Dff3d Grounding - "Torchlight" Electrical Interference in Deep Water

[ToddF]

I started getting some interference in the cross section and history screens of my dff3d but mostly in very deep water (over 400 ft). I read up on the torchlight interference and the most common cause being improperly grounded transducer cable. Here are some pictures of how mine is done. Any feedback?

I did not install this so I'm not 100% sure what's under the tape. It feels like the grounding shield is wrapped around the sheath as guide suggests.
It also seems like the electrical tape is over the grounding shield and then the copper tape is over the vinyl tape (not how the install guide suggests).

Side note: The dff3d isn't on its side like picture suggests. I just rotated it to fit as an attachment

 

[jp498]

Electrical tape is not part of the instructions. I would carefully remove the copper wrap hoping to re-use it. Then remove the tape. The braided shield should be under the yellow tape. If it's not, it should be showing. Wrap the braided shield with the copper wrap, and there should also be some drain wire that can wrap under one of the screws.
The only thing I do different than the instructions is to peel back another 1.5" of insulation as it seems the wires a bit short coming out of the transducer cable.

 

[ToddF]

Thanks!

I typed electrical tape but for all I know that yellow tape could be vinyl tape. I thought they were the same thing.

Good idea. I'll try to preserve that copper tape but will bring some extra just in case

When you say the wires a bit short (peel back 1.5" insulation), I'm assuming your talking about the shielding wire? or maybe all the wires?

Also, when you say there should be some drain wire to wrap around one of the screws, can you elaborate any more? Is the drain wire the same as the shield wire below? Are you making it longer to wrap the screws that tighen the clamp?

 

[Titanic II]

The end game is to have the clamping plate in direct contact with the conductive tape which is in direct contact with the shield wire you wrapped around the sheath.

 

[ToddF]

Thank you. that makes sense aad I appreciate the pictures.

 

[ToddF]

Update:

Pulled back the copper tape and then the vinyl tape. The shield wire was under the yellow vinyl tape with zero contact to copper. I'm surprised the unit worked as well as it did with no contact direct metal to metal contact. Rewrapped the shielding wire properly in copper tape and reconnected. Didn't get a chance to use it but at least now I know its done correctly.....I think!
Thanks

 

[Deep Blue]

ToddF,

This is a common installation mistake. When it comes any sensitive multibeam systems, it's very important to have the transducer cabling properly grounded, as to combat any potential noise issues.

I'm glad that you were able to solve it, good luck out there fishing..!

- Deep Blue