Al, Quick follow-up on the KPA500 with the very loud buzzing transformer … after hours of disassembling, reassembling, tightening, etc., I couldn’t correct the problem and sent the unit back to the mother ship. The transformer had a problem and was replaced. I have heard from others that they were similarly told of a problem with transformers that would require replacement. My unit is now wonderfully quiet.
My unit was a kit, but it makes me wonder if the “burn-in” of assembled units is simply an idle current test or if the unit it tested under load at different modes; my unit was quiet on SSB but ferociously loud on CW (even at 5W drive). It seems that would be pretty easy to detect in an assembled unit; kits are a whole other story. In any event, aside for the $80+ it cost me to ship the unit back, all is well … and quiet. Joe W1GO > On Oct 23, 2016, at 5:46 PM, W1GO (Joe) <[email protected]> wrote: > > > Hi all, > > Finished assembly of KPA500 and a little surprised at the magnitude of hum / > buzz during CW (no real issue on SSB); I've read about it but was surprised > at just how pronounced it is. I could use the KPA500 as a code oscillator > for practice; no need to keep monitor turned on. I've read most of the > historical dialogue regarding methods to minimize "the buzz": use yellow wire > tap, keep wires from touching chassis, make sure everything (including > transformer) is good and tight, etc. all those things are done with little > positive impact. I'm running off well regulated 240 VAC. > > I just wonder if anyone has any other "secrets" they might share. My code > proficiency is not great, at this point, and having the KPA500 groan in > response to my keying is somewhat distracting; even with headphones when > monitor is turned up higher than usual. > > Best regards, > > Joe > W1GO > ______________________________________________________________ > 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 > Message delivered to [email protected] ______________________________________________________________ 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 Message delivered to [email protected]
