[Elecraft] KPA 500 Hum

[W6NEK]

No sooner do I make a post regarding the KPA500 hum issue (below) then I 
read a post from Eric (WA6HHQ) saying that the hum is normal for the design 
and not a problem.  Thanks for the feedback Eric.  Now that I know it normal 
I'll not worry that I did something wrong when I assembled the amp. ;-)

Frank - W6NEK

----- Original Message ----- 
From: "W6NEK" <w6nek at socal.rr.com>
To: <elecraft at mailman.qth.net>
Sent: Wednesday, August 03, 2011 8:59 AM
Subject: Re: [Elecraft] KPA 500 Hum


>I confirm the exact same hum issue as Mike describes below.
> (Front panel power switch is off and there is an intermittent acoustic hum
> that can be heard)
> I own KPA500 #236.  It's not a problem so long as it's not doing any 
> damage.
> Lets see what the folks at Elecraft come up with after their 
> investigation.
>
> Frank - W6NEK
>
> ----- Original Message ----- 
> From: "ai6ii" <ai6ii at att.net>
> To: <elecraft at mailman.qth.net>
> Sent: Monday, August 01, 2011 10:13 PM
> Subject: Re: [Elecraft] KPA 500 Hum
>
>
>>I too have noticed a hum emanating from the KPA500 (#26), but the
>> circumstances are a bit strange. The hum comes sometimes when the KPA500
>> is
>> off. By that I mean it is powered down (front panel power switch is
>> off..no
>> leds are lit), but not removed from the AC outlet. If I flip the rocker
>> switch on the back of the rig, the hum disappears, which would make sense
>> because no AC would be coming into the box, right?
>>
>> But if I leave the back rocker switch on and use only the push button
>> switch
>> on the front panel to turn the amp on and off, occasionally I hear a hum
>> when it is 'off'. And I do mean only occasionally. I have noticed it only
>> a
>> few times and I have been using the amp almost daily for the last month
>> and
>> a half. When it has occurred, it has been eliminated by switching off the
>> rocker switch in the back.
>>
>> It is not really a problem for me, but I thought it might be additional
>> information for Wayne et al.
>>
>> ..mike AI6II
>
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