Minn Kota US2 Interference

There have been a few post on here about the interference issues with the US2 on Minn Kota tm's. I posted about my interference a few months ago and got several ideas. My depth finder is a HB 747C, it was on the boat when I bought it. I have been using lowrances for several years and have had great service out of them. The HB on my boat worked great with the exception of the interference, it made pretty arches:D.

I bought a used HDS5 at a good price recently, before I changed the units out I thought I'd try some things to see if I could help the HB. First I ran a common ground from the tm batteries to the starting battery, No help. Next I tried a ground to the tm in several places, no help. Same with the noise settings, no help. No single thing or combination helped.

I also bought the adapter for the Lowrance to try the US2, I used my Fluke meter to test continuity between the knurled nut on the end of the cable and any of the pins on the other end of the adapter cable for the Lowrance. There was some continuity with two of the pins. On the HB there was none on any pin. My thoughts here was that if there was continunity that a ground to the nut may help. Another thing I noticed was that the Lowrance power cable is shielded, I didn't see any evidence of shielding on the HB cable. Does it make any difference? I don't really know.

I removed the HB and installed the HDS and ran the tm, I saw no evidence of interference at any speed.

Please don't think this a bash on HB, the 747c is a fine unit. I just wanted to try some different things, unfortunately nothing worked, for me any way. You're results may vary : ).

Meter between the US2 metal connector housing and other pins in the HDS connector adapter. The shield is probably tied to some pin. The US2 shield is tied to the TM motor housing, but the us2 ground wire is floating (not referenced to the TM shield). This could be the difference. Check it out.

You have a tin boat or a plastic boat?

I don't know what you mean by some continuity? The is a thermistor inside the US2 for temp. You could be reading it. So what is some equal to in ohms?

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Originally Posted by Cane Pole

I don't know what you mean by some continuity? The is a thermistor inside the US2 for temp. You could be reading it. So what is some equal to in ohms?

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Is a thermistor like a thermocouple if it is it should read a certain amount of ohms to read correct temp

I guess I should've written "there was continuity". I did not check the trollong motor, what I checked was the adapter cables for both depth finders. I was not looking for a certain ohm value, only to see if there was continuity. I apologize if my terminology is not up to snuff. As I mentioned in the orginial post, I wanted to try to work this out before I removed the hb. Don't mind me, please carry on.

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Originally Posted by wilbur

Is a thermistor like a thermocouple if it is it should read a certain amount of ohms to read correct temp

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It is a heat variable resistor, not a thermocouple. The resistance of the sensor changes with temperature.

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Originally Posted by justinp61

I guess I should've written "there was continuity". I did not check the trollong motor, what I checked was the adapter cables for both depth finders. I was not looking for a certain ohm value, only to see if there was continuity. I apologize if my terminology is not up to snuff. As I mentioned in the orginial post, I wanted to try to work this out before I removed the hb. Don't mind me, please carry on.

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Try the ground to the Knurled connector. That connector is tied to the TM housing. I have fixed noise by grounding the TM housing before, but not with V2. Never know.

I also had the noise with the us2 and a humminbird 777 never did get it solved and did everything i could think of, guess just some of the humminbirds have a problem not all of them, might be a cold joint in the unit or the us2 may not like some of the humminbirds. anyway if you decide to keep trouble shooting and you find an answer let us know please.

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Originally Posted by beagle man

I also had the noise with the us2 and a humminbird 777 never did get it solved and did everything i could think of, guess just some of the humminbirds have a problem not all of them, might be a cold joint in the unit or the us2 may not like some of the humminbirds. anyway if you decide to keep trouble shooting and you find an answer let us know please.

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So true with all makes and models. We need an album where folks can post "noise fixes" or related links. Noise is always a big issue with all types of sonars. None are immune.

One time I had an interference problem between D/F and T/M. I cured it by running a separate battery ground wire down the outside of the composite T/M shaft and screwed it to the motor housing. Might have been something to do with the composite shaft of the MinnKota T/M.

You would think MinKota would of did that and had a wire run through the shaft connected to the neg. power cable.

I didn't try a wire to the motor, might try that while the wires are still out.