[Elecraft] KPA 500 Hum

[ai6ii]

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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