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  #11  
Old 03-04-2021, 05:33 AM
smithflys23 smithflys23 is offline
 
Join Date: Feb 2017
Location: Jupiter
Posts: 220
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Quote:
Originally Posted by cbennet1 View Post
Make sure your intercom jacks are physically isolated from the panel or wherever they are mounted assuming it is conductive. Insulated shoulder washer and flat washers on all jacks.

Lots of other great suggestions already posted. Good luck!
I believe I checked this, but I will look again. Thank you
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  #12  
Old 03-04-2021, 05:36 AM
smithflys23 smithflys23 is offline
 
Join Date: Feb 2017
Location: Jupiter
Posts: 220
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Quote:
Originally Posted by Mich48041 View Post
The strobe negative and positive power wires should be a twisted pair.
Try running the negative strobe wire all of the way to the alternator mounting bracket.
If nothing else solves the problem, try increasing the alternator "B" lead wire size.
These are Aeroled nav/strobes, so there are 3 wires. Power for the nav, power for the strobe, a sync, and a ground.

Iíll have to look into the B lead. I think this connects to the VPX.
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  #13  
Old 03-04-2021, 05:39 AM
smithflys23 smithflys23 is offline
 
Join Date: Feb 2017
Location: Jupiter
Posts: 220
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Quote:
Originally Posted by gasman View Post
I would not consider this a good ground location. The full load of the starter must pass through the battery box bolts.

The forest of tabs should be bolted to the firewall with a passthrough brass bolt. The battery ground should connect to the brass bolt on the engine side. And a ground strap should go from the same bolt, to the engine case.
When I saw how the battery was grounded, I thought this may be an issue.

The forest of tabs is as you describe. Although itís on the panel aft of the actual firewall. Iíll have to see what is involved in running a new ground for the battery.
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  #14  
Old 03-04-2021, 12:23 PM
smithflys23 smithflys23 is offline
 
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Location: Jupiter
Posts: 220
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Before I flew today, I did another quick test.
With the engine running, and the alternator off, the noise disappears. Alternator on, it returns.
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  #15  
Old 03-04-2021, 02:46 PM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
Posts: 7,344
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Typical ground loop issue.
1. Make certain alternator has a good, corrosion free ground path to firewall/forest of tabs. Check alternator, engine ground straps.
2. Make certain every connection to or from the intercom is floated (insulated) from the airframe (e.g., do not use the airframe for completing any connections). Fiber washers at and inside the holes for all jacks. I have seen CD players which work noise free when run on internal batteries but pick up a lot of alternator whine when plugged into a cigar lighter (completing the ground loop).
What brand intercom/audio panel are you using?
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  #16  
Old 03-04-2021, 03:04 PM
smithflys23 smithflys23 is offline
 
Join Date: Feb 2017
Location: Jupiter
Posts: 220
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Quote:
Originally Posted by BobTurner View Post
Typical ground loop issue.
1. Make certain alternator has a good, corrosion free ground path to firewall/forest of tabs. Check alternator, engine ground straps.
2. Make certain every connection to or from the intercom is floated (insulated) from the airframe (e.g., do not use the airframe for completing any connections). Fiber washers at and inside the holes for all jacks. I have seen CD players which work noise free when run on internal batteries but pick up a lot of alternator whine when plugged into a cigar lighter (completing the ground loop).
What brand intercom/audio panel are you using?
Bob, thanks again!

Iím going to have to take a look at what Iíve got under the cowling. As this conversation has evolved, Iíve been become more suspicious of some of the big ticket items. IE, the alternator, engine grounding, and battery wiring. I suspect this is where the issue is originating. This is especially frustrating considering I paid a substantial sum to have everything wired by a ďproĒ. Iíve been chasing nuisance problems for some time now.

I donít think there is any corrosion due to the relative young age of my airplane.

Everything I have is recent manufacture Dynon, with the exception of my Garmin G5 back up instrument.
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  #17  
Old 03-04-2021, 05:01 PM
pulsar pulsar is offline
 
Join Date: Sep 2018
Location: NY
Posts: 34
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Quote:
Originally Posted by smithflys23 View Post
I donít think there is any corrosion due to the relative young age of my airplane.
Not saying itís the issue here... but donít underestimate corrosionís ability to mess up your life in short order. At least itís easy to check.
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  #18  
Old 03-04-2021, 06:09 PM
smithflys23 smithflys23 is offline
 
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Posts: 220
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Iíll be sure to check. Like you said, this is easy.
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  #19  
Old 03-09-2021, 01:43 PM
SPB W10 SPB W10 is offline
 
Join Date: May 2018
Location: LINCOLN NEBRASKA
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Here is an update to our audio noise.
While "reracking" the center stack radios, checking for pin condition and treating with corrosion protection, the back rectangular connector assembly of the Garmin GMA 340 audio panel tray was found (visually) with all screws loose. This is where shields and grounds are terminated and this seems to have been the problem for a long time. The speaker and headphones do not have the alternator whine any more. We won't list all of the other components replaced, tested and grounds cleaned, phone jack and aux audio input jack insulators checked etc.
Whewww!
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  #20  
Old 03-09-2021, 02:40 PM
smithflys23 smithflys23 is offline
 
Join Date: Feb 2017
Location: Jupiter
Posts: 220
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I believe my connections are good, but definitely something to check.
I think Iíve got a battery or engine grounding issue that I need to address.
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