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Electronics International MVP-50 Display

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N4ZQ(at)comcast.net
Guest

Posted: Thu Oct 15, 2009 5:16 am Post subject: Electronics International MVP-50 Display

I'm currently struggling with a display issue. The MVP-50 has a  

photocell which dims the display under low light conditions. With the  

unit installed in the panel and audio fed to an unswitched input on  

the PS Engineering PMA4000 audio panel, there is a distinct hum in the  

headset when the display is fully dimmed. The hum gradually fades to  

nothing with normal daylight conditions. The display can be set to dim  

automatically or manually through an external dimmer pot and I hear  

the same result either way. I called the folks at EI in Oregon and  

with the phone held near the speaker in the cockpit, they were able to  

hear the hum!



The initial suspect was a ground loop problem but this was ruled out  

because when I removed the display and powered it up on the bench and  

connected my headset directly to the audio output, I was able to  

reproduce the same hum. Unfortunately, I don't have a scope to see  

what I hear.



EI requested that I return the unit since they were convinced the  

problem was internal to the display.

Now here's the weird part. Their techs were not able to duplicate what  

I heard AND what they heard over the phone.

They say the display is operating normally and I got it back  

yesterday. My first action was to set it back up on the bench and Low  

and Behold, the hum is still there when the display is dimmed.



Any suggestions here would be most helpful since I'm beginning to  

think that electrons behave differently on the west coast vs the east  

coast!



Angier Ames

N4ZQ

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Oct 15, 2009 5:51 am Post subject: Electronics International MVP-50 Display

At 08:11 AM 10/15/2009, you wrote:

 	  Quote: 	
		  




	


<snip>

 	  Quote: 	
		  Any suggestions here would be most helpful since I'm beginning to

think that electrons behave differently on the west coast vs the east

coast!


	


   Until you identify the propagation mode, a solution

   is not easy to deduce. It seems most likely that

   the noise is conducted on the 14v supply lines.

   Try operating either or both devices from separate

   12v sources (preferably batteries) and see what

   combination, if any eliminates the noise.



        Bob . . .



         ---------------------------------------

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

         ---------------------------------------

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marcausman

Joined: 08 Feb 2007
Posts: 70

Posted: Fri Oct 16, 2009 6:59 am Post subject: Re: Electronics International MVP-50 Display

Can you hear the noise while in cruise flight? As far as I can tell, many planes have some sort of noise from strobes, autopilot servos, alternator whine, etc. but once in flight the noise is really not bothersome. 



So from a pragmatic perspective, if it's not bothering you in flight then maybe it's acceptable.



Just another thought to ponder...

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_________________
Marc Ausman
http://www.verticalpower.com "Move up to a modern electrical system"
RV-7 IO-390 Flying

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