Sorry to bore everyone with this, but i need some help.
Am i thinking correctly here:
I have 100K plate resistor, 120 - 68 = 52V
Which is too low..
So to adjust the plate voltage to 50V i need to adjust the plate resistor. Right?
How do i calculate that? Or is it trial and error thing..?
it will really be only if you put a AC701K in there that you will obtain those precise results,
this is why the self bias is a no brainer but the b is much more fun and learning,
I have 100K plate resistor, 120 - 68 = 52V so this mean 52V drop trough 100K means 0.52ma, U= RI
52V/100K = i in ma
here is an example,
B+ = 115V
Plate = 53V
Drop across 100k (plate resistor)
= 115-53 = 62V Voltage drop across 100k
that means the tube running at .62ma
We want about 45V on the plate to get to
the specified 0.7ma then
the best at this point is to replace temporarly the plate resistor with a pot lets say 250K and try to tweak both bias pot and plate resistor pot until you find the nearest condition , no one uses same tube and this is a related together and the 2 parameter are related, this is the best approach once you find the sweet spot for it you can replace the plate resistor whit with a 1/4 watt resistor ,
try that and keep me posted and let me know what the balance value you find or the nearest , what tube did you used, and make sure you try the mic first.
Let me know,
Best,
dAN,