Which are the calculations to be done to determine the consumption of a tube ?

[kagliostro]

I'm interested to know which are the calculations to be done to determine the consumption of a tube

assuming B+ is 315v

which is the consumption of V1 (ef86) in the Vox AC15 ??

How to calculate the consumption ?

Many thanks in advance

Kagliostro

[DummyLoad]

calculate current thru anode resistor; IRa. given B+ and Va so then VRa = 315V - 80V = 235V  calculate current thru Ra = 235V/220K = .00107A or 1.07mA = IRa = Ibias

calculate Vg-k 2K2*1.07mA = 2.35V

calculate Vtube = Va - Vg-k = 80V-2.35V = 77.65V

calculate Pdiss = Vtube*Ibias = 77.65*1.07mA = 83mW

so then Pa = 83mW

what i do most times is ignore Vg-k calculation w/ small signal tubes since it's usually a couple of volts or less. you need to take it into account on cathode biased output stages though, as it can be a significant quantity. in fixed bias, Vtube is measured to Va to gnd.

[kagliostro]

MANY THANKS ISOTone

Kagliostro

[kagliostro]

I've read slowly and with attention the given explanations

one thing is out of my comprehension

given B+ and Va so then VRa = 315V - 80V = 235V

What Va means ?

from were comes the 80v value ?

Va (used as an abbreviation) isn't the max anode permitted B+ voltage ?

Sorry for the neavity but need further explanation

Thanks

Kagliostro

[Geezer]

What Va means ?

from were comes the 80v value ?

I believe Va = Anode, or plate voltage

The 80v comes from your attached drawing, showing 80v present @ the anode/plate

[kagliostro]

MANY THANKS Geezer

The 80v comes from your attached drawing, showing 80v present @ the anode/plate

 

Sometimes I act as a real stupid

 

I've find the AC15 schematic, but was really not well readable

so at the last moment I posted another schematic that I've find to have a good readability

but didn't read it with attention

Sorry - I APOLOGIZE

This happens when I try to do more than one thing at the same time SORRY 

Kagliostro

[PRR]

[kagliostro]

MANY THANKS PRR

your schematic clarify the issue further

Kagliostro