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Regulator/Alternator whine in intercom.


okent

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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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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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  • 3 weeks later...

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 thousandths milivolts at most is best, but realistically seeing a hundred milivolts is common.

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  • 4 months later...

Edited to add that the whine is still there after annual.  A&P will be calling PS Engineering to see if anything can be done.  They swapped out for a new PS3000 and no joy.  Would like to avoid wiring directly to the garmin radio.  Will post when I have more info.

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  • 1 year later...
On 1/17/2022 at 4:26 PM, okent said:

Edited to add that the whine is still there after annual.  A&P will be calling PS Engineering to see if anything can be done.  They swapped out for a new PS3000 and no joy.  Would like to avoid wiring directly to the garmin radio.  Will post when I have more info.

Any luck?

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  • 3 weeks later...

I had a similar whine show up one day as I was warming up.  Eventually the EFIS died followed by the radio and transponder.. on previous flights before these signs I was getting a “high fuel pressure “ warning, despite any other symptoms. Red herring perhaps.  Any way in consultation with a local A&P, he suggested simply pulling the voltage regulator plug and reconnecting it.  IT WORKED!, including stopping the fuel pressures warning. Major bugger to pull out the plug without damaging it, but with persistence I did it.  
Unrelated, I had two temp probes showing wild swings in readings.  Obviously loose connections.  Fixed by putting them both in slight traction by pulling them through their respective zip ties.  Ta da! Fixed.  
 

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