Bruce, it is possible to tie one side of the filament circuit to ground
return and it may work in some cases. In my own experience this caused
objectional hum to be superimposed on the RF output signal of the amplifier
tube. There is a "trick" to get around the problem of not having a
center-tapped filament transformer. Find another low-voltage transformer with
a center-tapped winding with a current rating somewhere in the range of 1 or
2 amps, maybe a filament transformer from Radio Shack with a 12 volt winding
@ 1 or 2 amps. Then parallel this winding across your present filament
transformer terminals, do not connect the primary winding to anything, just
let this second transformer "float" across your filament transformer
terminals. Then connect the center-tap of this winding to your ground return,
and it will act just like a center tap for your original transformer. 73,
Todd WD4NGG .
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