H0
Oster
High-voltage system overload or magnetron fault
Microwave displays H0 or HO and does not heat; may be accompanied by a humming sound.
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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
Shorted magnetron, Shorted high-voltage capacitor, High-voltage transformer overload, Internal arcing in waveguide
How to Fix / Troubleshooting
Safety first: Unplug the microwave immediately. Do not continue to operate a unit that hums loudly or smells burnt. High-voltage repairs are not DIY-safe.
- External checks only: Verify the outlet and circuit are not overloaded. Do not use extension cords.
- Inspect for burning smell or smoke: If you notice any, discontinue use permanently until inspected by a technician.
- Professional service required: H0 typically indicates a serious high-voltage fault. A technician will test and possibly replace the magnetron, capacitor, diode, or transformer with Oster-approved parts.
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Repair Difficulty
Professional Required
5/5
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