The electric oven in my apartment decided, while it was turned off, to fill the place with foul smelling smoke.
I suspected a thermal switch fault.
So I took it apart, obviously. Interesting fault, with 2 layers of insulation failing.
The chassis cooling fan appears to be on a switched negative circuit, with the coil live and arcing to ground via the motor frame.
It's a shaded pole motor, so there's a single winding of enameled wire on an insulated bobbin, but both the winding insulation and the bobbin have failed, allowing mains to constantly arc to the oven chassis, eventually heating the coil and bobbin up to smoking temperature.
No idea how long until the landlord replaces it, so need a solution now.
As the winding appears to still be conductive, and able to run the cooling fan I just need a way to power it that's not referenced to Earth! Watch below to see how I found out it wasn't the fault I expected, and how I can still cook pies.