Swan microwave humming but not heating?
Hoping someone can help with my Swan microwave (SM22070BN) — loud hum and no heat, which I've read points to the magnetron. Grateful for any pointers, thanks.
1 Answer
A loud hum with no heating often does point to a fault in the high-voltage side of the microwave, but it is not always the magnetron itself. On these, the capacitor, diode, transformer or magnetron can all give similar symptoms.
Before doing anything, isolate the microwave from the mains. Microwaves contain a high-voltage capacitor that can retain a dangerous charge even when unplugged, so internal checks are not suitable unless you are properly trained.
A few sensible checks:
1. Confirm the symptom clearly Heat a mug of cold water for 1 minute. If the turntable, light and fan all run normally but the water stays cold while the unit gives a deeper/louder hum than usual, that does strongly suggest a high-voltage circuit fault.
2. Check for burning smells or visible damage If there has been any burning smell, arcing, or scorching inside the cavity or around the waveguide cover, stop using it. That can indicate a different fault from a simple magnetron failure.
3. Consider the age and value of the appliance On many Swan countertop models, repair can be uneconomical once the fault is in the high-voltage section, especially if labour is involved.
4. Do not replace parts by guesswork A magnetron is a common suspect, but the HV diode and capacitor are cheaper parts and can also cause no-heat/humming faults. Proper diagnosis needs safe testing procedures.
Because this involves mains and high-voltage components, I’d recommend a qualified microwave engineer rather than DIY internal repair. If you want, I can help you decide whether it’s likely worth repairing based on the microwave’s age and condition.
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