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 <johnn...@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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