K79843 K80009
Compass System Schematic  5C8 
34-21-0  Figure 5 (Sheet 1)  Jun 20/83 
Page 10 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

5C8  Compass System Schematic 
Jun 20/83  Figure 5 (Sheet 2)  34-21-0 
Page 11 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

COMPASS SYSTEM -TROUBLE SHOOTING
EFFECTIVITY
WA N4502W thru N4530W GJ ALL EXCEPT B-25l09 and B-25110
1.  General
A.  The location of troubles in the compass system can best be determined by a systematic functional test. Use of unit electrical schematics, block diagrams, and electronic wiring diagrams of the compass system will aid in trouble shooting analysis. Trouble shooting the compass system is best accomplished by substituting components where possible.
B.  The flux valve (remote compass transmitter) is extremely sensitive to magnetic fields and will malfunction if it is near magnetic materials which distort the earth's magnetic field.
CAUTION:  DO NOT CHECK THE FLUX VALVE WITH AN OHMMETER. DIRECT CURRENT IN THE WINDINGS MAY MAGNETIZE THE CORES.
C.  Before proceeding with the trouble shooting procedures, recheck that the compass transfer switch is in normal position and all compass system circuit breakers are closed. Check that cable connectors are properly mated and securely connected. Check that 400 cycle ac synchro excitation is present to all units. When substituting known good units in place of suspected malfunctioning units, leave replacement units in the circuit until trouble is cleared and then replace original good units into the operating system.
D.  The following trouble shooting procedures are for compass system No. 1. If trouble is encountered in compass system No. 2, use the same procedure substituting, in the procedure, with an equivalent compass system No. 2 component.
May 01/01 34-21-0 Page 101
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TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
Capt’s HSI compass card does not repeat F/O’s RMI compass card F/O’s RMI compass card will not drive or gives erratic readings F/O’s RMI will not synchronize Capt’s HSI and F/O’s RMI compass cards do not indicate airplane heading  Instrument amplifier No. 1, capt’s HSI, F/O’s RMI Servo amplifier No. 1 or F/O’s RMI Directional gyro No. 1 Servo amplifier No. 1 F/O’s RMI Servo amplifier No. 1 or F/O’s RMI  Rotate F/O’s RMI synch knob; capt’s HSI compass card does not respond to F/O’s RMI readings If replacement of components failed to correct trouble, check airplane wiring Rotate F/O’s RMI synch knob; F/O’s RMI compass card does not respond F/O’s RMI compass card responds to synch knob rotation but gives erratic readings Rotate F/O’s RMI synch knob toward dot or plus F/O’s RMI compass card does not respond to synch knob rotation F/O’s RMI compass card rotates but does not return to synchronized position Place compass transfer switch in ALTERNATE or BOTH ON 2 position  Replace instrument amplifier No. 1 Replace capt’s HSI Replace F/O’s RMI Replace servo amplifier No. 1 Replace F/O’s RMI Replace directional gyro No. 1 Replace servo amplifier No. 1 Replace F/O’s RMI 

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34-21-0  May 01/75 
Page 102 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
Slaving amplifier No. 1 or directional gyro No. 1 F/O’s RMI Damaged airplane wiring  Capt’s HSI and F/O’s RMI compass cards do not indicate capt’s RMI heading If capt’s HSI and F/O’s RMI compass cards indicate capt’s RMI heading, perform following procedure Place compass transfer switch in NORMAL position. Rotate F/O’s RMI synch knob. Set compass card 6 to 10 degrees from synchronized reading Capt’s HSI and F/O’s HSI compass cards do not return to synchronized reading Capt’s HSI and F/O’s RMI compass cards return to synchronized reading (not airplane heading) If above isolation procedure failed to correct trouble, replace components in order listed If replacement of components failed to correct trouble, check airplane wiring CAUTION DISCONNECT FLUX VALVE BEFORE MAKING CONTINUITY CHECKS TO THE FLUX VALVE AIRPLANE WIRING  Replace servo amplifier No. 1 Replace F/O’s RMI Replace slaving amplifier No. 1 Replace directional gyro No. 1 Replace F/O’s RMI Directional gyro No. 1 Flux valve No. 1 Refer to electronic wiring diagrams 
　
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