18-11-2016, 04:07 PM
(This post was last modified: 18-11-2016, 04:08 PM by Mike Watterson.)
(18-11-2016, 08:30 AM)pwdrive Wrote: Question, does that mean that when it's pentode connected that the screen voltage is obtained from a different supply than the anode, if so why ?Ideally the Screen is either from a fixed HT or decoupled with a capacitor. It's only the same as anode volts in Triodised mode.
If decoupled, then the average screen current (and thus voltage drop from HT via resistor) is constant.
The "high" screen voltage "hides" the dropping anode voltage from grid. (Lies but suffices).
A beam electrode or a suppressor grid is needed (Pentode vs Tetrode) because at a low anode voltage the electrons might get attracted back from Anode to g2, causing the "kink" (Hence KT = Kinkless Tetrode, a Pentode done with electron lens, the "earthed" beam forming plates do same function as suppressor grid (suppressing secondary emission).
Triodised gives more power, none is wasted on the g2 / screen
