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Regulator/Alternator whine in intercom.

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We have a 225 for our Taylorcraft, and are using the intercom, with audio input for music. I see no reason that the PM 3000 couldn't be removed from the system entirely.

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That's what I'm thinking.  Just bypass the PM 3000 totally.  Can't take too much to do that (famous last words!)

I just don't know what I could put in that place.

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Dang, until I can repeat aux audio connectivity with just the 225, it may be wired differently than Tom’s T-Craft, I need to use both- 3000 for music when desired.  Plus need to check pax side function..

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The passenger headset and auxillary/XM radio are wired to the 3000 only in my airplane.

Shouldn't take much to switch those wires over.

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OKENT-Just confirmed and I have the same setup.

For my flying, usually solo, the 225 alone cuts down on unwanted noise. I’ll use the 3000 on occasion when music is desired and it drowns out noise. 

Is rewiring still in the cards?

 

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Yes, planning on a rewire.  I'm almost due for an oil change and will have it done then.  Will wire the AUX switch to toggle the XM radio.

 

Edited to add that talking with Rex Johnson, he didn't think it would be a big deal to change that wiring.

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My switch has XM and Aux positions. Currently don’t have Xmas subscription. Are you thinking wiring the 796 XM to the 225 would play music thru the 225 IC as well as PTT?

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Yes, I listen to XM radio almost every time I fly.  I like having the ability to flip off the XM radio if things get busy and if it's wired into the 225 I want to wire in that switch to do the same.

There's an AUX setting in the 225 but it is a few menu's deep.  The switch would be really handy.

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Keep in mind that ground loops can generate noise too.

The audio system in flight designs leaves a lot to be desired; there's wires with no shielding or twisted pair, and ground connections in many places when instead there should be only a single branching ground path on audio connections.

You may wish to consider using isolation transformers if you know how. Due to the complexity of the subject, I can only point to this and suggest you talk to someone about it, or do a deep dive into the theory in their use.

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Thanks for the tech thought. Dang, these design/production issues trump useage/maint issues and should be on FD to resolve. Noticed a FL Flight School went with Technam…wonder if they factored these kinds of gremlins in or flying characteristics for students?

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There are other light sport aircraft with rotax engines that have the whine as well. But usually, it's the carb version. Haven't messed it with the injected version much. I've always solved it with a large filtering capacitor and getting grounds as clean as reasonably possible.

My boss has a Cirrus SR22T that I fly, and it has a whine from the air conditioner.

Edit: also consider doing voltage drop tests on the grounding. The lower, the better. A few tens of milivolts at most is best, but realistically seeing a hundred milivolts is common.

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