Powr Supp Drop Resist

[trem]

I tried looking this up. I have attempted before, but have always come up wrong.
Is there a way to estimate the Ohm value of dropping resistors in the B+ line.?
My PT is 300-0-300.
Rectifier is 6X5
That is into a Pi Filter.... 20/450 - Choke - 10/450
Can I somehow estimate the drop resistor I will need to get 200-250 volts for the 6SL7 phase inverter.?
Can I use the B+ potential from the screens, and the listed (is it maximum) plate current of the 6SL7 (2.5mA) to get a rough idea of the resistor I will need between the Screen and Phase Inverter nodes.?
Thank You

[bob p]

Check out Duncan's amp pages for the PSU Designer 2 software for windows. It will allow you to model the power supply and graphically visualize the voltages it produces over time. You can change components and see how the changes alter the plots of the power supply waveforms. A very handy tool.

[R.G.]

Almost as good as an online calculator app is knowing that V = I * R for all resistors, all the time.

If you know how much current goes through a resistor and the resistance, you *always* know what the voltage drop across it is.

If you know how much voltage you want to drop and how much current flows, you *always* know what the resistance to make that wish come true is.

If you know how much voltage to drop and what resistance you have, you *always* know what current will make that come true.

[Enzo]

^^^What he said.

Ohm's Law will tell you. If you have to power two sides of a dual triode, that is two triodes, and if they draw 1ma apiece, then you have 2ma of current. If you have 400v and want 250v, you need to drop 150v at 2ma, and in that example, Ohm's Law tells us. R=V/I=150v/0.015A=10,000 ohms=10k.

[trem]

Hey -
Yeah.....that is what I was trying to ask.
If I know there is (just round numbers) 250 VDC on the screens, can I use the tube data (2.3mA) to calculate what the resistance Will/Would be.?
Or at least in the ballbark...to get started.

Sorry if I am missing it. Is the 2.3mA for each triode.?
Thank You
NJ7P SQL Tube Database Query

[madkatb]

Check out page 5.
http://www.diyguitarist.com/PDF_Files/j_darr4.pdf
Yes, that is 2.3 mA per section (per triode).

[trem]

Bob
RG
Enzo
Mad...
Thanks Again.
The help is much appreciated.
Makes my job better and easier; makes me a much Smarter/Better Informed amp hack.
best