[Elecraft] [KPA500] incredible hum from PA

[Ron D'Eau Claire]

Joe might be right but contact Tech Support first. The transformer is held in place with a single large bolt through the center (it is a torodial transformer). If that bolt is not tightened properly the magnetic field will produce a huge vibration. Even if you did not build the amp from the kit, it's a pretty simple job to tighten that bolt. Tech Support can lead you through the process. It is also described in the kit assembly manual available on the Elecraft web site here;
http://www.elecraft.com/manual/E740149%20KPA500%20Kit%20Assembly%20Manual%20Rev%20F6.pdf

See pages 36 and 37. 

73, Ron AC7AC

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of W1GO (Joe)
Sent: Monday, December 19, 2016 6:19 PM
To: kevino z
Cc: Elecraft Reflector
Subject: Re: [Elecraft] [KPA500] incredible hum from PA

Kevin,

Yes.  had the problem.  Crazy loud hum / buzz.  Bad transformer I was told.  All quiet on the eastern front now.  If it is a bad transformer it can be fixed but you’ll have to eat the shipping charge.

Joe
W1GO

> On Dec 19, 2016, at 9:10 PM, kevino z <z_kevino at hotmail.com> wrote:
> 
> Just got my KPA500 and KAT500. I hooked the PA up to 240v (well, my Mains are 248v), so I made sure the assembled PA has the yellow transformer tap, from the factory.
> When I engage the amp, there is a crazy buzz. I use a KPA500 at work, but it is on 120v and I never hear this buzz. Before I swap fuses, and switch over to 120v to test, does anyone else have this issue?
> The KPA500 is hooked up to a KX3/KXPA100 combo, just in case someone would ask.
> Thanks
> -Kevin (KK4YEL)
> 
> 
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