FILAMENT TRANSFORMER
All oscillator tubes require power for heating the cathode (Filament) usually this is a high current low voltage line frequency supply obtained from filament transformers, when a cold filament is first turned on its resistance is much lower than when it is hot. Provision is usually made to prevent the filament current from reaching a too high value when first turned on. We specially design high impedance filament transformer to insure safe operation of oscillator tubes.
