit test box is off.

 (41)
 Restore the APU fire control handle to its normal position.

 S 865-226

 (42)
 Open this circuit breaker on the main power distribution panel, P6, and attach a DO-NOT-CLOSE tag:

 S 865-225
 (a) 6H5, FIRE EXTINGUISHER APU
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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 ALL  ú ú 01 Page 509 ú Jun 10/97
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 S 485-057
 (43)
 Remove the squib electrical connector, DM103B, from the squib circuit test box.

 S 865-227

 (44)
 Remove the DO-NOT-CLOSE tag and close this circuit breaker on the main power distribution panel, P6:

 (a)  6H5, FIRE EXTINGUISHER APU
 S 975-058
 (45) Calculate the resistance for the squib discharge circuit, RC, with the formula that follows:
 RC = RL * (V1/V2) - RL
 Make sure the value for RC is less than 3.8 ohms.
 NOTE: If RC is more than 3.8 ohms, the circuit can not supply
____
 sufficient current to fire the squib.

 S 085-074
 (46)
 Remove the wires from the squib circuit test box.

 H.
Do a Fire Simulation Test

 S 865-220
 WARNING: DO NOT TOUCH THE SQUIB BEFORE YOU DO THE PROCEDURES FOR DEVICES
_______ THAT ARE SENSITIVE TO ELECTROSTATIC DISCHARGE. ELECTROSTATIC DISCHARGE CAN CAUSE THE FIRE BOTTLES TO RELEASE ITS CONTENTS SUDDENLY AND CAUSE INJURY TO PERSONS AND DAMAGE TO EQUIPMENT.
　
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