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22. Maintenance and Troubleshooting
22-9
Problem Probable causes or
check points
Remedy
Antenna not rotating 1) Antenna drive mechanism
2) Defective antenna drive motor
relay (thermal relay K2,
200/220/380, 440/100 VAC)
1) Replace antenna drive mechanism.
2) Press relay reset button.
Data and marks not displayed in
Transmit status
SPU board Replace SPU board.
Adjust GAIN with A/C SEA set
at minimum. Marks and
indications appear but no noise
or echo
1) IF amplifier
2) Signal cable between antenna
and processor
unit
3) Video amplifier board
1) Replace IF amplifier.
2) Check continuously and isolation of coaxial
cable.
Note: Disconnect the plug and lugs at both ends
of coaxial cable before checking it by ohmmeter.
3) Check video coax line for secure connection.
If connection is good, replace SPU board.
Marks, indications and noise
appear but no echo
(Transmission leak representing
own ship position is absent)
1) TX fuse
2) Magnetron
3) Modulator board
4) SPU board
1) If fuse is blown, replace it. If it blows
again, the modulator or associated
circuit may be defective.
2) Check magnetron current.
Replace magnetron.
3) Replace modulator board.
4) Replace SPU board.
Picture not updated or picture
freeze-up
1) Bearing signal generator board
(in antenna unit)
2) SPU board
3) Video freeze-up
1) Check the connection of signal cables.
2) Replace SPU board.
3) Turn off and on the radar.
Incorrect orientation of picture 1) SPU board
2) Gyro interface
1) The message GYRO appears when the
heading pulse is not received during standby.
2) Replace the gyro interface.
Incorrect orientation of picture 1) SPU board
2) Gyro interface
1) The message GYRO appears when the
heading pulse is not received during standby.
2) Replace the gyro interface.
Cannot operate radar from on-
screen boxes
SPU Board Replace SPU Board.