On Wed, 6 May 98 07:40:26 -0800 Rich Measures <measures@vc.net> writes:
SNIP
>
>The problem at hand is that gas is Not being detected in 3-500Z tubes
>with bent filament helices.
>
>Until recently, I owned some new 4E27 pentodes that were manufactured
>in
>the 1940s. Some of them still exhibited good vacuums, however other
>4E27s from the same lot were quite gassy, presumably due to imperfect
>metal/glass seals.
Are you now confusing or mixing up "gas" Rich. Gas due to imperfect
seals is not the same as gas released internally from the materials.
I also suspect that your microamp hipot tester will not be capable of
creating the conditions necessary to recreate a gas discharge event...but
I will leave that to Arlen and others with a formal education to comment
on.
Again, it may sound like I am asking old or dumb questions, but I am
>
>>>relatively new to this group (couple months) and haven't heard all
>the
>>>answers before. And as I pointed out before, I am not an expert on
>tubes.
>>
>>Being new to the group may explain lack of expertise on tubes, but it
>
>>does not explain absence of knowledge of undergraduate physics.
AMEN!
>>
>>Sorry to be so rough, Jon,
Sometimes it takes a 2x4 approach to get a persons attention Arlen. I
think your message was well put and I know that I learned from it.
........
>
>I concur that Jon erred on the carbonization of arc-marks matter,
>Arlen,
>however, perhaps You would like to proffer a scientific explanation to
>
>the [AMPS] group on how/why the filament helices in a 3-500Z can be
>suddenly bent by a "gas discharge" or "barnacles" -- even though the
>grid
>is grounded -- even though no arc-marks can be found at autopsy --
>even
>though the VHF suppressor resistor has more than doubled in resistance
>
>without exibiting cosmetic damage?
As has been mentioned here numerous times...how do you know the condition
of the resistor minutes, days or weeks before the arc? Unless you can
recreate the event in a controlled experiment I fail to see why you
continue to harp on the resistor.
In the case of the SB-220 would not the almost instantaneous discharge of
the 3200VDC ( in standby which is where most arcs appear to occur) not
cause damage to the resistor? Would not the field developed in the
suppressor L be sufficient to "bend" the carbon in the resistor causing
the case to crack? If one were to believe that the magnetic field caused
the filament to bend then the same reasoning would hold for the
resistor...at least it makes sense to this uneducated dummy.
Rich has also failed to ever explain how an amp in standby, biased well
beyond cut-off can suddenly have a parasitic event. Particularly in an
amp that is completely stable when keyed with no drive and the Tune and
Load caps are varied in an attempt to force a parasitic.
Not to be confused by external arcs in tank circuit components while the
amp is in a RF amplifying state.
73 Carl KM1H
>
>
>cheers
>Rich...
>
>R. L. Measures, 805-386-3734, AG6K
>
>
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>
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