There is KPA500 buzz (normal), and KPA500 BUZZ (abnormal). I own two. KPA Numero Uno was bought way back when, when the kits were first available. When I first built it, it buzzed something akin to to your teeth clacking when you notice a full-grown T. Rex is standing next to you. At that time, many were complaining about KPA500 buzz, but one must understand that some would complain that their K3 did not come with the case stuffed with Krugerands. A call to Support convinced them it was really loud. They sent me an updated bolt, washer, and spacer set. I very carefully repositioned the transformer, and torqued the bolt to factory spec. Several times. No buzz then, no buzz now that I can hear. I do now have an LP-100A sitting on the top left forward of the cabinet. A perfect fit. Perhaps that is a dampner, who knows.
KPA500 Numero Two-o was bought this year, is factory-built, and has a very slight audible buzz on cw. These amps have compact, toroidal, linear transformers that produce a little buzz. If it ever rises to an annoying level, I would: 1) Turn off the amp using the front-panel switch to drain the filter caps and let the fan run all the way down. 2) Turn off the rear-panel switch. 3) Unlug the amp from A/C. 4. Remove the top cover as shown in the manual. 5) Using a very strong light, see if the transformer is touching the cabinet. 6) If so, you can SLIGHTLY. loosen the bolt (PAY ATTENTION TO THE TIGHTNESS OF THE BOLT IF YOU DO NOT HAVE A TORQUE WRENCH), and very, very carefully adjust the transformer so it is a hair away from the cabinet on all sides. 7) Reverse the steps. Repeat if necessary. OR Call Support. OR wear headphones. OR Fuggedaboutit. NOTE: You can indeed make it worse. The reason you are probably hearing it for the first time is that all amps I have owned with linear supplies also buzz, but the constant fan masks it. 73 Eric WD6DBM On Sat, May 29, 2021, 5:57 PM k2qo <[email protected]> wrote: > After much searching, this 2.4 year old thread is the only info I can find > on > this issue. I bought a factory built KPA500 a few months ago and mine > buzzes > on CW key down. Af first I thought maybe this is normal as I never owned an > HF amp. Now I think it is a problem. > > Any know how to fix this? I can shoot a short movie if that helps. > > 73, > Mark K2QO > > > > -- > Sent from: http://elecraft.365791.n2.nabble.com/ > ______________________________________________________________ > 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]
