-★ 1, if you are sure.

"Check whether the magnetron, high voltage diode, capacitor and transformer are normal."

You should check whether the primary winding of the transformer has working voltage? As long as the rated voltage is applied to the primary winding of transformer, the microwave oven will be heated.

-★ 2. You can lead two wires from the primary winding of the transformer, close the metal shell (to prevent microwave leakage from hurting people), and turn on the switch for measurement (pay attention to safety). If there is no voltage, it is a fault of the control circuit board.