Fishfinder Noise Filter

I have a Lowrance Elite 4 dsi fishfiinder that just went blank. Seems the noise filter in the wiring from the battery is not passing battery voltage to the fish finder. I removed the filter & hooked the battery up once again & now fish finder powers up. Haven't been out on the water to test it out yet, but is this noise filter needed? The only other electrical device I have on board is the Evolve 2 motor.

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PA 14; 2012
Cape Fear River - NC

Simple/cheap "Noise filters" usually comprise a higher-perm-lossy ferrite, toroidal core that the cable is passed through.
It makes no sense to me that removing the filter changed the operation of the fish finder. Maybe a bad electrical connection or the unit is flaky?
Usually these filters are needed to trap/absorb higher frequency noise that other on-board sources generate.....like a electric motor control switching circuit or ignition noise from a gas engine, etc.
Since you have the Evolve 2 motor, if anything the filter is redundant or not needed IF the Lowrance operation is normal after the filter has been removed.

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Dr.SteelheadCatcher
Warrenton, OR

Thanks Dr.
When I meggarred the two wires on the noise filter, the black had continuity & the red was open circuited. That's why I removed it & hooked it up without.

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PA 14; 2012
Cape Fear River - NC

Does anyone know where a replacement noise filter can be purchased? Can't seem to find a vendor or part number on the Lowrance or Navico websites.

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PA 14; 2012
Cape Fear River - NC

Why don't you cut off the noise filter(if it is permanently attached), solder the wires together and make sure your finder is working. Then use a standard ferrite core noise suppressor. They are pretty much all the same.

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Waterman at Work - Kayak Fishing Photos, Video,Kayak Rigging - Blog

If your unit is still under warranty, I would contact Lowrance about the problem.

It sounds to me that the "noise filter" is a shielded box with an input and output cable???
If this is the case, the filter is a pi filter that has both an inductor(s) and capacitor(s) inside the box and is more than a single turn, of the cable, passing through the do-nut hole in a ferrite core.

It could be the fish finder has an intermittent problem....cable, connector, high resistance on connector pins????

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Dr.SteelheadCatcher
Warrenton, OR

Thanks Dr. for your help.

It looks like this:

https://www.flickr.com/photos/93566836@N02/16869785227/

Will try the PA today without the filter.

[url][URL=http://s1249.photobucket.com/user/xxprotegexx/media/fish%20finder%20how%20to/IMG_20140102_171459_055.jpg.html][/url]/url]

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PA 14; 2012
Cape Fear River - NC

The filter is a "typical" ferrite core where the cable passes through the hole in the core.
If your fish finder works without the filter, then the wire through the filter has a bad connector termination or has a broken/open wire.
Easy to check each wire for continuity by using an ohm meter.

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Dr.SteelheadCatcher
Warrenton, OR

Thx Doc....went out today w/o the noise filter attached...did not see any issue w/ the fishfinder/chartplotter/sonar instrument...even w/ the Torqeedo motor going full blast.

Guess I will leave it as it is.

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PA 14; 2012
Cape Fear River - NC