KPA500 Hum

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KPA500 Hum

w0mu
My KPA500 now seems to have the hummms.  It comes and goes whether the
unit is on or off.  It does go away when you turn off the rear switch.

I noticed someone changed the tap and that appeared to fix the hum.

I am running the amp on 110V.  My actual wall voltage is 119V.

I did not notice this at all while I was at our Montana home over the
summer.

Mike W0MU

--
J6/W0MU November 21 - December 1 2011 CQ WW DX CW
W0MU-1 CC Cluster w0mu.net

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Re: KPA500 Hum

Eric Swartz - WA6HHQ, Elecraft
Administrator
Hi Mike,

This doesn't sound unusual.

There is also a normal amount of 'resting' idle low level transformer
hum, which varies with line voltage and frequency.  Also, when the rear
switch is on, the transformer primary is active even when the front
switch is off ( but the output windings are disconnected from the amp.)  
the front switch is more like a stand-by - active switch.

73, Eric   WA6HHQ

---
www.elecraft.com


On 9/26/2011 11:49 AM, Ron D'Eau Claire wrote:

> What you are describing is very unusual, Mike.
>
> Typically, one will hear some hum from the transformer with  the "key down"
> (full 500 watt carrier). It is most pronounced when using the green
> transformer tap (lowest line voltage input). Normally there is no hum with
> the KPA500 off, or when running the KPA500 at low duty-cycle loads such as
> SSB, even at full peak power output.
>
> I'd drop a line to the elecraft support reflector and see what the
> Ele-guru's say.
>
> 73,
>
> Ron AC7AC
>
> -----Original Message-----
>
> My KPA500 now seems to have the hummms.  It comes and goes whether the
> unit is on or off.  It does go away when you turn off the rear switch.
>
> I noticed someone changed the tap and that appeared to fix the hum.
>
> I am running the amp on 110V.  My actual wall voltage is 119V.
>
> I did not notice this at all while I was at our Montana home over the
> summer.
>
> Mike W0MU
>
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Re: KPA500 Hum

w0mu
Ok.  I just never heard it before.  I did recall others mentioning
this.  It is not loud.  The amp works great.

J6/W0MU November 21 - December 1 2011 CQ WW DX CW
W0MU-1 CC Cluster w0mu.net


On 9/26/2011 1:07 PM, Eric Swartz - WA6HHQ, Elecraft wrote:

> Hi Mike,
>
> This doesn't sound unusual.
>
> There is also a normal amount of 'resting' idle low level transformer
> hum, which varies with line voltage and frequency.  Also, when the
> rear switch is on, the transformer primary is active even when the
> front switch is off ( but the output windings are disconnected from
> the amp.)  the front switch is more like a stand-by - active switch.
>
> 73, Eric   WA6HHQ
>
> ---
> www.elecraft.com
>
>
> On 9/26/2011 11:49 AM, Ron D'Eau Claire wrote:
>> What you are describing is very unusual, Mike.
>>
>> Typically, one will hear some hum from the transformer with  the "key
>> down"
>> (full 500 watt carrier). It is most pronounced when using the green
>> transformer tap (lowest line voltage input). Normally there is no hum
>> with
>> the KPA500 off, or when running the KPA500 at low duty-cycle loads
>> such as
>> SSB, even at full peak power output.
>>
>> I'd drop a line to the elecraft support reflector and see what the
>> Ele-guru's say.
>>
>> 73,
>>
>> Ron AC7AC
>>
>> -----Original Message-----
>>
>> My KPA500 now seems to have the hummms.  It comes and goes whether the
>> unit is on or off.  It does go away when you turn off the rear switch.
>>
>> I noticed someone changed the tap and that appeared to fix the hum.
>>
>> I am running the amp on 110V.  My actual wall voltage is 119V.
>>
>> I did not notice this at all while I was at our Montana home over the
>> summer.
>>
>> Mike W0MU
>>
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Re: KPA500 Hum

Leigh L. Klotz Jr WA5ZNU
Administrator
In reply to this post by Eric Swartz - WA6HHQ, Elecraft
Twice mine has hummed loudly enough (always when off from the front, on from the rear) that I looked for the noise, and unplugged it.  I guess perhaps it's related to line voltage, which changes.  I will monitor line voltage with my KILL-A-WATT meter and see if I can correlate it.

Leigh/WA5ZNU
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Re: KPA500 Hum

gm3sek
In reply to this post by Eric Swartz - WA6HHQ, Elecraft
Ron D'Eau Claire wrote:
>Mike, I certainly concur with Eric's observation. What I thought was
>very unusual was that you said that the hum would come and go, which I
>presume happens when you aren't doing anything at the amp.
>

Hum that comes and goes for no apparent reason might be caused by some
other large electrical appliance distorting the AC supply waveform - for
example, an electric motor with a chopper-controlled Variable Speed
Drive.

Although the 60/50Hz hum level from the KPA500 transformer is normally
very low, a sudden increase in the higher harmonics could be quite
noticeable.


--

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek
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Re: KPA500 Hum

Arie Kleingeld PA3A-2
Hope there comes a hardware mod to obtain minimum hum.

73
Arie PA3A

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KPA500 Hum

Johnny Siu
Hello Arie,
 
There has been additional new hardwares in the installation of the transformer as in the latest KPA500 kit construction manual.
 
I have solved the hum problem by trying another transformer tap and installing the new hardwares.

TNX & 73,


Johnny VR2XMC

從︰ Arie Kleingeld PA3A <[hidden email]>
收件人︰ [hidden email]
傳送日期︰ 2011年09月27日 (週二) 9:23 PM
主題︰ Re: [Elecraft] KPA500 Hum

Hope there comes a hardware mod to obtain minimum hum.

73
Arie PA3A

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