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  #1  
Old 03-11-2020, 08:53 PM
SPB W10 SPB W10 is offline
 
Join Date: May 2018
Location: LINCOLN NEBRASKA
Posts: 30
Default Noise & Data Problem

We have electric whine in the Garmin 530 & 430com headsets and cabin speaker. We have a Chrysler alternator with a noise filter attached to the case and a #6-gauge wire from the alternator ground to the starter mount bolt. The starter has an 0 gauge ground wire routed to cockpit structure.
The JPI EDM 700 downloaded data is unusable. Cylinders #1, #3 & #5 EGT and CHT have ?noise? near the harness we have been told by SAVVY Analysis.
The magneto harness has been checked for shorting to shield and separated from the EGT CHT harness and there was no change.
The alternator field and output wiring are routed under the cylinders which gives plenty of distance from the data harnesses.
Could the alternator noise and the data harness problem be related somehow?
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Steven B.
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1980's RV-3 & RV-4 Build Support
Lincoln, NE
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  #2  
Old 03-11-2020, 09:24 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,993
Default

Quote:
Originally Posted by SPB W10 View Post
We have electric whine in the Garmin 530 & 430com headsets and cabin speaker. We have a Chrysler alternator with a noise filter attached to the case and a #6-gauge wire from the alternator ground to the starter mount bolt. The starter has an 0 gauge ground wire routed to cockpit structure.
The JPI EDM 700 downloaded data is unusable. Cylinders #1, #3 & #5 EGT and CHT have “noise” near the harness we have been told by SAVVY Analysis.
The magneto harness has been checked for shorting to shield and separated from the EGT CHT harness and there was no change.
The alternator field and output wiring are routed under the cylinders which gives plenty of distance from the data harnesses.
Could the alternator noise and the data harness problem be related somehow?
This sounds more like a ground issue somewhere. Would probably start by verifying engine to airframe ground conductivity. Also be sure the alternator case to crankcase shows 0 ohms.

Larry
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  #3  
Old 03-19-2020, 05:00 PM
JLuckey JLuckey is offline
 
Join Date: May 2009
Location: Southern California
Posts: 25
Default

1. Does the whine change with engine RPM?
2. Has the whine always been there or did it start recently?
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  #4  
Old 03-09-2021, 01:33 PM
SPB W10 SPB W10 is offline
 
Join Date: May 2018
Location: LINCOLN NEBRASKA
Posts: 30
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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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1980's RV-3 & RV-4 Build Support
Lincoln, NE
2021 DUES PAID THOUGH EXEMPT
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