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rick(at)beebe.org
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 Posted: Sat Sep 12, 2020 8:05 pm Post subject: Fwd: Re: Re: Alternator/Strobe whine |
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So it is alternator whine. It's present when the strobes are off. When they're on, it does warble a bit. There is a bit of strobe noise with both alternators off and just the battery on but it's not obnoxious at all. There's no noise at when running on the backup alternator.
--Rick
-------- Forwarded Message -------- Subject: Re: Re: Alternator/Strobe whine Date: Tue, 8 Sep 2020 19:47:49 -0400 From: Rick Beebe <rick(at)beebe.org> (rick(at)beebe.org) Reply-To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com) To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
I'll be back at the plane on Saturday and I will do some controlled tests. The noise pitch is definitely in sync with the strobes. When I turn the main alternator off the noise goes away completely. My memory is that it also goes away when I turn the strobes off (main alternator on), but I'm not sure if there's a residual whine.
--Rick
On 9/8/2020 4:41 PM, Robert L. Nuckolls, III wrote:
| Quote: | Alternator, strobe or both?
Alternator whine is almost always a ground loop issue.
Pitch of whine will go up and down with engine rpm.
It often gets louder when alternator loads are highest
like right after starting engine (recharging battery)
and all loads turned on.
Strobe whine pitches up and down in synchronization
with flashes from the strobes and is generally of
constant volume.
Which one(s) disappear when appliance is OFF.
Alternator, strobe or both?
Bob . . . |
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user9253
Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan
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| Posted: Sun Sep 13, 2020 2:33 pm Post subject: Re: Fwd: Re: Re: Alternator/Strobe whine |
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Check the AC component of the alternator output.
It should be less than 1 volt AC. More than that means a diode is bad.
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Joe Gores |
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nuckolls.bob(at)aeroelect
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| Posted: Sun Sep 13, 2020 5:24 pm Post subject: Fwd: Re: Re: Alternator/Strobe whine |
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At 11:03 PM 9/12/2020, you wrote:
| Quote: | So it is alternator whine. It's present when the strobes are off. When they're on, it does warble a bit. There is a bit of strobe noise with both alternators off and just the battery on but it's not obnoxious at all. There's no noise at when running on the backup alternator.
--Rick |
This about has to be a grounding issue.
Refresh my memory. What kind of airplane?
Can you describe your ground system? Conforms
to recommendations in Z15/Chaper 5 in the
'Connection?
Bob . . .
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rick(at)beebe.org
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| Posted: Mon Sep 14, 2020 7:42 am Post subject: Fwd: Re: Re: Alternator/Strobe whine |
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On 9/13/2020 12:10 PM, Robert L. Nuckolls, III wrote:
| Quote: | At 11:03 PM 9/12/2020, you wrote:
| Quote: | So it is alternator whine. It's present when the strobes are off. When they're on, it does warble a bit. There is a bit of strobe noise with both alternators off and just the battery on but it's not obnoxious at all. There's no noise at when running on the backup alternator.
--Rick |
This about has to be a grounding issue.
Refresh my memory. What kind of airplane?
Can you describe your ground system? Conforms
to recommendations in Z15/Chaper 5 in the
'Connection?
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It's a GlaStar. Battery is in the back. The negative cable runs to a terminal strip mounted on the sidewall on the copilot side. Most non-avionics things such as lights, boost pumps, etc, are grounded there. When I re-did the panel I put an avionics ground block on the back of the panel. It's connected via redundant wires to the ground terminal strip.
The other end of the terminal strip connects to another thick wire the firewall which connects to the engine. I believe the starter, engine and alternator are gounded there but I have to verify. That alternator is one of the few things I did not touch in the panel re-do. I'll be opening things up for the condition inspection in a couple weeks and I'll take a very close look at how that alternator is wired.
--Rick
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