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[Amps] GS-35 being cantankerous

To: <amps@contesting.com>
Subject: [Amps] GS-35 being cantankerous
From: steve at oakcom.com (Steve Maki)
Date: Mon Jun 23 08:19:04 2003
K8GM asked me to post this plea for help...

He is playing around with a GS-35, and so far hasn't been able
to be happy.

The symptom is as follows:

As the drive is increased, at some relatively random point,
the tube makes a single pop - he says it sounds like someone
snapping their fingers. He sees no abnormal meter indication
or change in output - in fact, the amp continues to operate
normally. There's only one small problem - when the pop happens,
it distorts the plate choke windings. They sort of get all 
bunched up as if some large force tried to slide them along
the form with enough force to stretch the wire and cause over-
lapping. No fuse blows, and except for this occasional pop,
the amp works great.

His supply is c. 3500V, and he's tried a couple of different
chokes, both commercial and homebrew. It appears to be strictly
a tube issue, rather than associated circuitry, but in our
preliminary web search haven't come up with references to this
problem.

What's happening here? Does the GS-35 need some kind of magic
pre-conditioning? He has idled the tube at full voltage for a
few hours, but that didn't do the trick.

Any help would be greatly appreciated.

73,
Steve K8LX
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