If it's rf noise generated by the alternator it may be coming in through your GPS antenna as well as data or power lines. If it is rf noise you should be able to hear it with a small AM radio held nearby (tune to around 1400 KHz). I still think your voltage regulator is suspect. When the battery reaches its maximum charge of approximately 14.2 volts, the regulator will then limit the alternator's output. The battery acts as a buffer so that may be what's causing the problem to sometimes not show with the engine on.. If the engine has been off for a while the battery voltage may fall in the 12's and it may take a while for it to overcharge into the 14's where your chart plotter may start to act erratically again. When you turn off the engine it may take a few minutes for the voltage to drop back into a safe level. You said you are measuring in the 14 volt range with the engine on. If it is above 14.2 that would be suspect. Jerry J7J
-----Original Message----- From: Della Barba, Joe via CnC-List <cnc-list@cnc-list.com> To: 'cnc-list@cnc-list.com' <cnc-list@cnc-list.com> Cc: Della Barba, Joe <joe.della.ba...@ssa.gov> Sent: Mon, Oct 3, 2016 11:08 am Subject: Re: Stus-List Chart plotter problem You could try something like this: http://www.ebay.com/itm/NEWMAR-PC-25-Noise-Filter-Power-Conditioner-25-amps-/231859240381?hash=item35fbe33dbd:g:Zn0AAOSwPc9W0ftz&vxp=mtr Oscilloscope (scope)https://en.wikipedia.org/wiki/Oscilloscope FYI If you know any ham radio operators, they probably know where to find one to borrow. Your plotter also could just be nuts ;) Joe Coquina From: CnC-List [mailto:cnc-list-boun...@cnc-list.com]On Behalf Of David Knecht via CnC-List Sent: Monday, October 03, 2016 09:56 To: CnC CnC discussion list Cc: David Knecht Subject: Re: Stus-List Chart plotter problem 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 _______________________________________________ This list is supported by the generous donations of our members. If you like what we do, please help us pay for our costs by donating. All Contributions are greatly appreciated!
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