500 Exhaust Gas Temperature Indicating System
Feb 01/75 Figure 1 77-21-01
Page 3
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
Exhaust Gas Temperature Indicating System Circuit 504
77-21-01 Figure 2 Oct 20/86
Page 4
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
EXHAUST GAS TEMPERATURE INDICATING SYSTEM (SERVOED) - TROUBLE SHOOTING
500
Feb 01/95 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 77-21-01 Page 101
EXHAUST GAS TEMPERATURE INDICATING SYSTEM (SERVOED) -ADJUSTMENT/TEST
1. General
A. The exhaust gas temperature (EGT) indicating system is tested using a millivolt source. Tests include measurements of voltage.
B. Three operational tests are provided which may be used optionally to establish integrity of exhaust gas temperature indicating system. None of the tests provide sufficient accuracy for system calibration, and are to be used only to indicate whether system operation is or is not satisfactory. Operational test No. 1 is preferred if conditions allow.
2. Equipment and Materials
A. Low voltage ohmmeter capable of measuring resistance of 100,000 ohms. Meter should utilize less than 40 volts (dc) and should have accuracy of 5%
NOTE: Low-powered digital meters may give a misleading indication when attempting to measure extremely high or infinite resistances. Analog meters operate at higher voltages and are preferred to digital meters.
B. DC power source variable from 0 to 50 millivolts - Model BH153, Howell Instruments, Fort Worth, Texas
C.
DC millivolt meter capable of measuring to士 0.01 millivolt
D.
Portable container of ice or accurate thermometer
E.
Soldering iron, heat blower gun or other suitable heat source
500
Feb 01/95 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 77-21-01 Page 501
3. Test Insulation Resistance
A. Check thermocouple leads, from indicator to engine terminal strip, for short to ground.
(1)
Disconnect plug from exhaust gas temperature indicator on engine instrument panel.
(2)
Open left engine cowl panel (Ref 71-11-11).
(3)
Disconnect indicator leads (Alumel - green and Chromel -white) from terminal strip (Fig. 501).
(4)
Connect one side of ohmmeter to one of the leads and the other side of ohmmeter to ground.
(5)
Check lead for short to ground. The resistance shall not be less than 100,000 ohms.
(6)
Repeat steps (4) and (5) for the other lead.
(7)
Remove ohmmeter and connect leads to terminal strip.
(8)
Connect plug to the indicator.
B. Check thermocouple harness and leads for shorts to ground.
(1)
Disconnect harness leads from the engine terminal strip (Fig. 501).
(2)
Connect one side of ohmmeter to one of the harness leads and the other side of ohmmeter to ground.
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