Hi Joe and thanks for your input. Some answers below. Aries 1990 C&C 34+ New London, CT
> On Oct 3, 2016, at 9:11 AM, Della Barba, Joe via CnC-List > <cnc-list@cnc-list.com> wrote: > > Some things to try: > 1. Run the plotter off its own battery. Little 6 ah AGM batteries are > cheap enough if you don’t have a spare battery sitting around. Given the intermittent nature of the problem, this would be challenging to do long enough to be definitive. I am also not sure it will identify the source of the problem since it appears to be the power (see below). > 2. Put a scope on the DC bus to see what, if any, AC/noise is on the > line. Include an engine start with this. I don’t have a scope and have not used one. What kind of device would you do this with? > 3. Disconnect the NMEA interconnection and see what happens. As I said, when this happened last week, the NMEA input was disconnected from the chart plotter, so this seems to be coming from the power connection. What is frustrating is that yesterday, I started the engine twice, once before and once after the race, and the chart plotter behaved perfectly and never beeped once. Nothing was obviously different?????? > 4. Check the NMEA connection for configuration. Does the plotter send > and receive data or just send? No need to have the NMEA input line connected > if there is no data headed that way. > 5. Put a laptop on the NMEA connection or run the diagnostic window on > the plotter, if it has one, and read the raw NMEA stream to see if it is > getting some odd data or any data at all if it should not be. > 6. Put ferrites on all incoming wiring. > 7. Check for ground loops and NMEA isolation* > * > This one is a bit tricky. First off, make sure the power supply and ground > connections are at exactly the same place as your other electronics. Ground > loops are bit complicated to explain and hard to find, but the short version > is this step will eliminate some of them. Second is check with the > manufacturer to see if your plotter NMEA connections are true marine standard > opto-isolated. It is very possible to use direct wiring to NMEA data and not > isolate it, my laptop/plotter does just that, but optical isolation prevents > various stray voltage and ground issues from messing up the data. Equipment > is fairly resilient now, but back in the day an engine start could generate > noise that would totally screw up electronics. Even now I will start an > airplane with all radios and nav equipment off and then turn it on. I once > was delivering an airplane that had a screwy alternator I had to switch off > to use the radios and nav gear and then switch back on when the battery got > low. > BTW – my boat is wired so the engine start battery is usually separate at > engine start and has no effect at all on the electronics. They don’t combine > until charging voltage is present for a few minutes. Is yours like that? > Joe > Coquina > C&C 35 MK I >
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