Seatalk depth problem. Voltage?

[Tim.Wills]

Hi all. I'm.new to the forum - so much great info! Thanks. My 16 meter classic wooden sailing boat has old but functional raymarime nav instruments, including a ST 30 depth, networked to a ST 7000 autohelm. When the boat is idle ( no charger or engine running) everything works fine, as always,but recently, when either the engine is running or charger connected ( either from shore or solar) the reading for depth jumps very high. .Everything else is unaffected. It seems to coincide with voltage increases at the batteries take a charge. I know it's reading correctly when no charging, as I k now the depth in my marina. Any ideas please?

 

[AngusMcDoon]

Electromagnetic interference is a possibility. Depth sounders are susceptible to this. What engine and charging kit do you have?

 

[Tim.Wills]

The engine is a 4800cc diesel from the 1970's. Super reliable four cylinder with virtually no electronics ( not even glow plugs) It's the same engine out into JCB diggers back in the day,but mariinized from new. Charging is through a hybrid solar charger/ converter. Nothing changed other than the display reading. It seems now that the higher the voltage, the higher the depth reading . Do these head units have a voltage regulation method on the circuit board? I was considering trying a voltage regulator in line on the pos/ neg of where the seatalk comes out of the course computer,between the course computer and the autohelm . Any advice appreciated.

 

[Tranona]

The ST 30 is a standalone instrument and does not need to be connected to Seatalk. Just wire it up to a fused supply from the 12v DC distribution board.

 

[Tim.Wills]

The ST 30 is a standalone instrument and does not need to be connected to Seatalk. Just wire it up to a fused supply from the 12v DC distribution board.

Thanks. It shares log data with the plotter etc ( it's a tridata) but I will try your suggestion direct to a stand alone battery to identify if the wider wiring is a problem. Thanks for the suggestion.

 

[Alex_Blackwood]

Electromagnetic interference is a possibility. Depth sounders are susceptible to this. What engine and charging kit do you have?

Would be my first thought! Have you added or changed any kit or wiring routes etc.

 

[AngusMcDoon]

Would be my first thought! Have you added or changed any kit or wiring routes etc.

As the engine is 50 years old perhaps the alternator has a now non-functioning suppression capacitor.

 

[AngusMcDoon]

Do these head units have a voltage regulation method on the circuit board?

Yes. The supply is nominally 12V but the electronics will run on 5V or 3.3V.

 

[Tranona]

Thanks. It shares log data with the plotter etc ( it's a tridata) but I will try your suggestion direct to a stand alone battery to identify if the wider wiring is a problem. Thanks for the suggestion.

Sorry - I may have mislead you. From what you say it is NOT an ST30 which is the basic cheapo Raymarine range and over 30 years old.

 

[Tim.Wills]

Sorry - I may have mislead you. From what you say it is NOT an ST30 which is the basic cheapo Raymarine range and over 30 years old.

Actually it may be me that misled. It's an old black tridata hard wired with the old type plugs

 

[Alex_Blackwood]

As the engine is 50 years old perhaps the alternator has a now non-functioning suppression capacitor.

OP says "Charging is through a hybrid solar charger/ converter " is that Solar/Mains (I assume) or Solar/ engine? If solar mains and he has the problem with the charger running, without the engine, probably not the alternator. Is the problem only there on the charger with mains on, or does it occur with solar charging alone, or does it only happen if he has engine and mains + solar? I think more info required.

 

[AngusMcDoon]

Actually it may be me that misled. It's an old black tridata hard wired with the old type plugs

This?

 

[michael_w]

I recently cured a fluctuating voltage on my Raymarine gear by remaking the neutral/earth connections. As suggested by two people on Fix it Anarchy.

 

[Alex_Blackwood]

I recently cured a fluctuating voltage on my Raymarine gear by remaking the neutral/earth connections. As suggested by two people on Fix it Anarchy.

They weren't D.C. units then? Do they do a.c.? Sorry!

 

[Tim.Wills]

OP says "Charging is through a hybrid solar charger/ converter " is that Solar/Mains (I assume) or Solar/ engine? If solar mains and he has the problem with the charger running, without the engine, probably not the alternator. Is the problem only there on the charger with mains on, or does it occur with solar charging alone, or does it only happen if he has engine and mains + solar? I think more info required.

Yes, the problem is either when the engine is running or when the solar charger ( or in fact shore charger) are adding to the batteries. When none of the charging methods are connected it reads and responds correctly

 

[Alex_Blackwood]

Yes, the problem is either when the engine is running or when the solar charger ( or in fact shore charger) are adding to the batteries. When none of the charging methods are connected it reads and responds correctly

So, it would seem that the fault is common to whatever charging system is used. I would suspect the original thoughts that it is possibly a.c. Components in the charging system. (Electromagnetic interference). As a first step try Michael W's suggestion and clean up all the connections. You may want to check if the charging leads run alongside the Raymarine cables. Ferrite bushes on the Raymarine cables may help.