Repair And Replacement; Replacing The Towfish Pcb - C-Max CM2 User Manual

CM2 Sidescan Sonar User Manual

12. Repair and Replacement

12. REPAIR AND REPLACEMENT

Replacing the Towfish PCB

The towfish internally contains only lead ballast and a single printed circuit board (PCB). This PCB can be
replaced as a unit by the user. Note that this PCB is complex and is not user-serviceable. Any attempted
repair of this PCB by the user will invalidate the warranty and may cause permanent damage.
The towfish should be opened and resealed only in low or moderate humidity conditions to avoid the
possibility of condensation forming internally when the towfish is immersed in cold water.
It is assumed that the tow cable and safety lanyard have been disconnected.
Dismantling the towfish is easier if someone is available to hold it in position, resting with its nose and keel
on a bench, with the keel held upright.
Set the transducer depression angle to 10º and temporarily put cable ties through the slots shown on the
illustration. This secures the transducers to the keel.
Disassembled Towfish
Remove the two M5 socket cap head screws at the forward end of the keel. This is easier if the towfish tube
is pressed down on the keel to keep pressure off the screws.
Push the tube forward and then disconnect the two transducer connectors. Completely separate the tube
assembly from the keel/transducer assembly. The rear bulkhead is now free to be extracted from the tube,
but it will be retained by the grip of the O-rings. Rotate the rear bulkhead to loosen this grip, pulling outwards
at the same time. If necessary use two large screwdrivers, with their blades in the recesses each side of the
rear bulkhead, to start the extraction process.
Note that in cold conditions the rear bulkhead may be released more easily from the grip of the O-rings if the
tube is heated near the joint, for example by pouring hot water over this area. Note also that if the rear
bulkhead and the tube become misaligned (i.e. off axis) they may tend to jam together.
When withdrawing or inserting the PCB (attached to the rear bulkhead) do not allow the black aluminium
heatsink on the end of the PCB to scratch the sealing surface of the tube.
Version 3.6 (2008)
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