What part do I require to fix G75C Indesit Tumble dryer?

Tumble dryer makes a humming sound when start button is pressed and drum will not turn. When top cover is removed (I am a qualified Electrical Engineer) assisting the drum it will start to turn and dryer works as normal. Is it the voltage regulator/Suppressor at back R/H side that requires replacing or the starter relay in the front of the machine? Many thanks. Neale.