I confirm the exact same hum issue as Mike describes below. (Front panel power switch is off and there is an intermittent acoustic hum that can be heard) I own KPA500 #236. It's not a problem so long as it's not doing any damage. Lets see what the folks at Elecraft come up with after their investigation.
Frank - W6NEK ----- Original Message ----- From: "ai6ii" <ai...@att.net> To: <elecraft@mailman.qth.net> Sent: Monday, August 01, 2011 10:13 PM Subject: Re: [Elecraft] KPA 500 Hum >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 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
