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A second method is to connect a several-turn wire loop across the scope probe and move it over
the transducer face. Electrical pickup should be noticed on the scope screen at each transmission
burst. Remember that the transducers and elements within the transducer may be firing together
or in sequence. One must make sure that the electrical pickup is not from an adjacent string.
7.2.2.2
Sonar Processor and Data Link
It is assumed that the sonar processor is up and working in order to complete system test and
troubleshooting. Refer to the sonar processor’s manual for its troubleshooting and diagnostic
information.
The other thing is that the high-speed data must be up and running so that the topside and sub-
sea units are communicating with each other. If the towfish boots up correctly and passes its
internal self-test, there will be a smooth sequence of rising tones going from 2 to 3.9 kHz. A set
of tones jumping from 2 to 3 kHz means that self-test has failed. These tones are generated in the
4200-FS towfish and replicated on the surface when an EdgeTech topside processor is used to
access the Towfish computer subsystem using the Remote Desktop application. The Self Test
PASS tones repeat until data linkup has occurred between the topside Discover software, and
towfish. Self Test FAIL tones repeat indefinitely.
There will also be a video acknowledgement of successful self-test and linkup in the topside
processor's Discover display window. Self-test status will also be displayed on an external video
monitor if attached directly to the towfish’s CPU board's VGA connector.
If the topside processor is unavailable and the towfish is dismantled, an external keyboard,
mouse and video monitor may be connected to the towfish’s CPU board to provide some
diagnostic testing. An external power unit will still be required.
7.2.2.3
Topside Power Unit
Towfish power is supplied either from an individual power/modem unit or from an integrated
topside processor. Voltage and current to the towfish are important parameters. They must be
within acceptable limits for the towfish to work properly. Check the tow cable output voltage
with the system connected and, if possible, the current drain with an inline connection. Cable
current should be between 120mA (Idle) and 250mA.
The topside units supply 400VDC to the tow cable.
The voltage at the towfish end of the cable must be not less than 300VDC to start the system and
not be less than 200V during operation.
7.2.2.4
Command and Data Link
To check that the command and data link over the tow cable is operational, start the Remote
Desktop application on the topside control computer. There is normally a shortcut on the
Edgetech Desktop for this. The towfish's PC screen should appear in a window on the topside
computer screen. This will appear as a yellow desktop with the sonar application dialog box
visible. If this is successful then the command link is working.
