[Elecraft] KPA500 Noise While Off

[Richard Wade]

Yesterday I heard a faint "hum" in my shack but all of my gear was off.  It
sounded like possibly a fan running or power supply noise.  I did a very
scientific test of the sound source by putting my ear to each piece of
equipment in my shack and soon found that the noise was coming from my
KPA500!  The amplifier was off but was still connected to the shack ac
power.  I then removed the power cord from the KPA500 and the noise
disappeared.  Does anyone have any idea how this could  happen?

By way of further background, I have been dealing with QRN from a recently
installed solar system.  I have traced the source of that noise to the
solar system by confirming that the QRN goes away when the solar system is
turned off while running my K3s on battery power.

If I had to venture a guess, I would say that somehow the unpowered KPA500
was picking up noise on the shack wiring.  Very strange. Is that possible??

Dick, WM6G