Electrical interference help

[Gone sailing]

I have a clipper depth unit that displays random numbers when my raymarine xp5 autohelm is on auto.
It was all ok upto a week or so ago not sure what has changed!

Today I fitted some ferrit chokes at various strategic points on the wireing with no effect.
I then disconnected all the electric to one of the battery's and ran the depth unit off this so it was completely isolated from everything. I also pulled the coaxial wire from its current route and had hanging through the middle of the boat away from all other wires. I removed the depth sounder head unit away from the other instruments.

Despite it being on its own circuit and the coaxal wire in clear air I still get interference when the auto helm is engaged!

Could the autohelm or depth be faulty? They both work ok independently of each other.
No other instruments are picking up interference.
Is there some kind of suppressor that I can fit?
Not sure what to try now!?
Thanks jim

 

[lw395]

I have a clipper depth unit that displays random numbers when my raymarine xp5 autohelm is on auto.
It was all ok upto a week or so ago not sure what has changed!

Today I fitted some ferrit chokes at various strategic points on the wireing with no effect.
I then disconnected all the electric to one of the battery's and ran the depth unit off this so it was completely isolated from everything. I also pulled the coaxial wire from its current route and had hanging through the middle of the boat away from all other wires. I removed the depth sounder head unit away from the other instruments.

Despite it being on its own circuit and the coaxal wire in clear air I still get interference when the auto helm is engaged!

Could the autohelm or depth be faulty? They both work ok independently of each other.
No other instruments are picking up interference.
Is there some kind of suppressor that I can fit?
Not sure what to try now!?
Thanks jim

Some capacitors across the supply to either unit might help.
Check the connection of the coax to the depth transducer and the conditon of the cable.
Also check the hull is not covered in weed under the transducer, maybe the unit is not getting enough returns and has cranked up its gain, picking up noise?
100nF capacitors alias 0.1uF is generally about the right value to try.

 

[cimo]

........... fitted some ferrit chokes at various strategic points on the wireing with no effect.

strange. From your description, the logical conclusion would be that the autohelm is the source of interferrence.

When you say "autohelm engaged", do you mean when the clutch is engaged or when the autohelm is powered on. (i.e. is the autohelm motor the source of interferrence?) You have verified that the autohelms ferrites are fitted in the correct positions? Other than that, verifiy that all shielded cabling (across both systems) is still well grounded, usually at at one end only.

 

[Gone sailing]

Thanks for your help. I will try some capacitors tomorrow.
It does seem to point to the autohelm. The xps5 has four components the motor arm, computer unit, head unit and compass. I get interference every time the autohelm is in auto mode ie the motor is running. But I also get it sometimes when the motor arm is disconnected and I just press the control buttons on the head unit.
I tried the ferrites at the end and begging of all the main electic cables to the unit also on the motor arm.
I got this message back from Nassa but still waiting to hear back from raymarine.

It sounds like the Autohelm has gone 'noisy' and emitting low frequency RFI. There is a very sensitive receiver in the depth sounder so any low frequency noise present may well be picked up. Have a word with Raymarine and explain it used to be okay.

We can test the depth sounder if you wish but think it most unlikely to be faulty.

 

[LadyInBed]

Probably noise being generated by the AH motor.
Try cleaning the motor brushes, spray on contact cleaner might do a job. Also check / clean all the AH connector contacts as a bad contact can cause noise.

 

[Gone sailing]

I think I have sorted it .
I went to the boat today armed with contact cleaner and a couple of capacitors but they made no difference.
I had checked the connections before and they looked sound with soldered ends. I gave them another look today and for some reason I pealed back the wire a bit. The wire from the motor arm to the plug was completely black / corroded.
I have now soldered on a new wire and the interference seems to have stopped. Yippee.
Thanks for your input
Jim

 

[cimo]

nice one. beer o clock.