Thanks, Ron. Did all suggested and ensured every screw and bolt tightened. Reseated transformer and really tightened down. Unfortunately, same hum on CW; even with less than 10W drive.
Back to the drawing board. Thank you, Joe W1GO > On Oct 23, 2016, at 5:56 PM, Ron D'Eau Claire <[email protected]> wrote: > > When you remove the KPA500 top cover, the Z-bracket is the metal bracket > running from the front to back panels dividing the inside into the power > supply (with the big transformer) and RF sections. > > The Z-bracket attaches to the front and back panels, the bottom cover and to > the top. Make sure you got all the screws tight. > > Also, be sure you installed the transformer correctly, including the rubber > disk between the transformer and the bottom cover and you have the bumpers > in place where the transformer rests against edge. Be sure the Bellevue > washer is installed right side up. That's the washer under the nut holding > the transformer in place. As the text explained, it is very slightly conical > and must be installed so the center hole of the washer is slightly higher > than the edges. Put it on the desk and tap on the edges of the washer with a > pencil. If it rocks a bit, it is upside. If it is right side up, it will sit > still. Be sure it is installed right side up. > > Finally, tighten the nut on the Bellevue washer a bit more. If you have a > torque wrench available, it should be set to 55 in/lbs but it is not real > critical. As the text says, run the washer down onto the Bellevue washer, > and then tighten one or two turns further. IF needed add a bit more to quiet > it! > > My KPA500 hums under full load, but not loudly - about as loud as my Astron > power supply under full load. If anything is "buzzing" it is certainly a > loose fastener somewhere. > > 73, Ron AC7AC > ______________________________________________________________ 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]
