Some of the old generators and receiver magnets has lost their magnetisation and had to be re-magnetize.
Tools for doing it can not be bought from shop, so I made one for me.
In yellow wooden box has only the U-shape bend transformer plates and winding around it.
I use adjustable transformer for voltage (current) adjustment (voltage from 0 up to 260 V) and the box with meter has rectifier, capacitor + coil for filtering.
Magnetization need DC current !
The generator with 4 magnets can be place between the jaws of the coil.
Then just rice the voltage the wanted level and slowly back down to zero.
It you like you can hit magnets with small hammer when the power is on, this help them to keep the magnetisation.
Three magnets does not need the full power of the device, you do not have power to the turn the crank any more !
Be careful with old magnets, do not drop them, their will loose the magnetization !