Re: 4-125A, vacuum tube do's and donts

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

Much of Eimac tube book is on the web.... the company is now called CPI
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, April 09, 2002 7:00 PM
Subject: Re: 4-125A, vacuum tube do's and donts


> Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<evp-at-pacbell-dot-net>
>
> Tesla list wrote:
> >
> > Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <Fucian-at-aol-dot-com>
> >
> > In a message dated 4/8/02 1:49:53 PM Eastern Daylight Time,
tesla-at-pupman-dot-com
> > writes:
> >
> > << Matt,
> >
> >  You are wise to ask this question, since tubes are susceptible to
> >  destruction in various ways.  First of all, never let the filament
> >  voltage go more than 5% over the rated voltage.  Never let the
> >  plate get too orange-red.  An orange red color is normal, but
> >  you don't want it to get orange or yellow.  A good way to run
> >  the 4-125A's is to tie the both grids together and run them as
> >  a triode.  Circuit values have to be correct for that.  Use a
> >  plate lead choke/resistor to prevent tube damage in the event
> >  of an internal arc-over.  This tube can acually withstand a higher
> >  plate voltage of 4kVAC or so.  All the adjustments are critical
> >  for best results in a VTTC.  This tube can give a 12" spark or so.
> >  Run the tube only in an upright position.  If the tube gets very
> >  orange, but the spark output is weak, then things are not adjusted
> >  correctly.
> >
> >  cheer,ss
> >  John
>
> I'm worried about the recommendation to tie the grids together and run
> the tube as a triode.  Has anybody checked with Eimac to see if this
> mode of operation is OK?  With some tubes it is, but with others may
> result in damage to the screen.  I can't find my Eimac book "The Care
> and Feeding of Power Tetrodes", which has information on the subject.
> Maybe someone else has one.
>
> Ed
>
>
>