can you cut/mend Autohelm cable - they say No!

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alex23299

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I've damaged the cable from my ST40 speed instrument - it isn't cut but the insulation's thorugh and some of the filaments are broken. I can get the speedo to work temporatily if I fiddle with it, but it won't stabilise. The advice I'm getting is that I have to replace the whole damn thing, cable AND impeller. Any advice please?
 
Shouldn't really be a problem to repair - I guess the Autohelm people are being conservative. I've stuck my wind instrument cable together so many times now there's not much left.
I guess the cable or the main part of it will be a screened lead (like a co-ax) and that's the only real problem. You need to reinstate the screen as best you can around the outside of the core or cores. The screen protects the cores from stray electrical pulses you might get from the engine or elsewhere and if you leave a gaping gap in the screen you might find spurious pulses get in giving you errors in your readings.
Having said that it isn;t difficult to do a good job - I recommend soldering and heatshrinking.
Another alternative is to find a mil-style multi-way plug and socket which includes a co-ax pin (have a look in RS then buy on Ebay) though the cost might be high.
When all's said and done you have nothing to lose by trying, and I agree that Raymarine are being excessive if they want you to buy a new transducer and cable.
 
I'd second that, there should be no problem with a ST40 Speed cable, it's only counting pulses from the impeller. It would be a different story for the depth (echo sounder) where the cable carriers the 200kHz (or there abouts) pules and the very low voltage echo signals and any break, damage or repair will reduce the signal signficantly.
Even a standard connect block would work as a tempory fix for the speed unit.
 
If it only has 'some filaments broken' that shouldnt have stopped it working. One strand intact should keep it working . Something else is broken.

If it stopped working when you damaged the cable, you might have broken the insulated core of the cable as well.

Cut out the damaged bit and you will probably remove that break as well. Then it doesnt matter too much how you join it provided water doesnt get in.

If the strands dont look shiny, especially if they are black, water has already crept in. It is probably less hassle to replace it in that case.
 
if you remove the outer cable insulation for about two inches either side of the damage. Then sort out the conductors that have been damaged from the good ones, then one by one gently try and pull the damaged ones apart. If they part with just the insulation holding then just strip back solder together and insulate.
When this has been done for all the affected wires then reinsulate the outer again.

Steve
 
Just to put the manufacturer's response in context, the cable is part of the transducer assembly, which is manufactured by Airmar. Raymarine cannot advise you on how to fix it! A visit to the airmar website technical section will confirm the wiring of your transducer and give you an indication of how to set about a repair.
Rob.
 
If you buy a replacement transducer from Airmar it will arrive with 5 conductors and a junction box, with instructions to cut the old cable and connect close to the instrument end plug.
 
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