Hi @prishen ,
Here’s the circuit diagram for the mixer taken from the [http://www.britishexplorers.com/Kenwood%20gearbox/A701a%20service%20info.pdf|service manual]
The motor operate circuit seems fairly straightforward. Power connects through the switch to operate the motor, so most probably a wire came loose or a connection was broken when you removed the electronics.
''Testing with the power disconnected'' using an Ohmmeter should help to track down where the problem is.
[image|2077090]
(click on image to enlarge for better viewing)