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Jon Wright

Autopilot Upgrade - ST to STng power

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Hi all,

Due to an unexpected illness in the family I'm travelling back to the UK in a few days for a flying visit. The only bright side is that I could use the opportunity to buy a much needed autopilot upgrade while I am there for a lot cheaper than in Grenada.

So I'm trying to work out the technical setup of how it would work. Could I ask someone to sanity check this before I spend a fortune on the wrong gear. It would be greatly appreciated.

To make life easier I have linked to two diagrams, the first is my current setup. I added an AIS last year and with it a seatalk to Seatalk NG converter. This setup works OK - no obvious problems in the last year. The second diagram is what I am proposing to do with a new autopilot - all new items are marked in yellow.

Current setup (working OK):
NB. the STng bus is not powered using the supplied 12v input cable. I guess it is getting power from the AIS or from the ST1 side?

New setup:
My main concerns here is how the whole network is powered. Do I need to buy a lot more St to STng converters for all my old gear and drop the power from the ST network completely?

I'm interested in knowing both what is 'correct and recommended' and what will work. So far I've had no help from Raymarine official channels.


3 Replies

  • Hi Jon, I don't have solid answers but it's good that you've made before and after diagrams.

    I'm confused, though, about how you're powering the ST-to-STng converter now and how that will change in new setup. The manual states:

    "Converter power supply
    The converter takes its power from the SeaTalkng bus and provides power to devices on the SeaTalk spur.
    Power must not be connected into the SeaTalk spur. To be certain, disconnect any existing separate power connection at the SeaTalk devices on the spur."

  • Hi Ben,

    Thanks for the reply. Yes, the manual does state that but for the last year it has been working with several 12v sources on the ST1 side:

    3x Course Computer 12V inputs, one from each of the two ST ports on the CC and an additional one which I've put on the 'bridge' as I was seeing low voltage problems on those instruments.

    On the STng side I don't have any power directly into the STng converter. The AIS 650 does have power going into it but I don't know if that is given back to the STng network?

    The above seems to work for me.

  • Hi Ben,

    I managed to get hold of a helpful chap at Raymarine technical department in the UK. He explained the following which maybe of interest to you, or anyone else reading this thread.

    In my current system:

    The ST1 network is being powered through the ST1 connections on the course computer. The STng network is being powered through the cable which connects the converter to the ST1 network. This is working OK because there are only a few devices on the STng network (the AIS and the MDF - both of which have their own power supply). This is not following the guidelines but he said that it won't cause any problems if it is working now.

    In my planned future system:

    1)Provide power to the STng network via the dedicated power cable ideally into the 'middle' of the network - in my case into the STng Converter will do.

    2)Cut the power wire (red) in the cable which connects the Converter into the ST1 network - to ensure that power is NOT moving coming from the ST1 network into the STng network.

    3) Power the ST1 network with 12v from anywhere I like - I'll keep it on the autopilot fuse and breaker to keep it 'correct' and simple.

    See the updated diagram - additions marked in Yellow.

    Yes, the two networks will be powered separately and that is OK according to the guy at Raymarine UK.