[Elecraft] K3 3051 audio buzz in chassis on SSB

[David Cutter]

Full marks for your investigation, Craig.  Sounds like the winding tension 
was set too high and the core bit through the enamel.  That will be covered 
by the Elecraft guarantee.

David
G3UNA


----- Original Message ----- 
From: "Craig" <vk3he at yahoo.com>
To: <elecraft at mailman.qth.net>
Sent: Sunday, July 05, 2009 1:05 AM
Subject: [Elecraft] K3 3051 audio buzz in chassis on SSB


>
> Hi Paul
>
> I had a similar problem which drove me nuts.
>
> I pulled the K3 apart to try and find this problem and  tightening every 
> screw in the
> re-assembly process. The  problem persisted however. This  buzz was 
> following my SSB
> modulation  with perfect timing.
>
> I used a stethoscope and found that the buzz was  coming from a small area 
> where the
> SWR/power meter directional coupler was situated. The problem turned out 
> to be one of
> the directional couplers transformers which was arcing to the ferrite 
> core.
>
> At first sight the transformer looked perfect, however I could clearly 
> hear the buzz in the
> stethoscope. I replaced the ferrite transformer and the buzz went away. 
> When I examined
> this   transformer,  the arcing signs were very obvious under the enamel 
> wire facing the
> core.
>
> The directional coupler transformers are very small and its a tricky job 
> getting it  back in
> place. Ideally this transformer should have better insulation, however 
> there is not much
> room on the  core for extra insulation.
>
>
> 73
> Craig
>
>
>
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