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TASK 77-21-01-766-008-N00
3. EGT Thermocouple Probe Continuity and Insulation Resistance Check (Fig. 601)
_________________________________________________________________
A. Standard Tools and Equipment
(1)
Electronic Multimeter - Model 2795: Simpson Electric Co., American Gage and Machine Co., (Kathy Industries Inc), 853 Dundee Avenue, Elgin, IL 60120
(2)
Heat Gun - capable of 700°F (371°C) maximum heat range
B.
References
(1)
AMM 77-21-01/401, Exhaust Gas Temperature (TT4.95) Thermocouple Probe
(2)
AMM 77-21-01/701, Exhaust Gas Temperature (TT4.95) Thermocouple Probe
(3)
IPC 77-21-01, Fig. 5
(4)
IPC 77-21-03, Fig. 1
C.
Access
(1)
Location Zone 412 Engine 1 - Turbine Exhaust Case 1, 4, 7, or 10 o'clock 422 Engine 2 - Turbine Exhaust Case 1, 4, 7, or 10 o'clock 432 Engine 3 - Turbine Exhaust Case 1, 4, 7, or 10 o'clock 442 Engine 4 - Turbine Exhaust Case 1, 4, 7, or 10 o'clock
(2)
Access Panel
417 Left Core Cowl Panel - Engine 1
418 Right Core Cowl Panel - Engine 1
427 Left Core Cowl Panel - Engine 2
428 Right Core Cowl Panel - Engine 2
437 Left Core Cowl Panel - Engine 3
438 Right Core Cowl Panel - Engine 3
447 Left Core Cowl Panel - Engine 4
448 Right Core Cowl Panel - Engine 4
D.
Procedure
(1)
Clean the EGT probe (AMM 77-21-01/701).
(2)
Apply heat at the junctions of the EGT probe with a heat gun.
S 116-009-N00
S 886-010-N00
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////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
S 766-011-N00
(3) Do a continuity check in circuits A and B at the terminal studs.
NOTE:____ If the needle on the meter moves, there is continuity in the EGT (TT4.95) thermocouple circuits.
(a) If the needle does not move, replace the EGT probe (AMM 77-21-01/401).
S 766-012-N00
(4) Do an insulation resistance check between the chromel terminal stud and the body of the EGT probe (for a minimum of 25 seconds). (a) Make sure the resistance is more than 50,000 ohms (minimum). (b) Replace the EGT probe if the resistance is less than 50,000 ohms (AMM 77-21-01/401).
S 766-016-N00
(5) Do an insulation resistance check between the alumel terminal stud and the body of the EGT probe (for a minimum of 25 seconds). (a) Make sure the resistance is more than 50,000 ohms (minimum). (b) Replace the EGT probe if the resistance is less than 50,000 ohms (AMM 77-21-01/401).
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