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

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

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
  >>
Also,any way to hold the filament at 5volts?Maybe I could use a regulator for 
DC?I could rectify the output and feed it into a regulator circuit for 5volts 
dc.It would need a lot more though since it will pull 6.5amps.Also, it says 
it draws 6.5 amps.Does that mean it DRAWS that or thats the MAX and goinmg 
over kills it?Would it be wise to limit it to 6.5amps and no more?I hear its 
thoriated tungsten.Is there a special deal I have to do to it?

MAtt