K3 3051 audio buzz in chassis on SSB

[Craig-89]

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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[Tom-N2YTF]

Craig,

Any chance you could post or email me a few pictures? Also, what transformer did you use to replace the stock one?

Thanks!

Tom-N2YTF
email is n2ytf at the standard arrl email address.

Craig-89 wrote

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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[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" <[hidden email]>
To: <[hidden email]>
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
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html 

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