Sonar interference from Balmar reg

[BigAl.NZ]

I am after some advice on how to track down a fault on my raymarine realvision RV200 transducers that basically looks like noise (see picture) when viewed on a Raymarine Axiom Pro 9". The issue seems to be worst in sonar/fish finder mode - not so apparent in side vision or down vision.

Here is the background and what I have done so far:

The noise is present whenever the key is switch to the ACC position, regardless of whether or not the engine is running - although it is worse when the engine is running, and seems worse in deeper water (20m+).

The installation is on a fiberglass yacht. We have two battery banks (start and house) and two alternators (start and house). The ground on the boat is the engine.

So when the key is switch to ACC the noise is present. Only 3 things are connected to ACC, engine alarms, panel lights and power to a Balmar MC612 regulator (for house alt). By disconnecting each of these wires one at a time I have isolated the issue to being caused by the balmar regualtor.

I have also removed the cable from the sonar to plotter and re-routed it away from all other cables and alternator. That made no difference whatsoever so I think this is an electrical issue more than a EMI issue.

A few other folks have suggested to check ground connections for both the sonar and the Balmar reg. I have checked the ground for the Balmar reg and it runs to the negative post of the alternator - there is good continuity without any resistance between them. There is also good continutity from the negative post of the alternator to the engine body.

So this leaves me to look at the ground for the sonar - which is via the chart plotter itself.

When the plotter was installed the ground and batt negative wires were joined and both go to the negative busbar. I also note that the body of the chart plotter has a external ground connection which the manual describes as option, and I presume is a seperate ground just for the case of the plotter?

Beyond these steps - I am unsure what to try next?

The plotter has been installed for a few years and been working well up until recently. Note the bottom picture was with the motor off - you can still see the noise - but it gets considerably worse with motor on - as you can see from top pictures.

[C420sailor]

Not Raymarine, but the Garmin GPSMAP sonar/chartplotter installation guides explain that the additional chartplotter ground should be connected to a 'water ground' if interference is detected.

I'd run a test ground to a good water ground and see if it clears up.

[George_SD]

Make sure the sonar cable runs far from the engine. Mine came with filters that can be attached to the cable.

Running Axiom 7 with in-hull transducer

[BigAl.NZ]

Originally Posted by George_SD

Make sure the sonar cable runs far from the engine. Mine came with filters that can be attached to the cable.

Running Axiom 7 with in-hull transducer

Yes when I temporarily rerouted the cable it was far from the engine.

Since I have a isolated earth (engine) ground - I was thinking of temporarily running a seperate ground wire for alt reg and for chart plotter directly to engine ground (instead of via batt when then goes to engine).

Would this do any harm?

[George_SD]

Sorry, no idea if that's ok or not.

Sonar is a fairly simple device. My chart plotter has pos and neg wires from breakers/bus, then sonar is plugged into the plotter.

Because you are saying that the issue is present even when engine and ACC is off, i would look elsewhere. Could be corroding connections, maybe breaker going bad, or something else. Did you try to feed it power from another breaker or source? What if you feed it directly from the 12v battery? I would try and see if the noise is still present at all. That will at least tell you if the issue is with the sonar/plotter combo or elsewhere in the electrical chain.

[BigAl.NZ]

Originally Posted by George_SD

Sorry, no idea if that's ok or not.

Sonar is a fairly simple device. My chart plotter has pos and neg wires from breakers/bus, then sonar is plugged into the plotter.

Because you are saying that the issue is present even when engine and ACC is off, i would look elsewhere. Could be corroding connections, maybe breaker going bad, or something else. Did you try to feed it power from another breaker or source? What if you feed it directly from the 12v battery? I would try and see if the noise is still present at all. That will at least tell you if the issue is with the sonar/plotter combo or elsewhere in the electrical chain.

The issue is present whenever ACC is on.