Raymarine/Autohelm ST50 Navdata Seatalk problem

[szigi]

Hi,

I've got the following problem: I have an Autohelm ST50 Navdata instrumment, conected to a GPS via its NMEA port. It is further connected to an ST4000 autopilot, via Seatalk. Now, seatalk does not work. Namely, the Navdata instrument does not receive of send any seatalk data. Looking at its seatalk line with an oscilloscope, it starts to send a message, but immediately stops sendig, as if it senses that there is a collision on the bus, even though I had it disconnected. I will further take it apart, and check, but seems to me, that it is not sensing correctly its own communication, and thinks that the seatalk bus is busy. Maybe the bus transciever is faulty?

Has anyone experienced similar problems with this (or other Seatalk instrument)? Maybe someone can help me out with a service manual, or schematics.

Obviously there is no point in sending the unit to Raymarine, as its would probably be cheaper to buy a replacement instrument on ebay.

[szigi]

Just to answer my own question. After spendig a couple of hours reverse engineering, finally found a corroded trace on the PCB, under a SMD chip. Pathced it up, and all is fine and working.