On Wed, 29 Oct 2003 19:54:51 GMT, Allen Windhorn
wrote:


If I did this I would put a 0.01 uF capacitor to ground at each
filament pin, to keep RF from propegating through the wires. I would
also put a resistor to ground somewhere in the string to bleed off any
stray leakage current (maybe 1000 ohms or so), otherwise you might get
voltage buildup that could cause problems.

In many audio amplifiers, the filament was powered from a 6.3 V
winding with a grounded centre tap. If the centre tap was not
available, a potentiometer was connected across the filament winding
and the wiper was connected to ground and the wiper was adjusted for
minimum hum.

In RF applications, using bypass capacitors to ground at each tube is
a good idea.

Paul OH3LWR