[Elecraft] KPA500 Hum

[Bob McGraw K4TAX]

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 <johnn1jm at gmail.com> 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
>>>
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