Sounder not working with the engien on - (again - sorry)

[webcraft]

Ever since we fitted outr new Beta the depth sounder (NASA Target) has given random depths under engine.

Symptoms:

At medium revs: - Only gives an accurate reading at depths under 3 - 4 metres

At tickover: - Generally gives reasonable results at depths under 10m

Under sail: Accurate at all times up to 50m

Today I fitted a ferrite ring on the big red wire coming out of the top of the alternator, but it seems to have made very little if any difference. Should I fit more ferrite rings elsewhere, and if so where?

All suggestions gratefully received . . .

- W

 

[machurley22]

[ QUOTE ]
All suggestions gratefully received . . .

[/ QUOTE ]
Except, presumably, from DaveS and myself since you have studiously ignored ours for the last two years. /forums/images/graemlins/grin.gif

 

[webcraft]

Refresh my memory - I believe you mentioned ferrite rings. Well, I've tried that and it isn't working . . .

And anyway I've forgotten and you haven't even bothered to put a link to your old posts so how do I know I've been ignoring you?

You will be moaning that I've spelt engien wrong next . . .

 

[machurley22]

Lots of ferrite rings is the answer. I seem to remember describing fitting one and then going up to three but perhaps I just imagined the whole conversation and Dave's similar advice.

Try five. Even you can afford a tenner for such an off-the-wall experiment.

 

[Fr J Hackett]

Hi Nick
How are you fitting the ferrite? It needs several passes of the cable through the ring, I doubt that the main alternator cable can do this. If you can find a clamp on type try RS then it might do the trick but try fitting the ferrites to the cables of the depth sounder and display since these may be picking up the RF.

 

[FullCircle]

http://www.markpalmer.fsnet.co.uk/radio-pictures/fig8.bmp

Like this?


Nick, is it possible to route the wiring away from the main run? The RF safe distance is quite small, but it sounds like you may have some insulation breaking down in the main loom (current carriers). Is it old cable?
Did this come on gradually over a period, or has it always been there?
Does the radio (not the VHF) hiss or pulse when you have the engine on? Does it change with engine revs?

Have you tried to see what effect there is when, for instance:

You are using ALL circuits switched on?
Battery at full charge when alternator does not see a big load?

Usually you would not need a lot of ferrites, I havent on any of my previous boats, just one on the VHF normally, and your alternator will be outputting to similar circuit layouts to mine.

The ferrites are a good idea, but my guess is you are sticking plastering another root cause.

 

[webcraft]

I've put a big clamp-on type on the main alternator cable.

This problem has existed from the moment the new engine was fired up. All the wiring from the engine / alternator and the main loom from the engine is brand new. The echo sounder worked fine with the old alternator that was fitted to the Volvo.

No interference problems at all with the VHF.

I will trace the witing to the sounder and see if I can re-route it - but the cable form teh transducer has to be a fixed length doesn't it? Its it the cable from the transducer that should have the ferrite rings or the power cable to the instrument or both?

Where should I get ferrite rings from, what should they look like and what diameter should I get?

- W

 

[FullCircle]

Nick,
the transducer should have the proscribed length, but nothing to stop you bunching it up at the transducer end with a couple of cable ties.

The ferrites should be put at the noisy end of the problem, at the power cable, not the transducer, as that is not the radiator of the noise.

available at cheapo cost here

There is setup/use and FAQ links on that page.

So, we have a set time point for the start of the issue, so therefore logic says that it must be due to something that has changed at that point.

Could I suggest you try the echo sounder with a separate battery source, i.e unconnected to the boat wiring, and then run

I would suggest you get into Problem Solving techniques here, so I would list out all of the parameters of:

What it is
======

i.e 3-4m inaccuracy at X revs



and, just as importantly

What it is not
========

i.e engine wiring and routing that existed previous to new engine.
wiring from the fuse board distribution


That way you will be able to eliminate by logic or investigation all of the 'is' and 'is not' parameters..

Whatever is left, however unlikely, is the root cause.