[Elecraft] KPA500 cabinet buzz

[Chris Hallinan]

Mine is about 2 months old and has buzzed during key-down since I first
powered it up.  Just figured it was that giant toroidal transforming doing
its thing.

Chris K1AY

On Thu, Jan 25, 2018 at 9:46 PM, Dave AD6A <dave at ad6a.com> wrote:

> My KPA500 (that I built about a year ago) buzzes in the same way as
> Michael's.
> My transformer is hard against the rubber buffers, the double-rubber pads
> are properly in place, and the bolt is nicely torqued down. I'd be
> interested in hearing any ideas to mitigate this issue also.
>
> 73, Dave AD6A
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Michael Blake
> Sent: Thursday, January 25, 2018 5:50 PM
> To: Elecraft Mailing List <elecraft at mailman.qth.net>
> Subject: [Elecraft] KPA500 cabinet buzz
>
> I just built my KPA500 today and on the air reports were good. 20watts
> Drive
> seemed right for about 500 watt peaks. After running it for about an hour I
> shut down to clean up the kit building mess and when I returned later I was
> hearing a loud 60 cycle mechanical buzz from the left side of the cabinet
> when in operation. The buzz would vary from very light when keyed with no
> drive to quite loud when putting out 500 watts CW. I had not noticed any
> noise earlier but I was wearing Bose noise cancelling headphones as I
> normally do.
>
> The voltage looks normal under load and the output power is 500 watts with
> a
> little over 20 watts drive.
>
> I removed the top cover, loosened the transformer mounting bolt a bit,
> turned it up on its left side to make sure the transformer was resting
> against the two bumpers and retightened the mounting screw per the
> instructions.  This did not result in any change in the mechanical
> vibration.
>
> Any suggestions?
>
> Michael Blake
> k9jri at mac.com
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message
> delivered to dave at ad6a.com
>
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to challinan at gmail.com
>



-- 
Life is like Linux - it never stands still.