NMEA stops and starts at random (garmin GPS 12)
 

I have a garmin gps 12 that is connected to a raymarine interface and
then to a com port on the PC. Last year everything worked perfect. This
year the green LED in the interface (NMEA-led) stops and start when he
wants.
I cleaned all contacts, checked all the wires, stopped the PC and the
DSC radio, but nothing helps.
I called a technician. He said something about the minus (-) is
connected to the ??? in the pc. I needed a special device to solve that.

Has anybody more info about that error??

Geert Maene