>
>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*
>>>reason."
>>>
>>// 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',
>1956.
>
>"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
>earwigs?
Yes
> 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, www.vcnet.com/measures.
end
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