Baird T5 restoration project.

[Geordie McBoyne]

Here's my suggestion on how the Baird T5 sound demodulator works.               The 41.5mc/s TV sound is supplied to the signal grid of the FC4 octode G4 .  Along with the 100,000 ohm resistor and 0.00005mfd capacitor normal leaky grid detection takes place.  The resultant audio signal developed between G4 and the cathode is modulated by the 200Kc/s local oscillator. The 200Kc/s component is filtered out by the pi circuit comprising of the 20mH coils and 0.0005mfd capacitors.                                                                                                       It could be said the circuit operates in a similar manner as the bias oscillator in tape recorders.

Geodie McBoyne.