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Warm-up Problem

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dalamphere(at)comcast.net
Guest

Posted: Wed Dec 16, 2009 12:21 pm Post subject: Warm-up Problem

Here are the symptoms/conditions:



1. King KX125, Plane Power 60a alternator, Lycoming O-320-D2A, PS 

Engineering 1000II intercom, Lightspeed 20XLc headsets.



2. After engine startup initially while the battery is being re-charged, if 

I press the PTT button to transmit to unicom, I'll hear a very loud 

hi-pitched whistle in my headset (side-tone)- my guess is it's around 8Khz. 

It doesn't appear that transmitting gets through.



3. The radio recieves very clearly during this period - say listening to 

AWOS for example.



4. With the intercom off, it does the same thing.



5. After the battery is recharged, and from then on in the flight (including 

re-starts after re-fuel) the radio transmits and recieves clearly.



6. There is a 2.2uF at the positive output lead of the alternator to ground. 

There is a noise filter between the main bus and avionics buss.



7. A single point multi-tab ground is used.



Any ideas what to look at next??



Dave

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deene(at)austin.rr.com
Guest

Posted: Thu Dec 17, 2009 7:56 am Post subject: Warm-up Problem

You should check your alternator to see if the diode bridge is OK.  If a diode fails, then the output from the alt will be very noisy and especially at higher output levels…  

   

Deene Ogden  

RV8  

CFII, MEI, CFIG  

   

        [quote][b]

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dalamphere(at)comcast.net
Guest

Posted: Thu Dec 17, 2009 9:54 am Post subject: Warm-up Problem

If that was the case, wouldn't the frequency of  the shriek be lower?? - and continue to be noisy all the time? It ouzzles me  that on stops where I re-fuel and startup again - there's no noise right after  startup...

  

 Thanks for your input - I thought I'd get a lot  more suggestions from the group. Everyone must be shopping 

  

 Dave (N365DL)

 PS. 40.5 hrs today! Phase 1  complete!!!

 [quote]   ---

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