Necchi Supernova machines have an electrical block regulating the current to the motor and the lamp. Necchi Supernova Julia has a somewhat different block, see Dan’s post.
Here is the underbelly of a 1955 Necchi Supernova flat bed with the electrical block at its right end. This is the European version of the “First Edition”, i.e. the Supernova mark 1, the first version to come out.
The block contains an AC/AC voltage converter for the motor, another one for the light, a mighty capacitor and the motor and light switches.
There is a socket on the bottom where you can plug in the pedal for the in-table or free arm version, or where you plug in a lead to a socket mounted in the back wall of the case for portable models.
The above block is for European distribution, so it converts voltage from 200V, 220V or 250V – the voltages used in different European countries in 1950s when this machine was made. The motor in my Supernova is rated at 220V, so this transformer converts all current to 220V. Models meant for USA have a similar block, and probably a different motor.
The light runs at 12V AC. There is only one wire going to it, and the return current is routed through the body of the machine. Forgive me if I don’t like it. 🤔
The capacitor in my flat bed Supernova burned out.
Since my Supernova’s motor takes 220V which is roughly our mains voltage, I removed the whole block and wired a socket directly to the motor. We have plenty of household appliances and other sewing motors rated for 220V, and they are all doing fine.
Note: later Supernova models used 160V motors even for the European editions, so you need that transformer there, you can’t just wire that to your 240V mains! Always check your own motor first!
But some people prefer to keep the original kit 😉, and for them here’s how you wire the plug.
The grey wires run to the pedal. Black is neutral, red is line, green is earth.