Specifications

Ver SG 9/200 24 Sharp Electronics Corporation
The resonate cavities are so designed that the movement of electrons will be only allowed
at the frequency of 2450 MHz. The positive and negative fields created as the cloud
passes one cavity to another will create the pushing and pulling of the electrons all the
way to the antenna. As the antenna gets moving within, it will generate electro-magnetic
energy, at the frequency of 2450 MHz. This is the RF energy that is used by microwave
ovens.
A symptom of a failed magnetron is a no heat complaint. After confirming the power
supply has not failed, unplug the unit and remove the wires from the terminals of the
magnetron. With an ohmmeter check the resistance of the heater on the cathode. The
reading should be about .25 Ohms. If the resistance is infinite the heater is open. This of
course would not allow the electrons to boil off the cathode surface. Without the cloud of
electrons in the vacuum area the tube can not generate energy within the resonate
cavities. The magnetron would have to be replaced to correct the problem.
Next, with an ohmmeter check from the magnetron terminals to the case of the
magnetron. An infinite reading would indicate the tube does not have a cathode to anode
short. If a short existed between the cathode to anode the electrons would go directly to
ground, taking the path of least resistance. This of course would again mean the cloud of
electrons needed within the tube was not present and the tube would not generate energy.
Any resistance reading at this point would warrant replacement of the magnetron.
The last test that can be taken on the magnetron is a visual check. Check the magnetic
rings that are around the anode for a break. If the magnets are broken they will prevent
the spherical movement of electrons in the vacuum area of the tube. All the electrons
will align themselves up to a North Pole that was developed at the break. Again without
the movement of the clouds of electrons past the resonate cavities, the tube will not
generate energy. The magnetron tube would have to be replaced.
Some failures within the magnetron can not be detected with the use of meters or visual
inspections. These types of failures must be diagnosed via process of elimination. Check
all other possible causes for the tube not to operate, if no other reason is detected, replace
the magnetron. An example of this type of failure would be a gassy tube. This condition
occurs when the vacuum is lost within the tube. The introduction of various gasses will
cause friction due to the electrons hitting the electrons from the alien gasses. The heat
generated from these collisions will super heat the cathode causing deterioration of the
cathode. The tube will first emit too much power and the customer will complain of food
over cooking. Then it will very quickly reverse symptoms and have low or no output.
This condition of extra heat is usually the reason why the magnets will crack.