Microwave display and lights work, but when START is pressed there is no heating and no usual humming sound from inside; timer counts down normally.

Critical safety warning: The high-voltage section of a microwave (transformer, capacitor, diode, magnetron) operates at extremely dangerous voltages. Do not attempt to probe or work on these components unless you are trained and equipped. In many regions, only licensed technicians should service this area.

Basic user checks (no cabinet removal):

• 1. Confirm symptom: Place a microwave-safe cup of water inside and run for 1–2 minutes. If the water remains cold and you do not hear the usual low humming, the high-voltage circuit is likely not energizing.
• 2. Check power settings: Ensure the power level is not set to 0% or a very low level. Reset to 100% and test again.
• 3. Perform a power reset: Unplug the microwave for 5 minutes, then plug back in and test. This can clear a latched relay or control glitch.

Technician-level checks (for professionals only):

• 4. Inspect high-voltage fuse: With the unit unplugged and the capacitor safely discharged, locate and test the high-voltage fuse near the transformer. Replace only with the exact type and rating specified for Sage microwaves.
• 5. Check transformer primary: Test continuity of the transformer primary winding. An open winding indicates a failed transformer that must be replaced.
• 6. Verify control relay output: Confirm that the control PCB is sending power to the transformer when heating is commanded. A failed relay or PCB track may require control board replacement.

Because of the high risk, most users should not attempt internal high-voltage repairs. If basic resets do not restore heating, contact a Sage-authorized service center.