B-18 PI Question

[jon]

What are the power tube plate and screen voltages?

Here is my bias spread sheet that has all my pt voltages.

BTW the 1000 ohm screen resistor is common to both tubes

[Structo]

I'm not sure I understand your XLS table.

That is for a cathode biased amp.
Isn't your amp fixed bias?

[jon]

Ignore the title of the spread sheet. The form works as long as you have a resistor on the cathode to ground, in this case 1ohm.

Yes the amp is fixed bias.

Here are the numbers you were looking for:

Cathode Current: 56mA per tube
Voltage drop across the common 1K screen resistor 17v (474 in 457 out)
Screen Current: 17mA
Plate Current: 39mA (Cathode Current minus the Screen Current)
Plate Voltage: 470v
Each tube is idling at 18.32W (52.37% Plate dissipation on a 35W tube)

[martin manning]

Jon, if the 1k screen resistor is common your screen current per tube is 17/2, so Pa is 22.33W... 64%

[jon]

Thanks I hadn't figured on that.