Electrolux Cyclone XL, Repair the Power Control?

Ref: Electrolux Cyclone XL, model ZCX6470 (but it seems that all XL are similar and model number is country dependent)

Hello,
We have two of these machines in the family. Both with same exact problem. The (adjustable) Power Control is out of action. Machine will operate well when connected to electricity but control is not active. Must plug in/out to elect outlet for on/off operation.
Can this be repaired? How? (or must replace the control?)
Thank you for your help.
GD