811 tube coil

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

Original poster: "rheidlebaugh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>

Steve: for a tube to work you must supply + voltage to the plate and ground
return to the cathode /fillament. A reverse bias or - voltage is applied to
the grid to controle current through the tube. A tube is a normaly on
devise. A transistor is normaly off and must be forward biased to turn it
on.
     Your schematic shows B+ voltage to the ground and plate via the coil,
but no - voltage to the filament/cathode. There is - 2500v applied to the
control grid via the diode, but not to the fillament/cathode. You are
missing a connection and a resistor, probibly at the R to fillament with a
5K or so resistor connecting L3/R junction to the grid. The high wattage
resistor should go to the fillament not the grid. I do not know what is ment
by the term " sputter mode" of opperation  as this is not a normal tube term
. Sputter mode is usualy a term used in vacuum deposition and would refer in
a tube to distruction by excess current.
    I hope this helps. your curcuit uses a - supply voltage to make the coil
safer. My coil uses + voltage and no safe way to touch any part of the
primary. My secondary is grounded to earth ground. My 811 coil was made in
the early 1950's and with high use is still working well.
   Robert  H