I read up on this test. Would be very interested to know the results. Neither my electrician nor mechanic have the tool. What should I expect to spend on one that would do the job? I see cheap ones on Amazon but figure this is probably not the ones I want.
Dff3d Grounding - *UPDATE #3* Interference from Alternators Old and New Persists
- Thread starter ToddF
- Start date
How important is keeping the foil on the individual wires for the 1.5" it looks like in the pic? Mine are trimmed back to the black wire sheathing, in other words, no foil stands out beyond the black cable insulation. Other than that, I think I did it as pictured.
jp498
Furuno Super Fan
For these purposes a cheap ipod style o-scope would be fine. More money gets higher frequencies, more channels, etc...
It's been a while but figured I'd update this thread.
Did a lot of reading up on marine grounds, analysis, and eventually rework on critical parts of my ground, supply, charging and bonding systems. This meant shortening unnecessarily complicated wiring paths, separating the bonding system from the DC negative side (except in 1 spot) , replacing corroded or overused busses, upping wire sizes, lots of new terminals, and double checking my NMEA 2k wiring and drain wires according to Furuno S-1 schematics. Worthwhile work but it didn't fix my dff3d issue.
I've isolated the problem to the engine alternator. I replaced the old alternator with a brand new one, since the other was old and the windings were looking a little rough, and yet the problem remains even with the new unit. I then upgraded the size of the alternator output wiring and added an equal sized ground wire (to main DC neg bus) running together (via cable ties) for as much of the run as possible.
Here's why I'm convinced it's the alternator:
-With DFF3d in Triple beam and Cross Section and depth set very deep, I'm getting the searchlight cone (Cross Section) and hash (Triple Beam) in direct proportion to the RPM on the Yanmar. This happens in neutral as well as in gear so I think I can rule out the spinning shaft.
-When I disconnect the excitation wire form the back of the alternator, the interference goes away! Hooray!
-If I add an 8 AWG wire from the black box (instead of 12 AWG I have) and run it to the engine block or to the common ground bus (running gear, thru hulls, zincs etc) then the problem remains as long as that alternator is producing current. Booo!
So now I can either:
A) Put the excitation wire on a switch where I can deactivate the alternator when using the Dff3d or preferably
B) Add some sort of filtration to the alternator output. I read on here about Filter Capacitors being used for similar motors and other black box sounders. Also, I've also seen a similar product Newmar sells called an Alternator Noise Filter 150A. The Newmar wires up in line to the output, while the Filter Cap seems to wire parallel to the output wire so I'm guessing they work differently
Curious if anybody has any experience with filter capacitors or the Newmar Alternator noise filter. As always, if I'm missing something or on the wrong path please advise.
Did a lot of reading up on marine grounds, analysis, and eventually rework on critical parts of my ground, supply, charging and bonding systems. This meant shortening unnecessarily complicated wiring paths, separating the bonding system from the DC negative side (except in 1 spot) , replacing corroded or overused busses, upping wire sizes, lots of new terminals, and double checking my NMEA 2k wiring and drain wires according to Furuno S-1 schematics. Worthwhile work but it didn't fix my dff3d issue.
I've isolated the problem to the engine alternator. I replaced the old alternator with a brand new one, since the other was old and the windings were looking a little rough, and yet the problem remains even with the new unit. I then upgraded the size of the alternator output wiring and added an equal sized ground wire (to main DC neg bus) running together (via cable ties) for as much of the run as possible.
Here's why I'm convinced it's the alternator:
-With DFF3d in Triple beam and Cross Section and depth set very deep, I'm getting the searchlight cone (Cross Section) and hash (Triple Beam) in direct proportion to the RPM on the Yanmar. This happens in neutral as well as in gear so I think I can rule out the spinning shaft.
-When I disconnect the excitation wire form the back of the alternator, the interference goes away! Hooray!
-If I add an 8 AWG wire from the black box (instead of 12 AWG I have) and run it to the engine block or to the common ground bus (running gear, thru hulls, zincs etc) then the problem remains as long as that alternator is producing current. Booo!
So now I can either:
A) Put the excitation wire on a switch where I can deactivate the alternator when using the Dff3d or preferably
B) Add some sort of filtration to the alternator output. I read on here about Filter Capacitors being used for similar motors and other black box sounders. Also, I've also seen a similar product Newmar sells called an Alternator Noise Filter 150A. The Newmar wires up in line to the output, while the Filter Cap seems to wire parallel to the output wire so I'm guessing they work differently
Curious if anybody has any experience with filter capacitors or the Newmar Alternator noise filter. As always, if I'm missing something or on the wrong path please advise.
Last edited:
Similar threads