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KPA 500 Hum

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Klaus Koppendorfer

KPA 500 Hum

Last week i assembled the kpa500 of oe6rdd
when we transmit we hear a realy loud hum (50hz) in the rythm of the cw signals

i have compared this with my own kpa-500 and there is no hum
i have tried to loosen the big srew which holds the tranformer with no result

any ideas ??

73
Klaus
OE6KYG
KX1 244
K2 1331
K3 115

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N5GE

Re: KPA 500 Hum

Klaus,

Are you sure it is the KPA500?

My computer speakers in the shack will hum when using any of my HF amplifiers on
CW.

73,
Tom
Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member

On Mon, 1 Aug 2011 07:33:05 +0000, Klaus Koppendorfer <[hidden email]> wrote:

>
>Last week i assembled the kpa500 of oe6rdd
>when we transmit we hear a realy loud hum (50hz) in the rythm of the cw signals
>
>i have compared this with my own kpa-500 and there is no hum
>i have tried to loosen the big srew which holds the tranformer with no result
>
>any ideas ??
>
>73
>Klaus
>OE6KYG
>KX1 244
>K2 1331
>K3 115
>
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html

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Amateur Radio Operator N5GE

Lothar Sack-2

Re: KPA 500 Hum

In reply to this post by Klaus Koppendorfer

The same hum here since I changed to the *RED TAP (211 to 230V).*
I had _no hum with the YELLOW TAP (231 to 250 V)_. But then I had less
than 60V with full power.
The hum is coming out of the KPA500.
What to do?
Lothar, DJ8EW
K3 1300 + KPA500 229

Am 01.08.2011 09:33, schrieb Klaus Koppendorfer:

> Last week i assembled the kpa500 of oe6rdd
> when we transmit we hear a realy loud hum (50hz) in the rythm of the cw signals
>
> i have compared this with my own kpa-500 and there is no hum
> i have tried to loosen the big srew which holds the tranformer with no result
>
> any ideas ??
>
> 73
> Klaus
> OE6KYG
> KX1 244
> K2 1331
> K3 115
>

wayne burdick

Re: KPA 500 Hum

Administrator

We're looking into this.

73,
Wayne
N6KR

On Aug 1, 2011, at 3:11 PM, Lothar Sack wrote:

> The same hum here since I changed to the *RED TAP (211 to 230V).*
> I had _no hum with the YELLOW TAP (231 to 250 V)_. But then I had less
> than 60V with full power.
> The hum is coming out of the KPA500.
> What to do?
> Lothar, DJ8EW
> K3 1300 + KPA500 229
>
> Am 01.08.2011 09:33, schrieb Klaus Koppendorfer:
>> Last week i assembled the kpa500 of oe6rdd
>> when we transmit we hear a realy loud hum (50hz) in the rythm of
>> the cw signals
>>
>> i have compared this with my own kpa-500 and there is no hum
>> i have tried to loosen the big srew which holds the tranformer with
>> no result
>>
>> any ideas ??
>>
>> 73
>> Klaus
>> OE6KYG
>> KX1 244
>> K2 1331
>> K3 115
>>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

mike

Re: 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

W6NEK

Re: 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" <[hidden email]>
To: <[hidden email]>
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

W6NEK

Re: KPA 500 Hum

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" <[hidden email]>
To: <[hidden email]>
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" <[hidden email]>
> To: <[hidden email]>
> 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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>
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