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  #1  
Old 05-04-2015, 08:29 AM
MikeyDale's Avatar
MikeyDale MikeyDale is offline
 
Join Date: Aug 2012
Location: Garden City Texas
Posts: 878
Default Radio Noise

I have a question for someone who knows more about magnetos than me, which is just about everybody I guess. My RV7 was ready for its first flight last Tuesday but unfortunately the weather was crappy that day and I had to go back to work for a two week hitch on Wednesday! I have a little time to think about solving my a little Magneto problem I have....I have two Bendix S4LN mags on my pre owned IO-360 B1E. I thought they were rebuilt 75 hrs ago but after re examining my engine documents, it says "Repaired as Needed". I installed new harnesses on each mag (harnesses came assembled with new caps) along with 8 new tempest fine wire plugs. I have one Dynon Comm Radio and Intercom....On run up mag check, I get a 60 RPM drop on each mag. I have never gotten a bad check from either mag unless I had a fouled plug. I have run my engine more than a several times and managed to foul the old plugs before I got my idle mixture right. I have a ticking noise coming from the right mag that follows my engine RPM. Not so bad at 118.025 atis but the com 122.8 is worse. Completely silent on left mag only. Alternator on or off makes no noise. After doing a search on the problem, I ordered and installed a new condenser on the right mag thinking surely it would cure the noise. No such luck, noise level did not change. The points looked OK when I changed the condenser. The noise was the same before I installed the new plugs so I'm doubting a high resistance in a plug. I have not checked the resistance in the new plugs or the new harness wires yet. If I cant find the problem, I am considering ordering a noise filter from ACS http://www.aircraftspruce.com/catalo...sMagFilter.php and trying it out. Does anyone out there have any suggestions? Thanks in advance!
Mike
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  #2  
Old 05-04-2015, 09:48 AM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,767
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I'd check the shield connections on the harness and also the right P lead first.
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  #3  
Old 05-04-2015, 10:13 AM
mahlon_r mahlon_r is offline
 
Join Date: Jan 2005
Posts: 1,024
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It is not uncommon to need a noise filter on the pleads of that style mag. However from your description it sounds like your issue is with a single lead plug not common to the mag. As the previous poster stated. You should check the shielding grounds on all the ignition leads from that mag. Sounds like you may have one that isn't grounded properly.
Good Luck,
Mahlon
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