Re: Ekco T221.
As I expected there is no drive to the grid of the 20P4 line output valve.
The line multi-vibrator consists of one section of a 20L1 double triode and the screen grid of the 20P4, that forms the oscillator start up circuit. When fully functioning oscillator feedback takes the form of a 15pF pulse capacitor connected between the grid of the triode and a tapping on the line output transformer.
DFWB.
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