View Full Version : Noise from EFIS in Headset

05-12-2010, 12:47 PM
I have a Noise of the Fan and the Dimmer in my Headset (Intercom). If the EFIS is on Backuppower the Noise is gone. If i regulate the Dimmer the Noise is gettig high and low like the Dimer. If i put the Dimmer to 100 the Noise of the Dimmer is gone.


Rob Hickman
05-26-2010, 02:13 PM
1. If you disconnect the audio wire from the EFIS do you still get it?
2. What intercom are you using?
3. What is your current buss voltage? The noise reduction in the PS Engineering units does not turn on below 12 Volts.

07-18-2010, 11:07 PM
Hy Rob,
1. If i disconnect i don!t get it anymore
2. The Intercom ist a Filser Com with built in Intercom ( http://www.funkwerk-avionics.com/cms/upload/Downloads/Flyer-ATR833.pdf ) with a VX-aviation 10 Channel Audio Mixer ( http://www.vx-aviation.com/documents/AMX-2A_install.pdf) in front.
3. The buss voltage is 13.2 Volts

I have tryed eveerything this Weekend, the Noise is still there.


06-10-2011, 11:32 AM
I'm getting white noise from my AF-3500EF. It is coming in to my PS Engineering PMA 5000EX audio panel on the EFIS audio warning line, which I routed into an AUX input on the audio panel. I've turned everything else in the plane off, and the noise goes away if I turn off the EFIS. If I turn off the AUX input on the audio panel the noise also goes away. It sounds like basic white noise, about 2x as much as I get from the audio panel itself. All the other stuff hooked to the audio panel isn't making any noise.

The audio alerts are playing OK. I'm running the airplane on a clean linear power supply at 13.6 volts.

The only really odd thing that I noticed is that when I pulled the EFIS fuse to turn it off, the noise got much louder and a little bit "squealy" when the EFIS was running on its battery. I assume this is the switching power supply in the EFIS.

I'm going to check the shielding tonight, but I'm wondering if I need a filter of some sort... maybe a common mode filter?

Thanks for any info,

dave gribble

Trevor Conroy
06-13-2011, 08:36 AM
Dave, an audio filter may help but do check that shielding. It should only be grounded on one end (typically on the audio panel end).

06-13-2011, 10:34 AM
Thanks Trevor - I'm using a pre-made harness that came with the AF-3500. I grounded the shield at the audio panel end for sure.

On the EFIS end, there is a connection called "Audio GND" on pin 16 of the 25 pin D connector. This is drawn with a dashed line to the sheild of the audio wire out of the EFIS. I haven't yet checked to see if this is connected in the pre-made cable yet.

I don't know if I'm being overly picky - should I hear additional white noise coming from the EFIS? It seems like a lot.