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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 25627
Location: Livermore CA USA
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 Posted: Fri Oct 25, 2013 7:48 am Post subject: New Alternator, New Whine... |
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Dear Listers,
I just finished the Conditional Inspection on the RV-6. The day after I got everything buttoned up and went out for a test flight, the alternator started to flake. The old alternator was some no-name brand thing the original builder got from somewhere. It never had enough output to power up everything during taxi and landing. I suspect that it was probably a 40amp unit but there are no markings on it so I don't know for sure. It had an external regulator; one of those GM-style, two-wire gems.
So, I replaced it with a brand new PlanePower 60amp internally regulated and OVP'd unit. The same one, in fact that I have on the RV-8. The good news is that it really kicks butt and puts out plenty of power even at idle to keeps everything powered up and the voltage level around 13v (max current draw is about 36amps, so the new alternator has plenty of headroom). With the lights off, or at higher power settings it puts out a nice solid 14.1 volts or more. I'm super happy.
Now the bad news. Now I have a loud alternator whine in the headphones! It's particularly noticeable around 800-1100 RPM. The interesting thing about it is that adjusting the volume of the Intercom, the Nav/Com, or the Stereo has no impact of the volume of the whine. Only adjusting the two volumes (L+R) on the Bose A20 headset dongle will change the volume level of the whine. That seems like its the Bose that not liking the noise, but...? In the RV-8, I had the exact same alternator, VP-200, Intercom, stereo, etc. with NO alternator whine. However, I didn't buy the Bose A20 headsets until after I got the RV-6, so I never used them in the RV-8. The RV-8 I had the previous model of headset, the Bose X. I'm going to give the Bose X headphones a try in the RV-6 and see if I hear the whine.
The A20's are much better headphones than the X's, so I really want to keep using them, but that whine is pretty insidious. I worry that I may have the same issue using the A20's in the RV-8 when I get it flying again.
I've been really careful, particularly in the RV-8, to run separate grounds to everything and not use the airframe as a ground. In the RV-6, since it was already built, I had less opportunity to do that. However, on the instrument panel, since I rebuilt that from scratch, most everything electronic got its own ground to the new grounding tree. Maybe I need to run a ground wire out to the alternator?
Any insight you can lend would be most appreciated.
-
Matt Dralle
RV-8 #82880 N998RV "Ruby Vixen"
http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log
http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: 172+ Hours TTSN - Rebuilding Fuselage After Landing Mishap...
RV-6 #20916 N360EM "The Flyer"
http://www.mattsrv6.com - Matt's RV-6 Revitalization Log
Status: 180+ Hours Since Purchase - Upgrades Complete; Now In Full Flyer Mode
Matt's Livermore Airport Live ATC Stream!
Check out the live ATC stream directly from my hangar at the Livermore
Airport. Includes both Tower and Ground transmissions. Archives too!
For entertainment purposes only. http://klvk.matronics.com
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skywagon
Joined: 11 Feb 2006
Posts: 184
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| Posted: Fri Oct 25, 2013 9:17 am Post subject: New Alternator, New Whine... |
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Matt,
Best guess is that the higher current alt. is insufficiently grounded and is
radiating via its current ground. For a test, I would fire up the RV to the
engine rpm that causes the worst phone noise and then, start shutting down
electrical loads reducing alt. current output. If the noise also
diminishes, then, I would install a better grd. buss to the alt.
Dave
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dave.saylor.aircrafters(a
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| Posted: Fri Oct 25, 2013 9:44 am Post subject: New Alternator, New Whine... |
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I've had a similar whine with a PP alternator and Zulu headsets. Â Same fix, I slide the L&R volumes down to about mid and adjust everything else to fit--the whine is much less. Â I've tried grounding the alternator case without success. Â The whine gets louder with more output from the alternator. Â I'm all ears, but the fact is I've learned to live with it.
Dave Saylor
831-750-0284 CL
On Fri, Oct 25, 2013 at 10:16 AM, David Lloyd <skywagon(at)charter.net (skywagon(at)charter.net)> wrote:
[quote] --> AeroElectric-List message posted by: "David Lloyd" <skywagon(at)charter.net (skywagon(at)charter.net)>
Matt,
Best guess is that the higher current alt. is insufficiently grounded and is radiating via its current ground. Â For a test, I would fire up the RV to the engine rpm that causes the worst phone noise and then, start shutting down electrical loads reducing alt. current output. Â If the noise also diminishes, then, I would install a better grd. buss to the alt.
Dave
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nuckolls.bob(at)aeroelect
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| Posted: Fri Oct 25, 2013 11:40 am Post subject: New Alternator, New Whine... |
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Now the bad news. Â Now I have a loud alternator
whine in the headphones! It's particularly
noticeable around 800-1100 RPM. Â The interesting
thing about it is that adjusting the volume of
the Intercom, the Nav/Com, or the Stereo has no
impact of the volume of the whine. Â Only
adjusting the two volumes (L+R) on the Bose A20
headset dongle will change the volume level of
the whine. Â That seems like its the Bose that
not liking the noise, but...? Â In the RV-8, I
had the exact same alternator, VP-200, Intercom,
stereo, etc. with NO alternator whine. Â However,
I didn't buy the Bose A20 headsets until after I
got the RV-6, so I never used them in the RV-8.
The RV-8 I had the previous model of headset, the
Bose X. Â I'm going to give the Bose X headphones
a try in the RV-6 and see if I hear the whine.
These symptoms scream (or should I say whine?) GROUND LOOP!
I've been really careful, particularly in the
RV-8, to run separate grounds to everything and
not use the airframe as a ground. Â In the RV-6,
since it was already built, I had less
opportunity to do that. Â However, on the
instrument panel, since I rebuilt that from
scratch, most everything electronic got its own
ground to the new grounding tree. Â Maybe I need
to run a ground wire out to the alternator?
I'd check to see that ALL grounds to the Bose system,
audio AND power(-) are grounded at the same place
power(-) and audio for the intercom are grounded.
Your 60A alternator isn't bad and probably isn't
installed wrong . . . it's just capable of putting
more noise into the loop that existed before the
alternator was replaced.
The single point ground concept is often mis-understood
to mean signal grounds only. Given that many if not most
pieces of avionics have an internal common chassis ground
for both signal and ground, you need to treat power grounds
the same as signal grounds.
Do you have a dedicated black-box ground on the
instrument panel or does everything go to a firewall
block? If so, your two points of ground on the airframe
are chassis grounds on the panel and wired grounds
on the firewall.
Bob . . .
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