I always thought that a gassy tube is essentially a short when HV is applied,
or perhaps like a thyratron: once current is allowed to flow by the control
grid it can't be stopped until the cathode line is opened. Gas-filled
rectifiers, such as the 3B28, 866A, etc., or the gas-filled VR tubes are
examples. Is there an "in between" state where a tube is gassy and works fine
except for excess plate current?
Kim N5OP
________________________________
From: Bill Turner <dezrat@outlook.com>
To: Amps group <amps@contesting.com>
Sent: Monday, December 1, 2014 11:38 AM
Subject: Re: [Amps] Holding a vacuum
------------ ORIGINAL MESSAGE ------------(may be snipped)
On Thu, 27 Nov 2014 19:15:08 -0500, you wrote:
>What metric does one use to determine if a given tube holds a vacuum or not?>
>Cheers,
>
>Karin K3UU
REPLY:
Tubes that lose vacuum draw excess anode current even when idling and
if they are glass, one can see a blue glow in between the elements
when HV is applied.
73, Bill W6WRT
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