If either your top or bottom wheel is spinning at high speed when your machine is turned off, you will be able to stop it by turning off the master switch under the machine. This usually happens when certain components on the motherboard have broken (can be caused by a major ball jam).
The only way to repair this problem is to contact your local Spinfire distributor for a replacement motherboard or ask your local electronics expert to repair it.
The components on the motherboard are Q2 (bottom) and Q3 (top) and the replacement component part number is IRFB3206.