My KPA500 (that I built about a year ago) buzzes in the same way as Michael's. My transformer is hard against the rubber buffers, the double-rubber pads are properly in place, and the bolt is nicely torqued down. I'd be interested in hearing any ideas to mitigate this issue also.
73, Dave AD6A -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Michael Blake Sent: Thursday, January 25, 2018 5:50 PM To: Elecraft Mailing List <elecraft@mailman.qth.net> Subject: [Elecraft] KPA500 cabinet buzz I just built my KPA500 today and on the air reports were good. 20watts Drive seemed right for about 500 watt peaks. After running it for about an hour I shut down to clean up the kit building mess and when I returned later I was hearing a loud 60 cycle mechanical buzz from the left side of the cabinet when in operation. The buzz would vary from very light when keyed with no drive to quite loud when putting out 500 watts CW. I had not noticed any noise earlier but I was wearing Bose noise cancelling headphones as I normally do. The voltage looks normal under load and the output power is 500 watts with a little over 20 watts drive. I removed the top cover, loosened the transformer mounting bolt a bit, turned it up on its left side to make sure the transformer was resting against the two bumpers and retightened the mounting screw per the instructions. This did not result in any change in the mechanical vibration. Any suggestions? Michael Blake k9...@mac.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 d...@ad6a.com --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ______________________________________________________________ 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
