TM 55-1905-223-24-14
The gyro control and power assembly receives its operating 24 Vdc normally from the power converter through the power
transfer unit and in an emergency, from the ship's 24 Vdc source. The switch unit (Sheet 3) receives dc power from the
gyro control and power assembly. It amplifies the power to the two open scale repeaters. Another output from the switch
unit is applied to the relay transmitter (Sheet 4). The relay transmitter receives 120 Vac, single phase, 60 Hz power from
the pilothouse IC/ELEX panel. This assembly converts the ship's ac input power to +70 Vdc output for the repeaters. The
unit also provides dc output distribution for the amplified compass step data. In the event of an overload on any channel
output, the data for that particular channel is turned off automatically by internal circuitry-and the alarm lamp on circuit
card A1 lights. When the overload has been removed, such as by turning off the defective channel, the overload circuit
automatic-ally resets itself with the next change in input data. However, the overload lamp will remain on until the reset
switch A1S1 is depressed. This will alert maintenance personnel to momentary overloads which might otherwise go
unnoticed. The open scale repeaters (Sheet 5) receive step data power and 70 Vdc supply from the switch unit through
the bulkhead mounting bracket. The bearing repeaters (Sheet 6) receive step data, power, and 70 Vdc from the relay
transmitter through the pelorus stand. The stand contains a rheostat for controlling the 70 Vdc lamp power.
b. Slew Mode. The SLEW position of the mode selector switch gives the operator manual control of the gyro
compass. The compass card can be slewed in either direction using the tilt/azimuth switch. The slew signal is routed to
the servoamplifier for amplification to drive the azimuth motor. The gyro does not run, the CAGED lamp is illuminated,
and the, cager is engaged in the slew mode. Resistor R10 develops the input voltage for slewing and sets the rate at
which the compass slews.
WARNING
To prevent personal injury, the gyro must be caged to prevent tilt while
the gyro comes up to speed. Use caution when leveling the gyro since
uncaging enables it to tilt.
c. Start Mode. With the mode selector switch in START position, power is applied to the gyro motor. Once the
wheel is brought up to speed, the gyro is uncaged and manually leveled using the level meter. A special start circuit
establishes a three-phase voltage sequence when the gyro is starting, because impedance of the motor windings when
the gyro is starting and accelerating is appreciably different from impedance of the motor when the gyro is up to speed.
The 120 volt, 60 Hz winding of transformer T2 in the power supply is the source of power for the start circuit and gyro
motor. While the gyro motor is coming up to speed, the vertical ring and sphere are caged to prevent tilt and the
compass is slewed to heading. Once the gyro has developed sufficient momentum it is uncaged.
d. Run Mode. Normal operation of the gyro compass takes place when the mode selector switch is at RUN
position. All circuits operate the same as in start mode except any output from the tilt/azimuth switch is shorted to
ground. This protects the compass against being upset by accidental operation-of the switch after the compass has
started to settle. The pickoff signal is coupled to the servoamplifier, and the amplifier increases the signal and drives the
azimuth motor. Output of the servoamplifier is also fed to the alarm circuit to provide an indication if follow-up system
failure should occur.
1-28
Previous Page
