How can I fix my Kenwood A701A food Mixer?

UNPLUG IT!
Turn the beast upside down. Look through the plastic grille beneath the motor, you should see electric entrails, capacitors resistors & wires. Turn the speed dial, and you should see the guts behind the grille move up and down in sympathy.
If they do, look carefully at the grille on the side farthest from the dial. You are looking for a pair of hexagonal screw heads for a slotted screwdriver. These are about 30mm beneath the plastic cover, about 60mm apart. One has a hole, the other uses one of the vent slots. A suitable screwdriver will reach both without having to take anything apart. To adjust speed, turn each an equal amount. Clockwise slows. Try a couple of clicks at a time and try it out. UNPLUG EACH TIME YOU ADJUST, DARWIN AWARD AWAITS OTHERWISE.
If the guts didn't move, then it may be a bit too complicated to sort..
Good Luck.

Fred Bloggs
November 2007