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788CI HD DI interference

Posted: Mon Feb 21, 2011 7:58 pm
by cokeman6
Just Installed a new 788CI HD DI on the front of my skeeter 20i and having some interference issues from my minn Kota pro 101. The unit works fine until I engauge the trolling motor and then the screen changes colors and the readings are incorrect. My 798 mounted at the dash works fine.

Please help....

Posted: Tue Feb 22, 2011 3:20 pm
by Humminbird_Greg
Try calling the Humminbird Customer Resource folks about this. I know that the extra shielded HDSi transducer will not help but the trolling motor choke and ferrite coils may.

Do you have this unit connected to anything else like a WeatherSense Fishing Barometer or an InterLink?

Posted: Tue Feb 22, 2011 3:30 pm
by Humminbird_Greg
Got some new info for you here:

When you call the Customer Resource folks you need to see about getting the PC-11 Power Cable to try as it has a built-in choke in it.

If you have the Universal Sonar than check the fuse on the grounding wire in the head of the trolling motor.

How are you powering the 788ci HD DI unit?
From which battery?
Make sure that you have NO CONNECTION between the cranking and trolling motor batteries.

Let us know if you have this unit connected to an InterLink or not.

Posted: Thu Feb 24, 2011 7:14 pm
by jim45498
Greg, does the PC 11 cable with the choke work on the 788ci units?

Humminbird says the PC 11 is for the side image units, is there a difference in power cables?

Posted: Fri Feb 25, 2011 4:26 pm
by Humminbird_Greg
The PC-11 power cable will work for any unit that it can plug into. The differences between it and the PC-10 are:
1. The PC-11 has a built-in RF choke.
2. The PC-11 is made with a heavier gauge wire (18 AWG versus 22AWG in the PC-10).

Did you speak to someone or was this from the web site?

788 CI HD

Posted: Fri Feb 25, 2011 7:10 pm
by cokeman6
Greg, I called HB today and explained the issue and they said that the tranducers (xnt 9 di t) that came with the unit does not have a shielded cable and should be replaced with tranducer xtm 9 si 180 t. Does this sound correct? Is the replacement side imaging and not down imaging?


Posted: Fri Feb 25, 2011 11:18 pm
by SilmarilS
Side Imaging Transducers won't work on DI only units...
They lacks the DI crystals in them!


Posted: Sat Feb 26, 2011 10:11 am
by cokeman6
Maybe this helps....

Setup (independent)

798 - console mount (no issues)
- power connected at the fuse panel
- SI transducer mounted on the transom and high speed thru hull both connected with the Y cable.
- weather sense
- xm satellite weather

788 CI HD - mounted at the trolling motor
- power is connect at the fuse panel
- the trolling motor is a minn Kota maxxima pro 101 with universal sonar 2 (not used)
- XNT-9-DI-T Tranducer mounted on the trolling motor
Works great until I start the trolling motor.

US 2 motors

Posted: Sat Feb 26, 2011 11:27 am
by Wayne P.
Check the fuse on the grounding wire in the motor head. That seems to be one of the common occurrences with those motors when dealing with RF interference.


Posted: Sat Feb 26, 2011 12:44 pm
by cokeman6
Just checked the groud fuse and it's good.


Posted: Mon Feb 28, 2011 12:49 pm
by Humminbird_Greg
No this does not sound right. I think that someone is getting their transducers and units mixed up (which is getting easier and easier to do). The XNT-9-DI-T is the only transducer that will work with your 788ci HD DI unit.

I hate to tell you to call them back but this is the only way that you can get some help. Ask to speak with a Supervisor if you have to. What I have been told is this:
“The first step is to get consumer services to send him a PC 11 with the choke built in. Then need to make sure he has no connection between cranking and trolling motor battery. If it is a universal sonar motor the #1 reason for interference is the fuse in the head of the motor being blown.”


Posted: Sun Mar 13, 2011 9:27 pm
by cokeman6
Ok, I installed the pc11 cable direct to the starting battery with a online 3amp fuse. I tested this week and now the HB works fine except in shallow water when the trolling motor is running.

Any suggestions?

Posted: Sun Mar 20, 2011 9:50 pm
by atlasstone
I'm sure glad to see this topic. I hope there is a resolution here soon. I have been fighting my 788 for about 3 weeks now and though that it might be helpful to post the trouble shooting steps I have used so that others might not have to go through what I have.

Fortunately, I bought the 998 and a high speed transducer at the same time so I have some other equipment to use for troubleshooting. I am also using a Minn Kota Fortrex 101 36v

The following is what I have tried with no success:
  • Running a ground from the cranking battery to the last in line negative on the trolling motor batteries.
    Trolling motor ground to sonar ground at the bow.
    Trolling motor housing to sonar ground
    Various combination of all

    I have chaged th transducer frequencies
    used another battery
    removed all electronics from the cranking battery and tried it again there
    Used a different transducer (high speed sonar)
    used a different unit (the 998)
    Used the interference kit for the sonar power cable
    Used the interference kit for the GPS / Interlink
    Removed the interlink

    Used an RF choke on the transducer
    Use an RF choke on the trolling motor power
    Ran several RF Choke in line on the transducer and the trolling motor
    Used the TMC-1 from humminbird in multiple configurations and even went so far as to connect it directly to the control board on the trolling motor to eliminate the excuse for not getting it close enough to the foot switch.
    Connected power to the boats fused board
    Ran separate lines directly to the cranking battery with the inline 3A fuse
    Was asked to inspect the trolling motor head for the fuse that doesn't exist since it is not a US2

    Minn Kota had me check to see if the skeg was in line and it was
    Checked continuity in the trolling motor housing
    Ran 12Volts through the trolling motor control board and still got interference

    I installed a new Minn Kota Maxxum trolling motor
    Ran a ground from the negative side of the brush plate to the ground that the internal light uses (this was the suggestion from the Minn Kota CSA)

    Pulled all batteries out to remove line discrepancies and provide shorter leads
    Checked and confirmed good power

    Finally, I took it to a friends house and installed it in a new boat using a motor guide trolling motor while swapping the transducers as well and got the same result.

The ONLY thing that worked at all was to bypass the control boar in the trolling motors footswitch and engage the motor directly. I used 36V and 12V and the motor spun just fine and didn't cause any interference. So, from where I stand, thy both work great together if you don't mind losing the ability to raise or reduce your trolling speed and turn the unit on and off.

Anybody heard anything that would help get this resolved? I'd love to hear what someone has done to get it to work correctly.

Posted: Tue Mar 22, 2011 1:26 pm
by Humminbird_Greg
Bypassing the control board worked because it also bypassed the RF generating circuitry it contains. It is this pulse width modulation (PWM) circuitry that is causing the RF signals that are interfering with the units. Part of the problem with RF interference on the Si units is that there is no one solution that works for all boats. What works on one does not always work on another.

My suggestion to both of you is to contact the Humminbird Customer Resource folks and see if they can get someone else to look at your problem (1-800-633-1468) as this is the only way that we can involve our Engineering group.

Posted: Wed Mar 23, 2011 11:53 am
by atlasstone
Thanks for the follow up.

I have been engaged with Humminbird and Minn Kota since I first discovered the issue about 3 weeks ago. Some of the troubleshooting steps that I have performed have been at their request, some at the request of Minn Kota and some of my own in order to try to isolate the problem.

Since my last post, I have installed and tested the new control board that Minn Kota sent and am sad to say that I got the same result.

I am expecting a new 788 from Humminbird today and will be sure to post the results of that test as well.

The 998 that I tested with is an Si unit but the 788 is just 2D and Di, not Si. I'm not sure if that makes a difference, but I thought that it might help to point out the distinction for what I am working with.

I would love to get someone from Engineering involved. I have a fairly extensive ticket logged with Humminbird at this point and would like nothing more than to see it resolved. I was able to get a supervisor on the phone, but will be sure to ask for a resource in Engineering if the new unit does not work.

The unfortunate thing with this is that I only have a short window to work with. I can not send my unit for repair because it would nullify my ability to get my money back from the retailer, and for that I only have 60 days from the time of purchase. If Humminbird is unable to find a resolution, I may be forced to return it and look for something else. I've already spent well over $100 just in additional connectors and wiring just to troubleshoot this. At some point, it becomes cost and time prohibitive to keep trying. I certainly hope we can come up with something.

I appreciate the feedback on bypassing the control board. That was my assumption and the reason that Minn Kota sent the new control board, but it's good to have it confirmed.