Robertmpaille Posted November 14, 2018 Share Posted November 14, 2018 (edited) When keying the mic. I get magneto noise in headset, left mag. Only. Started about five hours ago, has worked fine for sixteen years. The mag. filters are mounted on the upper motor mount, has four small grounds plus shielded p leads. Clamp was a little lose, cleaned all grounds, p lead, clamp ,with fine emeroy cloth, noise went away for about one hour, and now it's back! Mag had 500hr insp. about 150 hr ago. Maybe run a ground wire from magneto point cover plate to clamp on filter and mount? Suggestion would be appreciated. Radio icon a200. How do you check noise filter with ohm meter? Edited November 14, 2018 by Robertmpaille Quote Link to comment Share on other sites More sharing options...
Kent Ashton Posted November 14, 2018 Share Posted November 14, 2018 The problem of noise comes up from time to time on the Aeroelectric list. You can do a search of their archives here http://www.matronics.com/search/ or join the list and ask Bob Nuckolls. He is pretty good about answering questions. My book "The Magneto Ignition System" by John Schwaner says "The P lead should be shielded to prevent low frequency (AM band) radio interference caused by voltage fluctuations in the coil's primary circuit" . . ."the shielding needs a low impedence path to ground at both ends with the ground at the magneto end being the most important" (at p. 76). There is more but get the book and read the rest on shielding. It sounds like you might have disturbed the P lead shield. https://books.google.com/books/about/The_Magneto_Ignition_System.html?id=F0PSxP_wB5oC Quote -KentCozy IV N13AM-750 hrs, Long-EZ-85 hrs and sold Link to comment Share on other sites More sharing options...
mquinn6 Posted November 15, 2018 Share Posted November 15, 2018 Robert, You also might want to check your wires to the spark plugs. I have seen where you will see a spark in the dark with the cowl off! Check your wire routing and make certain you have no "stray" sparks going on. Only way that I know to check noise is with an Oscilloscope - or a speaker like your headset ;-) Quote Link to comment Share on other sites More sharing options...
Robertmpaille Posted November 16, 2018 Author Share Posted November 16, 2018 (edited) I believe I solved the problem, the left p lead shielding was not getting a good ground. The mag. Filter being mounted on the motor mount with ms 21919 1/2" clamp , could not get clamp real tight. Ran a ground wire from magneto cover plate to left filter on motor mount. Took short flight. No magneto noise from left or right!! Plus p leads were switched left to right right to left, now correct. Edited November 16, 2018 by Robertmpaille Quote Link to comment Share on other sites More sharing options...
mquinn6 Posted November 16, 2018 Share Posted November 16, 2018 Congrats! I am glad you found it! Quote Link to comment Share on other sites More sharing options...
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