Raymarine C Series NMEA In-Out Voltages

[NOHOH]

I`m trying to track down why my DSC radio is no longer displaying position and time information. My thinking is that it is going to be a fault in either the Raymarine C120 or the Brookhouse AIS C Multiplexer.
The Mux outputs combined NMEA at 38000 which is fed to the Raymarine NMEA in....The Raymarine then outputs NMEA back to the Mux which then converts it back to 4800...and then a seperate Mux output at this bit rate is fed to the DSC radio. Although this arrangement has worked perfectly for over a year..there is now no output from the Mux seperate output.
All connections have been checked/double checked..so I`m convinced its not a wiring fault
However.....measuring the voltage of the NMEA just before it goes into the C120 (at 38000) by putting a multimeter across it ...a fluctuating reading of around 3.5 volts is seen..........but on the output side (also at 38000)...a fluctuating voltage of only around 1.5 volts is seen... and this is what is reaching the seperate input of the Mux......and I was wondering whether this lower voltage output by the Raymarine is somehow not triggering the Brookhouse to output to the seperate output.......or whether its the multiplexer that is at fault...
Any help in identifying whether the Raymarine or the Multiplexer is at fault would be greatly appreciated

 

[colvic987]

I`m trying to track down why my DSC radio is no longer displaying position and time information. My thinking is that it is going to be a fault in either the Raymarine C120 or the Brookhouse AIS C Multiplexer.
The Mux outputs combined NMEA at 38000 which is fed to the Raymarine NMEA in....The Raymarine then outputs NMEA back to the Mux which then converts it back to 4800...and then a seperate Mux output at this bit rate is fed to the DSC radio. Although this arrangement has worked perfectly for over a year..there is now no output from the Mux seperate output.
All connections have been checked/double checked..so I`m convinced its not a wiring fault
However.....measuring the voltage of the NMEA just before it goes into the C120 (at 38000) by putting a multimeter across it ...a fluctuating reading of around 3.5 volts is seen..........but on the output side (also at 38000)...a fluctuating voltage of only around 1.5 volts is seen... and this is what is reaching the seperate input of the Mux......and I was wondering whether this lower voltage output by the Raymarine is somehow not triggering the Brookhouse to output to the seperate output.......or whether its the multiplexer that is at fault...
Any help in identifying whether the Raymarine or the Multiplexer is at fault would be greatly appreciated

Hi, did you find an answer to your c120 problem.

 

[Hoist]

Is it possible to cut the multiplexer out of the equation and feed the DSC straight from the plotter?

If the plotter is still receiving position from the GPS antenna then it must be the multiplexer failed.

Also check the baud rate on everything or make sure settings are as they should be

 

[[164147]]

You can run diagnostics in the C120 to see what NMEA sentences are being sent and received. If the C120 is sending GLL GGA it will be the AIS or DSC or wiring in-between.