Buzzing or Humming Circuit? Troubleshooter
Some hum is normal. Some is a warning.
If there's a burning smell or heat, switch off first. Work through one question at a time. You can go back or start over whenever you like.
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Safety: this troubleshooter is general information for low-voltage DC learning circuits. 240V AC mains can kill: in Australia, work on mains wiring must be done by a licensed electrician. Disconnect power before you touch wiring.
