Re: [Amel] Isolated or non Isolated DC to DC Convertor

Herbert Lackner

thanks danny. is there a danger of eletrolytic corrosion when it is used as a HF grounding? I thought that HF would not create these problems. Why would you not connect the SSB ground to the rudder?

SN #120, Kali Mera, Croatia

Am 29.11.2013 20:40, schrieb Yvonne:

Hi Herbert,those thick green and yellow cables on the rudder stock are
the end of the bonding circuit that connects all metal objects in the
boat including the cast iron keel and then to the zink anodes on the
rudder. not a great place for the SSB grounding.
SM299 OceaPearl
Sent from my iPad

On 30/11/2013, at 6:21 am, "Herbert Lackner" < [10]>

We will install a Kenwood 480HX SSB with an MFJ 993BRT automatic
antenna tuner on our SN #120. We do not have a HF ground plate (I
think that was an only an option for the SN). To ground the antenna
Tuner I planned to connect it to the rudder shaft where the thick
yellow/green cables are connected (I assume they are for the VHF

is that ok? (do not want to have a Swiss cheese rudder shaft J )

Thanks, Herbert

SN #120 Kali Mera, Sukosan

VON: [2]
[ [3]] IM AUFTRAG VON Joel F
GESENDET: Freitag, 29. November 2013 17:16
AN: [4]
BETREFF: RE: [Amel] Isolated or non Isolated DC to DC Convertor

All Amel boats since at least as far back as the Meltem in the
1970’s has a floating/full earth return 12 and/or 24 volt direct
current system. Simply, this means all DC power comes out of the
battery, to the device that needs the power, AND THEN RETURN
possibilities of corrosion and keeps noisy things like fans and
fridge motors from ‘talking’ to your radio, stereo and so forth.
It is extremely important to never corrupt this system as, depending
on how much power has been corrupted, you can suffer serious
problems with electrolysis and feedback.

All Amel’s that had a ICOM SSB installed at the shipyard came with
a special ICOM 24-12 volt transformer/converter with an isolated
negative to accommodate the floating/full earth return. If you
provided your own equipment for them to install, they always
insisted on the special isolated negative transformer and would not
install transformers that were not compliant with this. SSB’s
require a healthy amount of power that can cause trouble if not
integrated into the DC system correctly.

If your Amel has been modified by those unknowing of the type of DC
system it has, change it back to the way God and Captain Amel ( and
Jacques Carteau! ) conceived it.

If an electrician or electronics installer comes to your boat, be
sure to ask him if he is familiar with a floating DC systems. His
answer should be in the affirmative with a compliment that this is
the best way to power DC gear. If he says “no”, “that’s
stupid”, or “Whuzzat”, send him away. Trust me, you don’t
want to screw around with this. I sold a SM 53 boat where the rudder
shaft was Swiss cheese because of an improper SSB install. When we
dropped the rudder to replace it, I bent the shaft in half with my
bare hands. They guy who bought this boat still owns it, I believe,
and I invite you to chime in here. He spent $3500 to repair the
wiring and more to replace the rudder shaft here in Fort Lauderdale.
Amel was a big help with technical assistance but Carteau admonished
me to not screw around with the DC electrical system even though it
wasn’t I who ever messed with any DC system on an Amel.





Mailing Address: 401 East Las Olas Boulevard #130-126

Fort Lauderdale, Florida 33301

Phone: (954) 462-5869 Cell: (954) 812-2485

Email: [5]

FROM: [6]
SENT: Friday, November 29, 2013 10:27 AM
TO: [8]
SUBJECT: Re: [Amel] Isolated or non Isolated DC to DC Convertor

Hi. Under the navigation station the doors on the right side have 12
V power supplies that should be your source for 12 V coming off the
24 bank. I believe the brand name is sailor.

In the ass locker there should be a copper foil for grounding the
A140 tuner.


Richard Piller

Cell 603 767 5330

On Nov 29, 2013, at 8:27, < [9]> wrote:

Some advise is needed with respect to the replacement of the
factory installed 24VDC to 12VDC DC to DC Convertor.

We are about to install our Icom M802/AT140 SSB Radio.

The existing 12VDC wiring system is quite mess and includes a
separate 12VDC battery that was used for the previous SSB

I have heard that an Isolated ground DC to DC convertor should be
used. These are used in systems that are ether positive ground or
with floating ground systems.

I am pretty sure that our vessel (SM#196) does not have a positive
ground system.

Did Amel built their boats with a floating ground?

What does this mean with respect to installing a DC to DC

What are the ramifications for using a non isolated DC to DC

Any help understanding this is much appreciated.


SV Libby SM#196

San Diego


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