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GMA340 - Crackling

chazking

chazking

Well Known Member
Need some help in resolving a nagging issue.

I have a severe crackling in the comm system that is beyond annoying, it can drown-out ATC; they can hear me, but I cannot hear them due to the crackling. Squelch can minimize the annoyance, but eventually, that no longer works. It was so bad, I had to send my 430W to Garmin for repair (msg: COM Needs Service). The crackling continued with a new GPS.

The RV-10 was put into service Mar 2011 & it has just over 50 hours on it. This issue began about 8 hours ago, so all was well until then. Avionics wired by Pacific Coast Avionics.

Here's the background / trouble shooting, thus far:

Crackling:
? Occurs during magneto drop

? On GMA340:
➢➢?? Stops when the GMA340 is turned-off.
➢➢?? Re-seating the GMA340 has no effect.
➢➢?? Shielded wires appear to be properly grounded.

? Occurs on pilot & co-pilot headsets;
➢➢?? Separately & simultaneously.
➢➢?? Intercom works with either headset.

? Occurs when doors are "banged" & engine not running.
➢➢?? Does not occur when eng not running & doors not "banged."
➢➢➢➢ (Note: sounds crazy, but banging either door causes the crackling when the eng is running or not running.)
➢➢?? Door latch notification system from Vans not installed

? All wiring does not exhibit any weaknesses, e.g., no fraying, etc..

? All grounds are in place & show no deterioration.

? Antennas are solid (2 RAMI & 1 Archer).

The "banging" door scenario is the only one repeatable.

So, has anyone had this type of issue? New troubleshooting ideas?
 
I'm pretty good around electronics and would be happy to take a look - if you are close by. This is one reason not to try to be too cute about posting your location!

Do you have trouble hearing the com when the intercom volume is all the way down, but you can hear it okay in fail-safe (340 off)? If so I'd guess it is internal to the 340.
 
GMA340 - Crackling - Solved

Thanks for the offers & suggestions. The banging door scenario provided the break in the troubleshooting. Seems the mic side of the right passenger seat was shorting on vibration. I did a bit of reconfiguration / repair & it has not repeated.

My main future issue revolves around replacing the mike / headset jacks with industrial strength components. Suggestions welcomed. I will post another thread asking for advice.

In the future I would suggest that the first order of troubleshooting for "crackling" is look @ all the mic connectors, not just the pilot & co-pilot.

The value of this troubleshooting is I know the panel very well @ this point & as I replace the 4500s (EE & EF) with 5600s I expect to have a better sense of proper physical & electrical architecture.
 
I had this once before, for me it was the airplane side of the jacks. The nut that holds the jack in place was loose so the jack was moving around and grounding out against the metal it went through.

Make sure that nut is TIGHT......that is what fixed it for me......
 
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