My KPA500 #274 worked fine with the yellow wire installed, but the voltage was a bit low (56-year old house) and output on 6M was also a tad low. I wired it for 220v. Since I use it for meteor scatter on 6m, I really wanted full output. But when I switched to the red wire, I got a terrible buzz. I don't mean a slight buzz, I mean a buzz on the order of an arc welder running at full tilt. A buzz that was louder than when the pole pig across the street caught fire. A buzz far too loud to be tolerated in a nice, quiet, Elecraft-equipped shack. I tried repositioning the transformer a number of times to no avail. I finally contacted Gary at Elecraft support, and working with him got the problem solved. Here's what I did: 1) Replaced the transformer hold-down bolt that was threaded only at the top with a bolt that was threaded all the way down. I installed this according to the new procedure in the KPA500 assembly manual (this is now shipped with all KPA500s). 2) I zip-tied together a number of the wires so that they were not contacting the transformer or the top of the case any more than was necessary. 3) I used a torque wrench to install the transformer to the correct spec in the manual. I'm not sure what fixed it, but the buzz is now down to a very slight, almost unnoticeable level. I have silent QRO on CW. Luxury. I offer this for anyone with an early KPA500 with a loud buzzing problem. When this thread was active there seemed to be some confusion about what was a normal buzzing level. Wayne stated that some buzz was normal, but I am sure that others experienced this extremely loud buzz that is not normal. I never saw a resolution of this thread, so if I missed it my apologies. 73, Eric WD6DBM ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected]
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