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FERNSEH · 18th Jul 2016, 5:20 pm

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.

18th Jul 2016, 5:20 pm	#7
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	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.