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Re: [Amps] GS35B Idle current increasing

To: amps <amps@contesting.com>
Subject: Re: [Amps] GS35B Idle current increasing
From: Ron Youvan <ka4inm@gmail.com>
Reply-to: ka4inm@gmail.com
Date: Sat, 10 Mar 2018 13:06:55 -0500
List-post: <mailto:amps@contesting.com>
  Paul KW7Y Baldock wrote:

I built a GS35B amp a few years back to be used with my home brew AM rigs. Initially I set the idle current at around 110mA/4KV requiring about -35V bias. Over a few years of very little use the idle current drifted up so I increased the bias voltage to get it back down. Eventually I was up to -55V with the idle current at around 180mA, and so I installed another tube (purchased at the same time as the first). Same deal as before, started at -35V, now at -55V.

Is this 2 bad tubes, or could I be doing something wrong? I'm getting ready to install a third tube purchased from a different source.

  It is possible that the grids are being damaged (by too much drive ?)
rendering less grid wires to control the electron beam.
--
  Ron  KA4INM - Youvan's corollary:
                Every action results in unwanted side effects.
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