Hi Jim, I had a bad hum from my KPA500 kit, an early model. Elecraft sent me a new center bolt that was only threaded on the end--the original bolt had threads all along the shaft. Also an additional pad.
Assuming you assembled it all correctly, try these two things: If you have a torque wrench, tighten the bolt to the exact spec. If you don't have one, try slightly tightening or even loosening the bolt. Second, make sure the transformer is exactly centered on the bolt and not touching any of the sheet metal, including the side panel. Use a strong flashlight to check it with the top removed. UNPLUG THE AMP FIRST! Mine has been hum-free for years, after the tweaking. 73 Eric WD6DBM On Mon, Oct 19, 2020, 5:00 PM Jim Spikes N4KH <jimn...@gmail.com> wrote: > Looking for details from anyone who resolved issues with excessive > transformer hum during transmit on a KPA-500. > > > > I have a hum mitigation application note sent from Elecraft tech support. > But the procedure recommended is pretty involved - removing front/side > panels, un-plugging connections, removing the transformer, changing > positions of the rubber discs, and putting it back together. Possibly more > than once, depending on the results. > > > > There is a risk of breaking something, and I'm not sure its going to solve > the problem if I'm successful. This is a new out of the box KPA500 kit. > > > > If anybody has any lessons learned I would appreciate hearing them. > > > > Jim, N4KH > > ______________________________________________________________ > 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 > Message delivered to norrislawfi...@gmail.com > ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
