Hello Mike & Senormechanico,
I had the exact same issue that Mike had, the unit kept steering
to port. I followed up with Mike to find out if/how he resolved it. He said it was an electrical
connection problem (not surprised, they usually are).
So I tried a direct connect to the battery
to isolate the problem, however, it still steered to port, but this eliminated a possible bad power suppy connection.
I then measured the voltage coming out of the motor
drive terminals on back of the control/diplay unit, it was intermittently sending the same polarity voltage which the drive motor obligingly interpreted as an intermittent signal to turn to port. So this indicated the problem was with the control/display unit.
So I removed the unit and the flux gate compass and took it home and dissassembled it on the kitchen table. I had a look at the power transistors as Senormechanico mentioned, sure enough, I could see where the solder joints had failed.
These switch control transistors are power MOSFETS, and you can tell that they give off heat when operating because Raytheon
has them mounted on a metal bar as a heat sink.
However, over time, the constant heating/cooling of the MOSFEts during operation results in fatigue of the solder joints becasue of the thermal mechanical stress of heating/cooling.
Long and short of it is, I re-soldered the transistor contacts as Senormechanical advised, and lo and behold, the unit is working again.
So thanks for your help guys.