My KPA500 now seems to have the hummms. It comes and goes whether the unit is on or off. It does go away when you turn off the rear switch.
I noticed someone changed the tap and that appeared to fix the hum. I am running the amp on 110V. My actual wall voltage is 119V. I did not notice this at all while I was at our Montana home over the summer. Mike W0MU -- J6/W0MU November 21 - December 1 2011 CQ WW DX CW W0MU-1 CC Cluster w0mu.net ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html

