[Amps] One PS, many amps

[Ian White G/GM3SEK]

Gary Schafer wrote:
>
>
>>
>
>I should have posed the question differently. What I was really asking 
>was: What about applying high voltage to a tube when the filament is 
>not  powered up? Isn't that harmful to the tube?
>
As far as I know, high voltage itself is not harmful to the tube in any 
way. What is actually harmful is a demand for more electron current than 
the filament or cathode is capable of emitting, because it is not fully 
up to temperature. So the tube remains safe with HV applied if:

* the filament/heater is switched off and cannot emit any electrons at 
all; or if

* the amplifier is not allowed to transmit while the filament/heater is 
heating up or cooling down - in other words, the normal RX-state cutoff 
bias is applied (resistor-type cutoff bias will meet this need).



-- 
73 from Ian G/GM3SEK
http://www.ifwtech.co.uk/g3sek