Autohelm ST50 Depth - cable wiring help please

[UncleAlbert]

Having lost patience with the depth indicator constantly failing to provide data I have inspected the cable and determined that the plug was probably the most likely culprit, closely followed by what appeared to be damage (superficial) to the cabling, which had been pinched behind some cabin trim at some time. So I have removed the socket on the wire which disappears into the back of the display instrument, (two wires Yellow and Red insulated and foil screening). Futhermore I tried to remove the moulded 2 pin plug off the Airmar Transducer cable so as to determine which cable goes to which pin. In this I have been unsuccessfull so now do not know which of the two insulated wires (Blue and Black) and what to do with the bare multistrand part and foil shielding goes to which of teh red or yellow ones.

Having searched though many previous threads going back to 2008/9 there seems to be a wealth of info on this cabling subject, but not exactly what I am looking for, that being :-

the Yellow wire joins to the ?????
the Red wire joins to the ?????

I am planning to remove about 5 feet of the cable, to ensure the possibly damaged bit is taken out of the equation, and will be using solder heat shrink joiners for the connection.

Hope someone can put me out of my misery on this.

And finally is there a way to test the outcome without putting the boat back in the water. It has been written that transducers do not like working in air and other comments have suggested that it makes no differences other than the depth indicated is wrong due to air water density differences. I just need to get a any depth shown on the diplay before I resign myself to either a new 'ducer or a whole new set up with more holes in the boat.

Any 'Janet and John' guidance would be appreciated.

Uncle Albert
Now with even less hair than before

 

[tillergirl]

On the Tridata, the Blue is + depth, black is - depth and the bare is the shield. Red is + power, Screen is - power. On stand alone instruments you do not use the yellow I believe. By the way, I don't think you should shorten the transducer cable - something about it being matched to the transducer and affecting the calculations.

 

[UncleAlbert]

Many thanks Tillergirl.

So the Red wire joins to the Blue one and the yellow (which come to think of it is a bit of sleeving on bare wire) joins to the bare wire which is also in contact with the foil screening stuff.

As you can see my electrical no-how is marginal to say the least (best not to mention blowing up a brand new alternator by missconnecting the ground to live, I really am quite dangerous when involved with the invisible elektrickery stuff)

In regards to the cutting of the cable .................... too late, its done already.

Why do I feel like a new Airmar is likel??????!!!!!!!

 

[Jaramaz]

to cut or not

"In regards to the cutting of the cable .................... too late, its done already."

Well, there are two issues to consider, having cutted the cable:
1) do not make the total cable shorter then the original. Some echo sounders rely on given cable lengths. (this is often discussed at various forums, fact is most echo sounder manufacturers recommend to stick to original length.)
2) see to that the contacts between the new cable and the old old is as perfect as possible. They should be both preassured and soldered to garantuee good connection without any reflections (used frequency on the cable is usually in the range of 200 - 400 kHz, far far above DC).

Good luck!

/J

 

[pvb]

And finally is there a way to test the outcome without putting the boat back in the water. It has been written that transducers do not like working in air and other comments have suggested that it makes no differences other than the depth indicated is wrong due to air water density differences. I just need to get a any depth shown on the diplay before I resign myself to either a new 'ducer or a whole new set up with more holes in the boat.
(

You need a piece of plastic drainpipe about a metre long, with one end closed off. Put the open end of the pipe over the depth transducer, with the pipe perpendicular to the flat face of the transducer. The depth display should read about 5 metres (because the speed of sound in air is about a fifth of the speed in seawater).