Date: Wed, 03 Mar 2010 13:45:23 -0500
From: johndtate@post.com
Subject: [Amps] 120 cycle hum from Henry 2K-4
Update to the Henry Hum. Much of the hum was magnetic pickup and
moving things and better grounding solved that. It was another
operator that first said "That's 120 cycle hum". I don't think it was.
It was 60 cycle hum.
The Henry 2K-4 and other Henry amps use a filament choke wound on a
torroid. More than one Henry owner told me they solved their hum
problems with a rod based bifilar wound choke. RF Parts has them for
20 bucks. I replaced the stock choke with it and that solved the hum.
Maybe this will help others in the future.
73, John KX5JT
## This is amazing. Was the stock torroid wound in bifilar fashion??
## this makes no sense at all.. even if they were short on uh. The one
case of hum that I know about, was a local ham, who built a HB
2 x 3-500Z amp.. and wound his own fil xfmr, by re-winding the sec
of another xfmr. He ended up with too high a loaded V.... so he removed
some turns... from one side only! This of course left the CT OFFSET..
which of course will induce 60 hz hum.
## Was the hum audible on SSB... or just when using AM ??
later...... Jim VE7RF
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