[Top] [All Lists]

[AMPS] SB-1000 mods?

To: <>
Subject: [AMPS] SB-1000 mods?
From: (2)
Date: Wed, 12 Sep 2001 21:01:44 -0700
>2 wrote:
>>>2 wrote:
>>>>//   The purpose of the glitch-R is to protect the electron tube from 
>>>>failure during an intermittent oscillation condition. 
>>>Make that "...from failure due to a current surge occurring for *any*
>>//  Please name and explain some other causes of potentially fatal 
>>current surges, Mr. White.
>You appear to have forgotten that this very subject was discussed at
>some length back in January/February. 
//  Alzheimers?

>Here are a few quotes from the literature.
>"Although a very high degree of insulation between two electrodes can be
>obtained... by modern high-vacuum technique, it is nevertheless possible
>for this insulation to break down spontaneously and completely. This
>phenomenon is known by various names, such as... the "Rocky Point
>effect", after the American wireless station, which is one of several at
>which it has been observed. ...  Time lags [after application of
>voltage] can vary between a few seconds or minutes to tens, hundreds or
>even thousands of hours." 
>Gossling (British GEC), 'The Flash-Arc in High Power Valves', 1932.
//  What of G.W. Fyler (Sept.,1935) article in the IRE Journal - 
"Parasites in Transmitters"?  

>"Most power tubes are subject at some time to a phenomenon known as the
>Rock Point effect, which derives its name from experiences with power
>tubes in communications transmitters at Rocky Point, Long Island.

//   22kV is X-ray-land, so at 22kV, perhaps.  At 4kV, it seems unlikely 
because I have done a number of autopsies on 8877s, 8874s and 3-500Zs and 
I found no barnacles or arc marks.  I am doing two 8877s this week.  I 
will publish the photos on my Web site unless the tubes died from leaky 
ceramic/metal seals or an open heater.. 
>This phenomenon manifests itself as  an internal flash-arc developing
>with little warning on power tubes which apparently are of good design
>and operated in a conservative manner... The cause of this phenomenon is
>not thoroughly understood..."
>Parker and Hoover (RCA), 'Gas Tubes Protect High-Power Transmitters',
>"An arc is a self-sustaining discharge of electricity between electrodes
>in a vacuum environment...  Since any high voltage vacuum device may arc
>at one time or another..."
>Eimac, 'Fault Protection', Application Bulletin #17, 1987.
>Those are only about the arcs that can occur *inside* tubes. 

//  Do you think this could cause gold evaporation from the grid or a 
bent filament?

>Current surges can also occur due to HV shorts outside the tube - remember the


> These outside surges will not damage the tube but they can
>certainly damage the power supply and metering circuits.
>As I said, it's best to keep an open mind about the causes, but by all
>means protect against the effects.
amen,  Ian

-  R. L. Measures, 805.386.3734, AG6K,  

FAQ on WWW:     
Administrative requests:

<Prev in Thread] Current Thread [Next in Thread>