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Whining Radio

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iflyhawaii2(at)yahoo.com
Guest

Posted: Sun May 28, 2006 10:33 pm Post subject: Whining Radio

I'm chasing down a new noise in the headset on my 60 hour RV-6A with the Z-11 architecture. The whine starts when I turn the radio on and will go off when the alternator switch is turned off (or, of course, if the radio goes off), and is RPM dependent.  



   The noise is not load dependent, i.e. after the battery is topped off ( I have an ammeter) the whine is still the same intensity.  The funny thing is that after an hour flight the noise intensity is much less (maybe only 1/3 the level) than the first 10-20 of flight.  Is the alternator is now "warmed up" and producing less noise?

   I'm thinking the source is the alternator (#$%&* Van's special) and the victim is the radio, but how and where is the RF leaking and absorbing?



More Info:

B & C linear regular inside the cockpit.

All fat wire seperated from skinny wires.

Recently did some work on the brake hoses and could have bumped a wire.

On day one of this machine I did have a very mild whine on the intecomm that went away with battery top off. (new noise is not affected by intercomm settings.)



   Should I be thinking about wire routings, loose connections, grounds first?  Then check the power wire from a clean source?



Please help. 

Dumfounded in Honolulu.

Greg



		

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lhelming(at)sigecom.net
Guest

Posted: Mon May 29, 2006 6:18 am Post subject: Whining Radio

Like you report, I too developed a whine --and-- within a month my 

alternator failed.  This all happened shortly after I did my night flights 

where I stressed my alternator to 90% of its limit by having all my 

electronics on while doing the required take offs and landings.  I plan to 

install a larger alternator that will have a rating about twice what my 

maximum draw need will be.  I was able to replace the 30A Vans alt. with the 

same type that I purchased at the local AutoZone store.  I believe my 

original 30A came from a Suzuki of some sort about 1987.  For now with 

replaced alt. I do not turn all the lights on at one time.



It is in the archives somewhere and I believe Sam Buchanan made a post about 

it.



Larry in Indiana

---

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brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Mon May 29, 2006 7:43 am Post subject: Whining Radio

On May 28, 2006, at 11:23 PM, Greg Grigson wrote:



 	  Quote: 	
		   

 <iflyhawaii2(at)yahoo.com>



    I'm chasing down a new noise in the headset on my 60 hour RV-6A  

 with the Z-11 architecture. The whine starts when I turn the radio  

 on and will go off when the alternator switch is turned off (or, of  

 course, if the radio goes off), and is RPM dependent.


	


In all probability one or more diodes in your alternator have failed.  

This is usually a precursor to total alternator failure. Pull your  

alternator and get it checked at an alternator shop.

Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

 Antoine de Saint-Exupry

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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery

iflyhawaii2(at)yahoo.com
Guest

Posted: Mon May 29, 2006 8:59 am Post subject: Whining Radio

Wow.  I replaced the first Van's alternator at 10 hours due to amps jumping from + 32 amps to - 32 amps.  I would hate to just replace the second alternator.  Is there a way to test it on the plane?

Greg



		

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brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Mon May 29, 2006 10:19 am Post subject: Whining Radio

On May 29, 2006, at 9:56 AM, Greg Grigson wrote:



 	  Quote: 	
		   

 <iflyhawaii2(at)yahoo.com>



 Wow.  I replaced the first Van's alternator at 10 hours due to amps  

 jumping from + 32 amps to - 32 amps.  I would hate to just replace  

 the second alternator.  Is there a way to test it on the plane?


	


Yes. Put it under some kind of load and look at the output with an  

oscilloscope. Just connect the o-scope to the main distribution bus  

where the alternator B-lead connects. Do you have a 12VDC power jack  

for your GPS? That will work too and it is very easy to get to.



An alternator with all three phases working will have almost ripple- 

free output. An alternator that has lost a diode will lose the phase  

associated with that diode. The result will be greatly increased  

ripple in the bus voltage. (That ripple is what you are hearing in  

your comm radio.) Some automotive test meters have an "alternator  

test" scale that just measures the amount of ripple and gives you a  

"good/bad" reading which accomplishes essentially the same thing.



And if you have lost one diode it means that the load is being  

carried on only two of the three phases. This means that the  

remaining phases are now carrying 50% more load (each) for the same  

output from the alternator. That is why I said that losing a diode is  

a precursor to losing the whole alternator since most people don't  

think to reduce the load on the alternator by 1/3.



I wish I could give you better news. This is why it is probably  

cheaper to buy a really good alternator that is "hot rated" to run at  

its full rated output. Not having to fix it several times is worth a  

fair amount of money.



Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

 Antoine de Saint-Exupry

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mprather(at)spro.net
Guest

Posted: Mon May 29, 2006 12:34 pm Post subject: Whining Radio

Hey Brian,

Seems like you could use the AC setting on a DVM to see how much ripple

there is (if you don't have easy access to an Oscope)..

Also, I think diode packs are usually pretty easy to replace.  And for

MUCH less money than a completely new alternator will run you.

And finally, does anyone have any temperature data on this kind of

installation?  Does this airplane have a blast tube directed at the

alternator.  It might be as simple as adding one to the cooling baffle to

keep the temperature in check when you've got it running flat out. If the

alternator IS overloaded, and not dieing from some other cause, keeping it

cooler will be to its benefit.  When plumbing a blast tube into the

baffling, it might be worth considering adding it to the side (above one

of the valve covers) instead of at the back.  Pulling air from the side

may allow for a bit of 'inertial seperation' which may help keep the

alternator drier when flying through rain..

Regards,

Matt-

 	  Quote: 	

 <brian-yak(at)lloyd.com>

 On May 29, 2006, at 9:56 AM, Greg Grigson wrote:

> 

> <iflyhawaii2(at)yahoo.com>

>

> Wow.  I replaced the first Van's alternator at 10 hours due to amps

> jumping from + 32 amps to - 32 amps.  I would hate to just replace

> the second alternator.  Is there a way to test it on the plane?

 Yes. Put it under some kind of load and look at the output with an

 oscilloscope. Just connect the o-scope to the main distribution bus

 where the alternator B-lead connects. Do you have a 12VDC power jack

 for your GPS? That will work too and it is very easy to get to.

 An alternator with all three phases working will have almost ripple-

 free output. An alternator that has lost a diode will lose the phase

 associated with that diode. The result will be greatly increased

 ripple in the bus voltage. (That ripple is what you are hearing in

 your comm radio.) Some automotive test meters have an "alternator

 test" scale that just measures the amount of ripple and gives you a

 "good/bad" reading which accomplishes essentially the same thing.

 And if you have lost one diode it means that the load is being

 carried on only two of the three phases. This means that the

 remaining phases are now carrying 50% more load (each) for the same

 output from the alternator. That is why I said that losing a diode is

 a precursor to losing the whole alternator since most people don't

 think to reduce the load on the alternator by 1/3.

 I wish I could give you better news. This is why it is probably

 cheaper to buy a really good alternator that is "hot rated" to run at

 its full rated output. Not having to fix it several times is worth a

 fair amount of money.

 Brian Lloyd                         361 Catterline Way

 brian-yak AT lloyd DOT com          Folsom, CA 95630

 +1.916.367.2131 (voice)             +1.270.912.0788 (fax)

 I fly because it releases my mind from the tyranny of petty things . . .

  Antoine de Saint-Exupry

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Mon May 29, 2006 6:19 pm Post subject: Whining Radio

On May 29, 2006, at 1:29 PM, Matt Prather wrote:



 	  Quote: 	
		   

 <mprather(at)spro.net>



 Hey Brian,



 Seems like you could use the AC setting on a DVM to see how much  

 ripple

 there is (if you don't have easy access to an Oscope)..


	


That is possible but it must be an AC-only mode (cap coupled) and not  

measuring AC+DC.

 	  Quote: 	
		  

 Also, I think diode packs are usually pretty easy to replace.  And for

 MUCH less money than a completely new alternator will run you.


	


You can do that. The alternator shop can do that pretty quickly. Of  

course, the question is now why he has had TWO alternator failures.



Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

 Antoine de Saint-Exupry

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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