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Remember that the transducers and elements within the transducer may be firing together or in
sequence. Make sure that the electrical pickup is not from an adjacent string.
5.5.3 Sonar Processor and Data Link
It is assumed that the sonar processor is up and working to complete system testing and troubleshooting.
Refer to the sonar processor’s manual for its troubleshooting and diagnostic information.
The high-speed data must also be up and running so that the topside and sub-sea units are communicating
with each other. If the tow vehicle 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 the self-test has failed.
These tones are generated in the software of the 4200-Tow Vehicle. They are replicated on the surface
when an EdgeTech topside processor is used to access the tow fish computer subsystem using the Remote
Desktop application. The Self-Test PASS tones repeat until data linkup has occurred between the topside
Discover software and tow fish. Self-Test FAIL tones repeat indefinitely.
There will also be a video acknowledgment 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 is attached
directly to the tow fish’s CPU board's VGA connector.
If the topside processor is unavailable, and the tow fish is dismantled, an external keyboard, mouse, and
video monitor may be connected to the tow fish’s CPU board to provide some diagnostic testing. An
external power unit will still be required.
5.5.4 Topside Power Unit
Tow fish power is supplied either from an individual power/modem unit or from an integrated topside
processor. Voltage and current to the tow fish are important parameters. They must be within acceptable
limits for the tow fish 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 tow fish end of the cable must be not less than 300VDC to start the system and not be
less than 200V during operation.
5.5.5 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 tow fish's PC screen will 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, the command link is
working.
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