Goldstar MA-2005ST service manual Microwave generation systemMagnetron 2/2, Testing Magnetron Tube

4-4. Microwave generation system_Magnetron (2/2)

ANTENNA

ELECTRONS

2,450 MHz.

CATHODE

* In order to create an electron flow from cathode to anode, the cathode must

be heated and a potential difference must exist between the two.

This is accomplished by heating the cathode with 3, 4 to 3,5 V AC. ( from the

filament winding of the high voltage transformer) and applying a negative

4000 V DC (from the voltage doubler circuit) to the cathode.

* Originally the electrons would travel in a straight line from the cathode to the

anode. However, with the addition of a permanent magnet surrounding the

anode creating a magnetic field, the electrons travel an orbital path between

the cathode and anode. As the electrons approach the anode, their orbital

path takes them past small resonant cavities that are part of the anode.

The passing notion of the electrons induces electron current to oscillate in the

ANODE	PERMANENT￿
	MAGNET

resonant cavities at the very high frequency or 2,450 MHz.

This RF (Radio frequency) energy is then transferred to the antenna.

TESTING MAGNETRON TUBE

*Disconnect power, remove the wrapper, and discharge the capacitor.

*Remove the two leads from the magnetron terminals.

*Connect the ohmmeter between one terminal of the magnetron and the outer case of the magnetron. If the ohmmeter reads infinity, go to below. If the ohmmeter reads less than infinity, the magnetron is shorted.

*Connect an ohmmeter across the terminals of the magnetron. The ohmmeter should read less than one ohmf the ohmmeter reads over one ohm or infinity, the tube is defective.

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