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Re: [Amps] Holding a vacuum

To: Amps group <>
Subject: Re: [Amps] Holding a vacuum
From: Kimberly Elmore <>
Reply-to: Kimberly Elmore <>
Date: Mon, 1 Dec 2014 10:34:21 -0800
List-post: <">>
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 <>
To: Amps group <> 
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?>
>Karin   K3UU


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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