GP1971F + GP330B NMEA 2000 Connection Gone

[Limu]

Have a GP1971F connected to the Gb330B GPS antenna via a the most basic NMEA 2000 backbone:

drop goes to the 1971 on one tee, power comes in the other tee, antenna connects to one end of backbone (have terminator pin inserted on the antenna end of cable), terminator cap on other end.

Worked fine for the last 2-3 years (about 200 hours). Very light use…

Today: Position alarm sounds when I power the 1971 up. No NMEA devices available to choose from on the 1971 interface menu (where it was previously set to look for position data).

Internal GPS works fine.
Checked power on the bus, all good.
Checked all connections and wiring including on antenna: all dry and in excellent condition.
I watched the NMEA 2000 monitor and don’t see any of the PN output codes That the antenna would transmit (based on the 330b user manual).

I’m pretty sure I have software version 3 on the 1971 (mirroring came online with that version, right)
Searched forums for similar issues. None quite add up. I’m thinking it could be three possibilities:

1) something’s not grounded (?? Not that big of a boat and fiberglass?? No other symptoms);
2) VHF and GPS antenna wires running parallel (and slack coiled and cable tied; why did it work as long as it did?);
3) fried receiver on the gps antenna due to proximity to vhf antenna. I adopted a previous owners mounting options (with a 7000f and gps antenna that worked fine). But I have transmitted VHF maybe 10 times in the last 2-3 years.

Would images help?

Suggestions?

—Mail in antenna for testing?
—I might have spare nmea parts (a tee and terminator) to see if that will change anything (connecting via a drop instead of an end)
The 330b antenna cannot be connected directly to the unit (at least with the cable I have), so cutting out the nmea bus isn’t an option. I don’t have any other devices that use nmea 2000.

 

[Johnny Electron]

Are the grounds from the NMEA 2000 bus and the GP1971F connected to the same grounding point? Is the GPS inside the radar beam or near any other RF source that might cause it to become faulty? (Normally if mounted in the radar or near RF source GPS antennas go bad about the 3 year point due to front end amplifier damage) Are both sets of the power wires of the NMEA 2000 power tee connected to proper power/checked fuses? (many have two sets and if you only power one; only the devices down the one side of the tee receive power)
A photo of the boat showing the GPS mounting in relation to other items might be helpful. Of course you could send the GPS head in for testing if you can't determine anything.

 

[Limu]

Mahalo for the questions—

If I remember correctly, my boat is not running any grounds…not impossible to change, just that it came that way, and when I re-ran all the electrical, I copied it. 18 ft fiberglass recreational boat. 2 outboards. 1 basic vhf radio. 1 car stereo. 1 raymarine AutoHelm. The 1971f with a 1k transducer. I have a spare wire run from the stern where the outboards and battery boxes are, but would need to jump to a grounding surface on the outboards and put a grounding bus in up front.

The GPS antenna is very close to the VHF antenna (less than 1 ft), image below.. I inherited mountings and “just” reinstalled on previous mounts. Of the 200 hours on the water, I think I’ve transmitted on VHF maybe 5 times. If the mere presence alone of the vhf antenna burns the amplifiers, in 200 hours, then this is a possibility. The mounts can be moved…new holes in the hard top I guess.

I will post a drawing of the nmea network below . It only has one power input which’s right next to the tee with the drop to the 1971, and the able from the 330b comes in one the end. The side oppose the power injector has a terminator cap.



View attachment Nema.pdf

 

[Johnny Electron]

Given the information, I suspect the most likely problem is the GPS antenna front end is smoked from the placement. I would recommend pulling the GPS head for testing.

 

[Limu]

I will proceed with that and report back. Thank you!

 

[Limu]

Since I wanted something before the family visits over the holidays, I ordered a used but functional 330B unit off ebay, and installed. No change to issue. bummer? Now I'm back to checking wiring...and while I'm at it, increasing the distance between the GPS and VHF antennas. To be continued...

 

[Johnny Electron]

Thanks for the update but sorry that wasn't the smoking gun. I guess the new one is also not showing on the bus at all? I am with you it sounds like wiring.

 

[Limu]

The gps wire was the issue. Who knows between kids, weather, etc must gotten a good yank or twist at some point. Upwards and onwards.

 

[Johnny Electron]

Glad you found resolution. Great job.