[Amps] Checking Filament Voltage

[Steve Wright]

On 20/02/17 06:00, Roger Parsons <ve3zi at yahoo.com> wrote:
> [...] Is it permissible to run the tube with only filament voltage and no air for a short period? If so, what is a short period?

The filament current draw and corresponding terminal voltage will vary 
according to filament temperature anyway, so if you do run it for a 
short time, then at full temperature it will be different again.

When I wound my GS-35b filament transformer I added taps in the 
secondary for soft start (also used a standby/quickstart, and also 
filament low/operate/high/highest.  I don't know that there was any need 
to make it more finely adjustable than that.

A PWM arduino controller would be interesting (and probably unreliable), 
but my old TL-922 has been given a solid workout over the years and it's 
meter lamps vastly out-lived the tube filaments.


Steve