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Topic Options
#406640 - 09/20/20 09:12 PM Electronic buzzing in panel with master off
Kentucky Captain Offline
Gold Pilot

Registered: 06/13/14
Posts: 1379
Loc: Louisville, KY
This is a continuation of the post that I just made in the Tech Question section but this issue is electronic in nature.

Upon landing at 2I3 and powering everything down, we experienced an electronic buzzing sound emanating from the panel. The switch and the master were off. There is no vacuum pump or instruments. I could not locate the source but it was fairly loud and I would guess it was somewhere in the 400 to 500 Hz range. It quit for a few seconds and then started back up. I unplugged all of the headsets as it sounded something like the feedback you get when the microphone gets too close to the headset earpieces. I started pulling circuit breakers and it quit when I pulled the one for the JPI EDM900 engine monitor. I don't know if that was the culprit or it finally gave up at that point.

I didn't hear it anymore there on the field or after we got back to Bardstown. Very strange. Anyone ever heard of something like this?

Other equipment in the panel:

Aspen Pro Max 1000 PDF
Aspen Pro Max 1000 MDF
PS Engineering PMA450 audion panel
STEC 55X autopilot
Lynx L3 NGT9000+ with active traffic
Avidyne IFD540
Garmin GNC255A nav/comm

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#406642 - 09/20/20 11:07 PM Re: Electronic buzzing in panel with master off [Re: Kentucky Captain]
SeaProbe Offline
Second in Command

Registered: 06/30/14
Posts: 216
Loc: California
Hmmm. 400-500Hz sounds like a cooling fan. It could be scraping or rubbing in its housing.

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#406643 - 09/20/20 11:26 PM Re: Electronic buzzing in panel with master off [Re: SeaProbe]
Flubber4.0 Offline
Gold Pilot

Registered: 08/22/14
Posts: 1241
Loc: blue marble
One of the numerous fans in your panel running on battery to cool down electronics.
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#406671 - 09/22/20 09:17 PM Re: Electronic buzzing in panel with master off [Re: Flubber4.0]
Kentucky Captain Offline
Gold Pilot

Registered: 06/13/14
Posts: 1379
Loc: Louisville, KY
Originally Posted By: Flubber4.0
One of the numerous fans in your panel running on battery to cool down electronics.


I was thinking that all of the fans turned off when the master goes off but I guess it is possible. I'm assuming that there are a lot of fans. The whole Aspen outer cases are a big heatsink but I do think that they have fans. It didn't seem to come from the left side of the panel but who knows how the sounds get redirected around in there. I believe that most of the equipment in the center stack has a fan also.

It wasn't a particularly hot day, only about 74 degrees but sunny. I'll kick that around some. Thanks,
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