Depth Sounder and HDMI interference

[OlygirlNav]

We have been investigating why the depth sounder was intermittent on our boat. R29 2020 model
After going through 3 different locations for depth sounder, 4 different depth sounders and a new chart plotter I started looking at the connections.
The symptom was the depth sounder would work sometimes but would fail in shallow water, deep water, slow speed, fast speed, calm water or rough water. The sonar screen would start to stutter and then freeze. Resetting the depth xmit off/on would sometimes work, not always. Power cycling the Chart plotter would work sometimes not always.
Also had issues connecting iPad to boat wi-fi.
Reset depth transducer to factor defaults.
Went through, one at a time, disconnecting the following while sitting at the dock:
NEMA backbone - depth still failed within 1 min
Turned off auto guidance - depth failed within 3 min
Removed Garmin Map and Active Captain Memory cards - depth failed within 3 min
Turned OFF CHIRP - depth failed within 6 min
Removed "Network" Cable - depth quick fail less than 1 min
Removed the "HDMI" cable from chart plotter "HDMI Out" - ran at the dock for 10+ min
Added in the items removed one at a time without HDMI connection and no issue for 10+ min
Went out for 5 days with four different legs of the cruise and depth sounder worked under all water conditions and at all depths
Has anyone else experienced this or similar issue and how did you resolve?
Working on why the "HDMI Out" cable would cause the depth to fail, ideas welcome?

 

[blifland]

1. the cable may have a short in it.
2. possibly a device in the system is not properly grounded so #3 below happens.
3. the cable is not very well shielded and is acting as an antenna; leaking spurious RF (radio frequency) signals/energy.
Try putting the cable back in and turn on your devices and instruments. Place the antenna of a portable radio that is on AM band (or your handheld VHF) near or on the cable and see if you get noise. If so - try a better shielded cable.
Not all HDMI cables are of good and useful quality.

 

[trailertrawlerkismet]

Is your depth sounder an Airmar P79, attached to the hull interior? If so it holds 2.4 oz of fluid, does it have fluid? Also the f it’s the P79 there is supposed to be an O-ring slid up onto the transducer that attaches into the cup reservoir. No O-ring and the fluid will leak out over time and you loose your depth reading. You may not have this particular sounder so disregard if so.

Jim F

 

[OlygirlNav]

Thank you for input.

First thing I did was to get the small ratchet required to check the fluid level on the transducer. The fluid and o-ring were good.

I will get a new HDMI cable and see if that addresses the ground shield issue.

 

[iggy]

I would try to keep the two cables apart as much as possible. If that failed than i would replace the HDMI cable first and than the transducer cable. The shielding in the cable may not be working right.

 

[HookedUp]

From years of working on strange problems on computers, I'd suggest a few simple options: Make sure your HDMI cable is not running parallel to your transducer cable. If it is, introduce some curves so they are not parallel for a long run. You might also try adding a ferrite to either of the cables, but I'd try to get one for the HDMI first.

Hopefully, it's just a noisy HDMI cable and replacing will resolve it, but as I was building my house I put in lots of ferrites to insure a noisy cable wouldn't induce problems on a nearby cable (phone lines, ethernet and coax). It was impossible to avoid long parallel runs, so ferrites were used.

 

[OlygirlNav]

First suggestion for a ferrite bead on the cable is non-starter. Ferrite beads are good for power signals, not shielded twisted pairs. Good thought.
Second suggestion was replacing cable which Ranger Tug did today going directly from Garmin chartplotter to the large TV in the back and depth sounder ran just fine while at the dock. Ranger Tug tried replacing one of the "unions" on the routed path still had failing depth.
Conclusion is that there is something in the routing of the HDMI cable, splitter, or unions that is causing the failure.
Since we do not have a stern helm station having chartplotter connected via HDMI is not "hard" requirement. IPad would work just fine to see the screen.
For now will leave HDMI to chartplotter disconnected.

Will try one last experiment when underway with the direct wiring and see if continues to show depth. If yes, then suspect, splitter or another union.

Thank you everyone for your suggestions and ideas.

 

[OlygirlNav]

Update on the Depth Sounder
Just returned from a 5 day cruise where our depth sounder worked the entire time. All speeds and depths! Yeah.
The Fix: Garmin Field Rep determined that the Chart Plotter Chassis ground was not connected so he made a simple connection from the chassis ground to boat ground on the fuse block in the head.

So the HDMI cable was a clue that there was an issue with the ground. Hookedup was on the right track, thank-you. I have not yet checked the depth with the HDMI cable connected underway. That is still to do just not on a day with heavy fog!

 

[MarcoArias]

HI!

Hope you are doing well! How did the Kingston trip go for you two? As for the grounding issue, I am forwarding the information back to the factory now for feedback to ensure that the unit is properly grounded on each boat. Happy boating and hope to see you soon!

Thanks!

 

[OlygirlNav]

Thank-you Marcus for taking the "fix" back to the factory. Not every boat will have this issue. Does not hurt to take preventive steps!
It was so nice to enter a new harbor and have depth to ensure water level was good.
Kingston was fun. Not a lot open due to Covid-19 but a nice change for us and fun to visit places we went in our R23.