PURPOSE: To increase the freedom in designing of heater coil by adjusting the capacity of a current controlling capacitor connected in series to a cathode filament.
CONSTITUTION: As a current controlling capacitor 25 is connected in series to a heater coil 24, a filament current If runs in a series resonance circuit formed by the capacity of the capacitor 25, chalk coils 19, 20 of a magnetron 16, and a magnetron filament 17. The impedance of the resonance circuit at that time is changed according to the capacity of the capacitor 25. Thus, the current If is adjustable by the capacity of the capacitor 25. The capacitor 25 is provided in the middle of a booster transformer 21 and the lead wire of the magnetron 16, whereby the designing freedom of the heater coil of the transformer 21 can be increased. Namely, the current If can be roughly adjusted by the coil 24 of the transformer 21.
MAEHARA NAOYOSHI
BETSUSOU DAISUKE
