S 765-031
 (9)
Make sure the resistance is between 1425 and 1575 ohms.

 S 085-031

 (10)
 Disconnect the multimeter.

 S 485-032

 (11)
 Connect the multimeter between pins 1 and 4 of D4154P.

 NOTE: This step measures the resistance in overheat loop B.
____
 S 765-033
 (12)
 Make sure the resistance you measure is between 1425 to 1575 ohms.

 S 085-033

 (13)
 Disconnect the multimeter.

 S 085-208

 (14)
 Disconnect terminal stud No. 8 from the TS681, TS682 and TS683 loop A detectors.

 S 485-174

 (15)
 Connect the ohmmeter between the terminal studs No.8 and No.10 on the detector, TS681, loop A.

 S 975-175

 (16)
 Measure the resistance of the detector, TS681, (loop A).

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747-400 MAINTENANCE MANUAL
 S 715-137
 (17) Make sure the resistance is in the range shown below.
 ~............................................ | DETECTOR | RESISTANCE (OHMS) | .............................................. | TS681 | 4500 +/- 225 | .............................................. | TS682 | 4500 +/- 225 | .............................................. | TS683 | 4500 +/- 225 | .............................................. | TS684 | 1500 +/- 75 | 2..............….............................1
 S 765-216
 CAUTION:_______A 100VDC MEGGER VOLTAGE IS RECOMMENDED. A 250VDC MEGGER VOLTAGE IS RECOMMENDED ONLY IF THE ELEMENT HAS BEEN CLEANED.
 (18) Use a dc power supply (apply no more than 250VDC between stud and case) to measure the resistance between one of the two terminal studs and the metal case.
 NOTE: Insulation readings vary greatly if element is dirty.
____ Element should be cleaned if it does not meet the insulation requirement.
 (a)  Make sure the resistance is greater than 20 megohms (open circuit).
 S 025-085
 (19)
 Replace the detector if the resistance value is out of the range (AMM 26-11-02/401).

 (20)
 Disconnect the ohmmeter from the detector TS681 (loop A).

 S 085-209

 (21)
 Disconnect terminal stud No. 8 from the loop B detectors of TS681, TS682 and TS683.

 (22)
 Do the procedure again for the detector TS681 (loop B).

 (23)
 Do the procedure again for detectors TS682 through TS684.

 S 085-124
 S 915-131
 S 915-176
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747-400 MAINTENANCE MANUAL
 S 415-210
 (24)
 Connect the terminal stud No. 8 for both loops A and B for detectors TS681, TS682 and TS683.

 S 415-132

 (25)
 Connect the electrical connector D4230P and D4154P on the raceway panel which is on the top of the engine.

 S 765-046

 (26)
 Do the system test again for the other engines.

 K. Put the airplane back to its usual condition.
 S 415-047
 (1)  
Close the thrust reverser half (AMM 78-31-00/201).

 S 865-075

 (2)  
Close the circuit breakers and remove DO-NOT-CLOSE tags:

 (a)  P6 Main Power Distribution Panel 1) 6H1 FIRE EXTINGUISHER ENG 1&3 A 2) 6H2 FIRE EXTINGUISHER ENG 1&3 A 3) 6H3 FIRE EXTINGUISHER ENG 1&3 B 4) 6H4 FIRE EXTINGUISHER 2&4 A 5) 6H5 FIRE EXTINGUISHER APU 6) 6H6 FIRE EXTINGUISHER LOWER CARGO 7) 6C6 FIRE SW UNLOCK (COMBI or FREIGHTER) or
 6H7 FIRE SW UNLOCK (PASSENGER)
 S 865-128
 (3) Remove electrical power if it is not necessary (AMM 24-22-00/201).
　
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