Ive just had the same problem , lots of white smoke and a horrible burning smell.
Took the chef to bits , which wasnt too difficult , maybe 4 screws and a couple of springs and found one of the capacitors had cracked and fallen to bits , and smelled of burning.
Quick visit to ebay , typed in
kenwood chef repair kits and there they were. £6.00 all inc.
All i have to do now is solder them in and save myself a couple of hundred pounds
Simple.
Alan spedding
July 2010