If countdown is processing, a glass tray is turning and normally sounds produced, then the problem is in high-voltage unit of the microwave. One of the parts got broken: magnetron, transformer, high-voltage diode, step-up circuit capacitor. Magnetron thermostat or one of safety switches may also be broken, or electronic control board relay malfunctions. It is impossible to determine a specific broken part without a diagnosis and we are ready to repair your microwave.