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KPA500 Hum

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John_N1JM

KPA500 Hum

I don't use my KPA500 a lot, but I just noticed with only the back switch on
I can hear a hum coming from the amp. It disappears of course when I turn
the switch off. Is this normal?

73, John N1JM

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Bob McGraw - K4TAX

Re: KPA500 Hum

Yes it is normal to hear a slight hum when the Mains switch is on. Also
the left side may be slightly warm.    When the Mains switch is on, the
low voltage power supply is on.    This supply is for the logic and
processing.

See the IMPORTANT section on page 14 of the manual for further details.

Wonderful amp.   Love mine.

73

Bob, K4TAX

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John_N1JM

Re: KPA500 Hum

Thanks Bob. Yes great amp.
73, John N1JM

Bob McGraw - K4TAX wrote

> Yes it is normal to hear a slight hum when the Mains switch is on. Also
> the left side may be slightly warm.    When the Mains switch is on, the
> low voltage power supply is on.    This supply is for the logic and
> processing.
>
> See the IMPORTANT section on page 14 of the manual for further details.
>
> Wonderful amp.   Love mine.
>
> 73
>
>
>
>
>
>
>
> Bob, K4TAX
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Elecraft@.qth

>
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> lists+1215531472858-365791@.nabble

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Elecraft mailing list

Re: KPA500 Hum

John,

When my KPA500 hums, I assume it is a power quality problem.
It only hums when a curling iron or coffee maker, both of which are on different circuits, are in operation.

--mark/ae0mm

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Friday, January 4, 2019 8:14 AM, John_N1JM <[hidden email]> wrote:

> Thanks Bob. Yes great amp.
> 73, John N1JM
>
> Bob McGraw - K4TAX wrote
>
> > Yes it is normal to hear a slight hum when the Mains switch is on. Also
> > the left side may be slightly warm.    When the Mains switch is on, the
> > low voltage power supply is on.    This supply is for the logic and
> > processing.
> > See the IMPORTANT section on page 14 of the manual for further details.
> > Wonderful amp.   Love mine.
> > 73
> > Bob, K4TAX
> >
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:
>
> > Elecraft@.qth
>
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> > Message delivered to
>
> > lists+1215531472858-365791@.nabble
>
> --
>
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Bob McGraw - K4TAX

Re: KPA500 Hum

Mark et al:

Your description raises a bit of concern. Not with the amplifier but
with your power distribution in your home / QTH.

First I'll presume you are running the amp on 120V and not 240V.   Thus
being so, as the coffee maker comes on or curling iron comes on the
Neutral current changes. The fact they are on separate circuits is one
point but they thus share the same neutral.   If your Neutral is
"floating" due to poor conductivity or corroded connections this will
cause distortion of the 60 Hz sine wave.   This distortion is always
higher in frequency and is multiples of the 60 Hz signal.   These
distortion products can cause a transformer to "talk" a bit.

If not yourself qualified, I would obtain a qualified electrician or
consult with your power company about the issue.   Conclusion: Something
isn't right and should be corrected.     I'm sure others may have
further ideas or experiences with this phenomenon.

73

Bob, K4TAX

On 1/4/2019 9:27 AM, AE0MM via Elecraft wrote:

> John,
>
> When my KPA500 hums, I assume it is a power quality problem.
> It only hums when a curling iron or coffee maker, both of which are on different circuits, are in operation.
>
>
> --mark/ae0mm
>
>
> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Friday, January 4, 2019 8:14 AM, John_N1JM <[hidden email]> wrote:
>
>> Thanks Bob. Yes great amp.
>> 73, John N1JM
>>
>> Bob McGraw - K4TAX wrote
>>
>>> Yes it is normal to hear a slight hum when the Mains switch is on. Also
>>> the left side may be slightly warm.    When the Mains switch is on, the
>>> low voltage power supply is on.    This supply is for the logic and
>>> processing.
>>> See the IMPORTANT section on page 14 of the manual for further details.
>>> Wonderful amp.   Love mine.
>>> 73
>>> Bob, K4TAX
>>>
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:
>>> Elecraft@.qth
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>> Message delivered to
>>> lists+1215531472858-365791@.nabble
>> --
>>
>> Sent from: http://elecraft.365791.n2.nabble.com/
>>
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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Jim Brown-10

Re: KPA500 Hum

On 1/4/2019 10:52 AM, Bob McGraw K4TAX wrote:

> Mark et al:
>
> Your description raises a bit of concern. Not with the amplifier but
> with your power distribution in your home / QTH.
>
> Yes. This is the symptom of one or more mis-wired outlets, or of an
> extra bond between neutral and ground somewhere in your home. This
> used to be common practice at large appliances. I would start by
> buying and using a good outlet tester, which will check the wiring at
> every outlet in your home.
>
>
> First I'll presume you are running the amp on 120V and not 240V. Thus
> being so, as the coffee maker comes on or curling iron comes on the
> Neutral current changes. The fact they are on separate circuits is
> one point but they thus share the same neutral. If your Neutral is
> "floating" due to poor conductivity or corroded connections this will
> cause distortion of the 60 Hz sine wave.

I think you mean neutral coming from the power company, not within the
home.

> This distortion is always higher in frequency and is multiples of the
> 60 Hz signal.

There is ALWAYS significant distortion of the AC power waveform that it
is NOT the result of any sort of wiring problem. Rather, it is caused by
all the rectifier-filter power supplies in virtually every piece of
electronics in our homes and businesses. Line current flows mostly at
the positive and negative peaks of the AC cycle to recharge the filter
capacitors, resulting IR drop only during those peaks. The peaks are
rounded off, and the current is a series of pulses. There's a discussion
of this beginning with slide 55 of this talk on Power, Grounding, and
Bonding for Ham Radio. http://k9yc.com/GroundingAndAudio.pdf

73, Jim K9YC

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Nr4c

Re: KPA500 Hum

In reply to this post by John_N1JM

Prob. The front switch is a “soft switch”. Wakes up the amp from a nap.

Sent from my iPhone
...nr4c. bill

> On Jan 4, 2019, at 12:57 AM, John_N1JM <[hidden email]> wrote:
>
> I don't use my KPA500 a lot, but I just noticed with only the back switch on
> I can hear a hum coming from the amp. It disappears of course when I turn
> the switch off. Is this normal?
>
> 73, John N1JM
>
>
>
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
> ______________________________________________________________
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