Oster
No heat / magnetron circuit failure
Microwave runs but does not heat food; turntable rotates and interior light is on, but food remains cold.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Failed magnetron, Open high-voltage diode, Open high-voltage capacitor, Faulty high-voltage transformer
How to Fix / Troubleshooting
Safety first: Unplug the microwave immediately. The high-voltage system is extremely dangerous. Do not attempt internal high-voltage repairs unless you are a trained technician.
- Basic user check: Confirm you are not using a demo mode (if your Oster model has one) and that you are setting a normal cook power level (e.g., 100%).
- Test with water: Place a microwave-safe cup of water inside and run for 1–2 minutes. If the water is still cold, heating is not occurring.
- Do not continue to run: Operating a microwave with a failed high-voltage system can cause further damage.
- Professional repair: A technician will test and replace the magnetron, diode, capacitor, or transformer as needed using Oster-approved parts.
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Repair Difficulty
Professional Required
5/5
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