[Elecraft] KPA500 code oscillator

[Ron D'Eau Claire]

Ouch! Time to call/e-mail support Joe. 

73 Ron AC7AC

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of W1GO
(Joe)
Sent: Sunday, October 23, 2016 5:45 PM
To: Ron D'Eau Claire
Cc: Elecraft Reflector
Subject: Re: [Elecraft] KPA500 code oscillator

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 <ron at cobi.biz> 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
> 

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