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  #1  
Old 06-14-2017, 06:30 AM
RudiGreyling's Avatar
RudiGreyling RudiGreyling is offline
 
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Default Sudden start of terrible feedback whine? GTN650 + SL30 + PMA9000EX

Aviators,

I need serious help please. On Saturday, my GTN650 + SL30 + PMA9000EX setup (I installed myself from Stein Air supplied harnesses and equipment) started acting up, out of the blue, after 150hours of perfect operation.

On transmission, I suddenly started getting a terrible loud feedback whine on any of the 2 radios GTN650 or SL30 (Zulu headsets)

I spend the whole of Saturday and Sunday, frustrating trying to trace the problem and fiddling with the settings, checking wiring / earths, swapping headsets, to no avail, so I am staggering in the dark.

Does anybody have some guidance on root cause for feedback whine on transmission and where to pinpoint the search?

It is so bad that fellow radio users and tower complain back to me about it. Never mind the ring in my ears...

Thank you in advance.
Kind Regards
Rudi
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Last edited by RudiGreyling : 06-14-2017 at 06:47 AM.
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  #2  
Old 06-14-2017, 07:23 AM
Mich48041 Mich48041 is offline
 
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Concentrate on the PMA9000EX and its connections.
Shut off electrical power to the PMA9000EX. Then check com1 operation.
Good luck.
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  #3  
Old 06-14-2017, 07:25 AM
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Walt Walt is offline
 
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First things I would look at are things that are common to both radios:
Start with power, voltage good (14V+)? Is it the same with alt on/off?
Grounds, probably ok but double check.
Audio panel, does it do with the panel turned off? (should fail safe to #1 com).
Panel jack/plugs.
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  #4  
Old 06-14-2017, 07:42 AM
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Snowflake Snowflake is offline
 
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Did it happen in-flight, ie. one transmission it was fine and the next it changed? Or did it change between two flights?

If it's the former, i'd be looking for a wire that has popped loose, or maybe a shield connection. Then start eliminating electronics one by one by turning them off (or removing power leads if they're all on one "master") individually.

If it was between flights, i'd look at what you did differently first... Did you get a new cell phone? Any changes to any other electronics in your EDC? Tablet, e-cigarette, etc.?
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Old 06-14-2017, 08:12 AM
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flytoboat flytoboat is offline
 
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I traced recent intermittent noise in my Garmin GTR200 radio/intercom system to a panel mounted USB power point used to charge my iPad in flight. on the ground, I started turning off and back on, each switch one at a time. When I turned off the USB charger the noise went away.
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Old 06-14-2017, 08:19 AM
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FORANE FORANE is offline
 
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Does this occur on passenger PTT also?
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  #7  
Old 06-20-2017, 12:30 AM
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RudiGreyling RudiGreyling is offline
 
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I have found the Culprits, but not the Root cause yet.

It was 2, YES 2, of my lightspeed Zulu headsets. (Yes the sets I used to swap out to determine if it was a headset problem, murphy's law!)
My other 2 Lightspeed Zulu headsets (I have 4 it total) (older versions) work perfectly, so it is the 2 newer headsets.

I started a new thread to keep those together:
http://www.vansairforce.com/communit...d.php?t=150630
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Last edited by RudiGreyling : 06-20-2017 at 01:08 AM.
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