NMEA0183 network down

[Notyetsinking]

Hi,

I have a B&G hydra 2000 networked system with quite a few FFDs and other data attached to it. I disconnected one of the dead FFDs that was still receiving data, and wired in a usb to rs232 cable (3-core)in its place at the junction box. I didn't get any data. I then tried connecting the cable into the computers NMEA ground and output terminals, after which none of the networked FFDs were showing any sort of data, though they were powering on. So Now I can see all the labels such as depth, speed, etc with blank screens under the header. Those FFDs appear to be reading from the computers network data terminals, which I did not touch. I am much more involved with software at this point and I have no idea what would be causing the network to stop showing data like this . Does anyone have any suggestions for figuring out what is going on here?

[Notyetsinking]

stuck my multimeter on the network cables and now all the FFDs that seemed to be powered from that cable do not power on....they all have power....did I somehow create a short and blow up the displays?